CN100568783C - Bidirectional transmission device and signal transmission method of millimeter wave optical fiber transmission system based on insertion pilot method - Google Patents

Abstract

The invention relates to a bidirectional transmission structure and a signal transmission method of a millimeter wave optical fiber transmission system based on an insertion pilot method. In the present invention, the pilot is inserted into the baseband signal at the sending end of the central station, that is, the intensity modulation of the light wave is carried out with the mixed signal of the baseband signal and the pilot sine wave, and the phase of the light wave is modulated with the swept sine wave, and the Fabry-Perot optical filter is used After the photodetector of the base station completes the photoelectric conversion, the millimeter-wave carrier and the millimeter-wave reference local oscillator carrying the baseband signal are extracted respectively through two millimeter-wave filters with different parameters, so as to realize the downlink function of the system At the same time, the reference local oscillator required for the uplink is obtained in the base station. For the uplink, mix the user millimeter wave uplink signal received by the base station with the reference local oscillator obtained in the downlink to obtain an uplink intermediate frequency subcarrier, and use the intermediate frequency subcarrier to directly modulate the light source in the base station, and the receiving end of the central station After the photoelectric conversion, the frequency is down-converted to take out the uplink baseband signal, so as to realize the uplink of the system.

Description

Bidirectional transmission device and signal transmission method of millimeter wave optical fiber transmission system based on insertion pilot method

technical field

The invention relates to a bidirectional transmission device and a signal transmission method of a millimeter wave optical fiber transmission system, in particular to a bidirectional transmission device and a signal transmission method of a millimeter wave optical fiber transmission system based on an insertion pilot method.

Background technique

In recent years, the rapid increase in wireless communication capacity and business types has made the existing communication spectrum very crowded, and the development and application of millimeter wave frequency bands has become an inevitable development direction. The millimeter-wave communication system has the advantages of rich bandwidth resources, easy frequency reuse, and portable equipment; however, because water mist and oxygen seriously attenuate the signal in the millimeter-wave available window, the transmission distance of the millimeter-wave in the air is limited. In order to achieve A certain network coverage area requires a large increase in millimeter wave base stations, which will lead to a substantial increase in system costs. Using radio frequency fiber transmission technology (ROF) to transmit millimeter waves is a solution to reduce system costs and improve system efficiency. RF optical fiber transmission technology concentrates various functions of signal processing in a small number of central stations. A central station connects several base stations through bidirectional optical fiber links. The base stations are transparent to baseband signals and realize the conversion between light wave/millimeter wave and millimeter wave/light wave. .

The key to realizing the millimeter-wave ROF system is to avoid the influence of fiber dispersion, reduce the cost of the base station, and reduce the weight of its equipment. Specifically, it includes two aspects. One is the generation and transmission of the millimeter-wave carrier in the base station in the downlink, and the other is the generation of the millimeter-wave local oscillator of the base station in the uplink.

In-HouseNetwork Using Multimode Polymer Optical Fiber for Broadband Wireless Services ("Photonic Network Communications" 2003) published by Koonen.T. et al. Broadband Wireless Service Indoor Network Using Multimode Polymer Optical Fiber"), a 5.4GHz downlink structure of optical multiplication is given, and its main research goal is to use multimode polymer optical fiber as the link medium Optical fiber systems generate microwave signals, and this paper does not involve the generation of millimeter waves and the design of uplinks.

At present, there are two main solutions for the uplink. One is to directly modulate the light wave with the microwave signal received by the base station. Although the structure of the base station is simple, when the microwave frequency is high, a high-speed external modulator must be used, which increases the The cost of the base station, and the high-frequency microwave subcarrier will cause a serious impact on the dispersion of the fiber link; the second is to use a millimeter-wave local oscillator in the base station, which is a solution to increase the cost and complexity of the base station in exchange for low-dispersion transmission.

Invention content:

The purpose of the present invention is to provide a way to overcome the shortcomings of the existing two-way link design, to provide a two-way transmission device and signal method for the millimeter-wave optical fiber transmission system of the insertion pilot method, so that the system base station has a simple structure to meet the needs of millimeter-wave optical fiber transmission. practical needs of the system.

To achieve the above object, the present invention adopts the following technical solutions:

A bidirectional transmission device based on the insertion pilot method millimeter wave optical fiber transmission system, the uplink and downlink are formed by interconnecting a central station and a base station through an optical fiber bidirectional transmission link, and is characterized in that:

1), the structure of described downlink is: the laser device in the central station is connected with a phase modulator by pigtail, and a frequency-sweeping sine wave oscillator is connected to the input end of a microwave amplifier by electric lead, and the microwave amplifier The output end is connected to the control electrode of the phase modulator through an electric wire, the output end of the phase modulator is connected to an intensity modulator through a pigtail, and a pilot oscillator and a downlink baseband signal are respectively connected to a combiner through an electric wire Two input ends of the wave combiner, the output end of the wave combiner are connected to the control electrode of the intensity modulator through the electric wire, the output end of the intensity modulator is connected with a Fabry-Perot optical filter through the pigtail, the Fabry-Perot optical filter The output end is connected to an erbium-doped fiber amplifier EDFA through a pigtail, and the output end of the erbium-doped fiber amplifier EDFA is connected to the optical fiber bidirectional transmission link through a pigtail; the end of the optical fiber bidirectional transmission link is connected to a The input terminal of the photodetector, the output terminal of the photodetector are connected to the input terminal of a millimeter-wave amplification splitter through an electric wire, and one output end of the millimeter-wave amplification splitter is connected to a millimeter-wave bandpass filter through an electric wire. At the input end, the output end of the millimeter-wave bandpass filter is connected to port 1 of a three-terminal circulator through an electric wire, and port 2 of the three-terminal circulator is connected to the antenna through a feeder line, and the millimeter-wave signal is transmitted through the antenna to realize the downlink of the signal Transmission function; the other output of the millimeter-wave amplifier splitter is connected to the input of another millimeter-wave band-pass filter, and the millimeter-wave reference local oscillator is obtained at the output of the millimeter-wave band-pass filter, which is the uplink signal The transmission provides a down-converted reference local oscillator;

2), the structure of the uplink is: the user signal collected by the antenna in the base station enters the described three-terminal circulator port 2 through the feeder, is output by the three-terminal circulator port 3, and the three-terminal circulator port 3 passes through The electrical lead is connected to an input end of a low noise amplifier, the output end of the low noise amplifier is connected to an input end of a millimeter wave mixer through an electric lead, and the output end of the millimeter wave bandpass filter outputs a millimeter wave reference local oscillator It is added to the other input end of the millimeter wave mixer through the electric wire, the output end of the millimeter wave mixer is connected to the input end of an intermediate frequency filter amplifier through the electric wire, and the output end of the intermediate frequency filter amplifier is connected to the input end of a laser through the electric wire At the end, the light wave output by the laser is connected to the optical fiber bidirectional transmission link through the pigtail; in the central station, the input end of an optical detector is connected to the optical fiber bidirectional transmission link, and the output end of the optical detector is connected to the One input end of the intermediate frequency mixer, the other input end of the intermediate frequency mixer is connected to the output end of the pilot frequency oscillator through an electric wire, and the output end of the intermediate frequency mixer is connected to an input end of a decision device through an electric wire, and the judgment The device directly outputs the user uplink baseband signal.

A bidirectional signal transmission method based on the insertion pilot method millimeter-wave optical fiber transmission system, using the above-mentioned uplink and downlink bidirectional transmission device of the millimeter-wave optical fiber transmission system for bidirectional signal transmission, characterized in that:

1), the downlink signal transmission method: the phase modulation of the light wave is carried out at the central station with a frequency-sweeping sine wave, the intensity modulation of the light wave is carried out with the mixed signal of the downlink baseband signal and the pilot sine wave, and the intensity and The phase double-modulated light wave is filtered to generate a comb spectrum; at the base station, the light wave transmitted from the central station passes through the photodetector for photoelectric conversion, and then the millimeter wave amplification splitter amplifies the photoelectric conversion signal and divides it into two branches , and then let it pass through two different millimeter-wave bandpass filters, one branch obtains the millimeter-wave downlink modulated wave, and the other branch obtains the millimeter-wave reference local oscillator; the branch obtains the millimeter-wave downlink modulated wave The millimeter-wave downlink modulated wave is amplified and then emitted by the antenna, so as to realize the downlink signal transmission function; at the same time, the branch that obtains the millimeter-wave reference local oscillator provides a millimeter-wave reference local oscillator for uplink signal transmission;

2) Uplink signal transmission method: After the user millimeter wave uplink signal received by the base station from the antenna is amplified by the low noise amplifier, it is mixed with the millimeter wave reference local oscillator in the mixer to realize down-conversion of the signal and obtain The intermediate frequency subcarrier modulated by the uplink baseband signal directly modulates the laser with the intermediate frequency subcarrier, and its output is transmitted to the photodetector at the central station, and then outputs the intermediate frequency subcarrier after photoelectric conversion, and then outputs the user uplink baseband signal through the down conversion and decision device , so as to realize the uplink signal transmission function.

The present invention is further described below: the transmission process and method of the downlink signal are based on the optical frequency sweep method of inserting the pilot frequency, and concrete realization is as follows: referring to Fig. 1, at the central station 1 sending end, frequency sweeping sine wave oscillator 1 -6 generates a sweeping sine wave with a frequency of f _sw , which is amplified by the microwave amplifier 1-7 and drives the LiNbO ₃ phase modulator 1-2 to phase-modulate the light wave output by the semiconductor laser 1-1; the pilot oscillator 1-8 The generated pilot sine wave with frequency f _plt is superposed with the downlink baseband signal 1-10 in the multiplexer 1-9, and the superimposed mixed signal is used to modulate the intensity of the frequency-sweeping light wave. The light wave electric field at the output of the intensity modulator 1-3 is expressed as:

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\sqrt{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&beta;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, E _c is the amplitude of the electric field of the light wave, ω _c is the central angular frequency of the light wave, ω _plt is the angular frequency of the pilot sine wave, ω _sw is the angular frequency of the scanning sine wave, and g(t) is the downlink baseband signal 1-10 , _ma is the modulation index, and β is the phase modulation index.

The intensity modulator 1-3 is connected to the Fabry-Perot optical filter 1-4, and its impulse response is:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Where r and t are the electric field reflection coefficient and transmission coefficient of the optical filter respectively, and t ² =1-r ² , τ _fp is the delay time for the optical signal to reflect one round trip in the Fabry-Perot optical resonator.

In order to meet the power requirements of the system, before the light wave of the central station is injected into the optical fiber link 2, an erbium-doped fiber amplifier (EDFA) 1-5 with an amplification factor of A _o is used to output the Fabry-Perot optical filter 1-4 The light wave is amplified, so the final expression of the light wave electric field output by the central station is:

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>\sqrt{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">j</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&beta;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

$<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Rexp</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&beta;</span>}{\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Where R is the power reflection coefficient, R=r ² .

The receiving end of the base station 3 directly uses the photodetector 3-1 to perform photoelectric conversion on the received light wave, and the output photocurrent can be expressed as:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cos"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">cos</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Wherein i ₀ is the average photocurrent, and i ₀ =F·P ₀ , where P ₀ and F are the input optical power and responsivity of the photodetector 3-2, respectively.

Take τ _fp =0.5/f _sw , f _sw is the scanning frequency, expand the above formula with Bessel function as:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cos"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">cos</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}{\mathrm{<span\; class="notranslate">\; J</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>$

$\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="J"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">J</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>$

$\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="J"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">J</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

It can be seen from the expression (5) that the signal output by the photodetector is composed of amplitude-modulated waves with frequency components of 2nω _sw and (2n+1)ω _sw , and the selection of ω _c and τ _fp by design makes cosω _c τ _fp =1, so as to maximize the even harmonic components and eliminate the odd harmonic components (2n+1)ω _sw in the signal, so the signal is simplified as:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cos"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">cos</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; R</span>}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="J"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">J</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Where D represents a DC component, and D=1+R ² +2RJ ₀ (2β).

It can be seen from the expression (6) that the signal is composed of two AM waves, one is the AM wave whose angular frequency is 2nω _sw modulation signal is the baseband signal g(t), and the other is the angular frequency is 2nω _sw modulation signal as the guide AM wave of frequency signal cosω _plt t. From the perspective of spectrum, the signal spectrum contains the frequency components of 2nω _sw and 2nω _sw ±ω _plt . The component with a frequency of 2nω _sw is the downlink carrier carrying the baseband signal, and the component with a frequency of 2nω _sw +ω _plt or 2nω _sw -ω _plt can be extracted as the millimeter-wave reference local oscillator for uplink down-conversion. Therefore, the millimeter-wave amplification splitter 3-2 is placed behind the photodetector 3-1, and the input signal is divided into two outputs while amplifying the signal, and one path is connected to a millimeter-wave bandpass filter with a central angular frequency of 2nω _sw 3-3(1), thereby obtaining the millimeter-wave carrier carrying the baseband signal, and sending it out through the circulator three-terminal circulator 3-4 and the antenna 3-5 to realize the downlink transmission function of the signal. The expression of the millimeter wave modulated downlink signal is as follows:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; R</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cos"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">cos</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="J"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">J</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Wherein A _el is the gain of the millimeter wave amplifier splitter 3-2.

The other output of the millimeter-wave amplifier splitter 3-2 is filtered by the millimeter-wave bandpass filter 3-3(2) with a central angular frequency of 2nω _sw +ω _plt or 2nω _sw -ω _plt , and can be used as an uplink Provides millimeter-wave reference local oscillators 3-7.

The acquisition of the millimeter-wave reference local oscillator 3-7 in base station 3 is a key technology for uplink signal transmission. After solving this problem, the uplink signal transmission process becomes relatively simple:

In the base station 3, after the signal received by the antenna 3-5 passes through the three-terminal circulator 3-4 and the low noise amplifier 3-6, it is down-converted with the millimeter-wave reference local oscillator 3-7 generated above through the mixer 3-8, Take out the intermediate frequency subcarrier modulated by the uplink baseband signal, filter and amplify the intermediate frequency subcarrier with the intermediate frequency filter amplifier 3-9, so that it can directly modulate the laser 3-10; the uplink optical wave modulated by the intermediate frequency subcarrier is transmitted to the The receiving end of the central station 3; in the central station 3, through the photoelectric conversion of the photodetector 1-6, the intermediate frequency subcarrier is obtained, and then the frequency is down-converted to the baseband by the intermediate frequency mixer 1-12, and then the user is recovered by the decision device 1-13 Uplink baseband signals 1-14.

Compared with the prior art, the present invention has the following prominent features and significant advantages: (1) The sending end of the central station inserts the pilot into the baseband signal, that is, modulates the light wave intensity with the mixed signal of the pilot sine wave and the baseband signal, and uses a sweep The frequency sine wave modulates the light wave phase, and the Fabry-Perot optical filter is used to form a comb-like spectrum, so that the millimeter-wave carrier and the millimeter-wave reference local oscillator carrying the baseband signal are respectively extracted through two millimeter-wave filters with different parameters in the base station. Simplified base station equipment. (2) The method of inserting pilots in the downlink transmission link provides the required millimeter-wave reference local oscillator for down-conversion of uplink signal transmission in the base station, avoiding the use of expensive millimeter-wave local oscillator sources in the base station, and can effectively reduce the Base station overhead. (3) Both the downlink modulated wave generation and the uplink millimeter wave local oscillator generation in the base station are based on the optical frequency sweep method, which makes the base station equipment passive.

Description of drawings:

Attached picture: Schematic diagram of the two-way transmission device of the millimeter-wave ROF system with the insertion pilot method. The numbers in the figure indicate: central station 1, optical fiber bidirectional transmission link 2, base station 3, laser 1-1, phase modulator 1-2, intensity modulator 1-3, Fabry-Perot optical filter 1-4, erbium-doped Optical fiber amplifier (EDFA) 1-5, swept frequency sine wave oscillator 1-6, microwave amplifier 1-7, pilot frequency oscillator 1-8, multiplexer 1-9, downlink baseband signal 1-10, optical detector 1-11, intermediate frequency mixer 1-12, decision device 1-13, uplink baseband signal 1-14, optical detector 3-1, millimeter wave amplifier splitter 3-2, millimeter wave bandpass filter 3- 3(1), millimeter wave bandpass filter 3-3(2), three-terminal circulator 3-4, antenna 3-5, low noise amplifier 3-6, millimeter wave reference local oscillator 3-7, millimeter wave mixer frequency converter 3-8, intermediate frequency filter amplifier 3-9, laser device 3-10,

Detailed ways:

A preferred embodiment of the present invention is: the bidirectional transmission device and signal transmission method of the millimeter-wave optical fiber transmission system using the insertion pilot method is a bidirectional transmission device and signal transmission method applied to a 40GHz optical fiber transmission system. The introduction is as follows: The two-way transmission device of the millimeter-wave optical fiber transmission system is shown in the accompanying drawings, and the central station 1 and the base station 3 are interconnected through the optical fiber two-way transmission link 2 to form the uplink and downlink:

1), the structure of the downlink is: the laser 1-1 in the central station 1 is connected to a phase modulator 1-2 by a pigtail, and a frequency-sweeping sine wave oscillator 1-6 is connected to the The input end of a microwave amplifier 1-7, the output end of the microwave amplifier 1-7 is connected to the control electrode of the phase modulator 1-2 through an electric wire, and the output end of the phase modulator 1-2 is connected to the intensity modulator through a pigtail 1-3, a pilot frequency oscillator 1-8 and a downlink baseband signal 1-10 are respectively connected to two input terminals of a multiplexer 1-9 through electric wires, and the output terminals of the multiplexer 1-9 are connected through electric wires. The wire is connected to the control electrode of the intensity modulator 1-3, the output end of the intensity modulator 1-3 is connected to a Fabry-Perot optical filter 1-4 through a pigtail, and the output end of the Fabry-Perot optical filter 1-4 Connect an erbium-doped fiber amplifier EDFA1-5 through the pigtail, and the output end of the erbium-doped fiber amplifier EDFA1-5 is connected to the optical fiber bidirectional transmission link 2 through the pigtail; the end of the optical fiber bidirectional transmission link 2 is connected in the base station 3 The input end of a photodetector 3-1, the output end of the photodetector 3-1 are connected to the input end of a millimeter-wave amplification splitter 3-2 through electric wires, and one output of the millimeter-wave amplification splitter 3-2 terminal is connected to the input end of a millimeter-wave bandpass filter 3-3 (1) through an electric wire, and the output end of the millimeter-wave bandpass filter 3-3 (1) is connected to a three-terminal circulator 3-4 through an electric wire Port 1, port 2 of the three-terminal circulator 3-4 is connected to the antenna 3-5 through the feeder, and the millimeter wave signal is transmitted through the antenna 3-5, thereby realizing the downlink transmission function of the signal; the millimeter wave amplifier splitter 3-2 The other output end is connected to the input end of another millimeter wave bandpass filter 3-3(2), and the millimeter wave reference local oscillator 3-7 is obtained at the output end of the millimeter wave bandpass filter 3-3(2), Provides a down-conversion reference local oscillator for uplink signal transmission;

2), the structure of the uplink is: the user signal collected by the antenna 3-5 in the base station 3 enters the 3-4 port 2 of the three-terminal circulator through the feeder line, and the 3-4 port of the three-terminal circulator 3 output, the three-terminal circulator 3-4 port 3 is connected to the input terminal of a low noise amplifier 3-6 through an electric wire, and the output end of the low noise amplifier 3-6 is connected to one of a millimeter wave mixer 3-8 through an electric wire The input terminal, the millimeter wave reference local oscillator 3-7 output by the output terminal of the millimeter wave bandpass filter 3-3 (2) is added to the other input terminal of the millimeter wave mixer 3-8 through an electric wire, The output end of the millimeter wave mixer 3-8 is connected to the input end of an intermediate frequency filter amplifier 3-9 through an electric wire, and the output end of the intermediate frequency filter amplifier 3-9 is connected to the input end of a laser 3-10 through an electric wire. The light waves output by 3-10 are connected to the optical fiber bidirectional transmission link 2 through pigtails; The output terminal of the intermediate frequency mixer 1-12 is connected to an input terminal of the intermediate frequency mixer 1-12 through an electric wire, and the other input end of the intermediate frequency mixer 1-12 is connected to the output end of the pilot frequency oscillator 1-8 through an electric wire, and the intermediate frequency mixer The output terminal of the decision unit 1-12 is connected to the input terminal of a decision unit 1-13 through an electric wire, and the decision unit 1-13 directly outputs the user uplink baseband signal 1-14.

The two-way signal transmission method of the millimeter-wave optical fiber transmission system with the insertion pilot method is as follows:

1), Downlink signal transmission method: In the central station 1, the frequency-swept sine wave is used to phase-modulate the light wave, and the mixed signal of the downlink baseband signal and the pilot sine wave is used to modulate the intensity of the light wave, and the Fabry-Perot optical filter 1- 4. Filter the light wave with double modulation of intensity and phase to generate comb spectrum; at the base station 3, the light wave transmitted from the central station 1 undergoes photoelectric conversion through the photodetector 3-1, and then amplifies the splitter 3-2 with a millimeter wave The photoelectrically converted signal is amplified and divided into two branches, and then passed through two different millimeter wave bandpass filters 3-3(1), (2), one of which obtains the millimeter wave downlink modulated wave , the other branch obtains the millimeter-wave reference local oscillator 3-7; the branch that obtains the millimeter-wave downlink modulated wave will obtain the millimeter-wave downlink modulated wave, which is amplified and then emitted by the antenna 3-5, thereby realizing the downlink signal transmission function ; At the same time, the branch of the millimeter-wave reference local oscillator 3-7 provides the millimeter-wave reference local oscillator 3-7 for uplink signal transmission;

2), uplink signal transmission method: the user millimeter wave uplink signal received by the base station 3 from the antenna 3-5 is amplified by the low noise amplifier 3-6, and then mixed with the millimeter wave reference local oscillator in the mixer 3-8 3-7 frequency mixing, to realize the down-conversion of the signal, obtain the intermediate frequency subcarrier modulated by the uplink baseband signal, directly modulate the laser 3-10 with the intermediate frequency subcarrier, and transmit the output to the optical detector 1-11 of the central station 1, through After the photoelectric conversion, the intermediate frequency subcarrier is output, and then the uplink baseband signal 1-14 of the user is output through the down conversion and the decision device, so as to realize the uplink signal transmission function.

The signal processing process of this embodiment is as follows: at the transmitting end of the central station 1, a semiconductor laser 1-1 used as a light source operates at a wavelength of 1550 nm, a line width of 10 MHz, and a power of 10 mW. The swept sine wave oscillator 1-6 generates a swept sine wave with a frequency of f _sw =5 GHz, which is amplified by the microwave amplifier 1-7 for 30 dB, and drives the LiNbO ₃ phase modulator 1-2. The pilot frequency oscillator 1-8 produces the pilot frequency sine wave of f _plt =2 GHz and the downlink baseband signal 1-5 is mixed with a rate of 100 Mbps, and is jointly added to the control electrode of the intensity modulator 1-3, and the intensity modulator 1-3 The output is a double-modulated light wave of phase and intensity, and the light wave forms a comb spectrum after passing through a Fabry-Perot optical filter with FSR=10GHz (τ _fp =0.1ns). In order to meet the requirements of the signal transmission power in the base station, the downlink optical wave is amplified by 20 dB with erbium-doped fiber amplifier (EDFA) 1-5 before being sent to the optical fiber link 2 . The light wave electric field finally output by the central station can be expressed as:

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>\sqrt{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">j</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&beta;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

$<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Rexp</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&beta;</span>}{\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

Among them, E _c is the amplitude of the electric field of the light wave, ω _c is the central angular frequency of the light wave, ω _plt is the angular frequency of the pilot sine wave, ω _sw is the angular frequency of the scanning sine wave, and g(t) is the downlink baseband signal 1-10 , _ma is the modulation index, β is the phase modulation index, τ _fp is the delay time of the optical signal reflected in the Fabry-Perot optical resonator for a round trip, R is the power reflection coefficient of the Fabry-Perot optical filter, A _o is the doped The magnification of Erbium Fiber Amplifier (EDFA).

After the downlink light wave is photoelectrically converted by the photodetector 3-1 in the base station 3, the output photocurrent is expanded by the Bessel function as:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cos"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">cos</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}{\mathrm{<span\; class="notranslate">\; J</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>$

$\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="J"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">J</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>$

$\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="J"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">J</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

Take τ _fp =0.5/f _sw , and choose ω _c and τ _fp to make cosω _c τ _fp =1, so as to maximize the even harmonic components and eliminate the odd harmonic components in the signal (2n+1)ω _sw , this embodiment is 40GHz, so it is necessary to extract the 8th harmonic component, and the signal is simplified as:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cos"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">cos</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; R</span>}{\mathrm{<span\; class="notranslate">\; J</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

Where D represents a DC component, and D=1+R ² +2RJ ₀ (2β).

Use the millimeter wave amplifier splitter 3-2 to amplify the signal in the frequency range of 37.5GHz to 40.5GHz by 17dB and divide it into two outputs, one of which is connected to a millimeter wave bandpass filter with a center frequency of 40GHz and a 3dB bandwidth of ±200MHz 3-3(1), take out the 40GHz millimeter wave carrier carrying the baseband signal, and its expression is:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; R</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cos"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">cos</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; J</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

Wherein A _el is the gain of the millimeter wave amplifier splitter 3-2.

The signal is then sent out via the circulator 3-4 and the antenna 3-5, completing the downlink function of the signal.

The other output of the millimeter-wave amplifier splitter 3-2 is connected to a millimeter-wave bandpass filter 3-3(2) whose center frequency is 38GHz and a 3dB bandwidth of 40MHz, and the millimeter-wave reference local oscillator 3-7 of 38GHz is taken out. The expression is:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; ro</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; R</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">R</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cos"\; filenames="C2006101167010014H1.png"\; state="\{\{state\}\}">cos</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; J</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; sw</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; fp</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; plt</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

The key technology of the uplink in base station 3 is the generation of the millimeter-wave reference local oscillator 3-7. After solving this problem through the above method, the structure and signal processing process of the uplink become relatively simple:

The signal received by the antenna 3-5 of the base station 3 is a 40GHz millimeter wave signal modulated by the user's uplink baseband information. After the millimeter wave signal passes through the three-terminal circulator 3-4 and the low noise amplifier 3-6, it passes through the mixer 3- 9 and millimeter wave local oscillator 3-8 homodyne frequency conversion takes out the intermediate frequency subcarrier of 2GHz, and the intermediate frequency filter amplifier 3-9 with the amplification factor of 40dB, the center frequency of 2GHz, and the bandwidth of ±200MHz filters and amplifies the intermediate frequency subcarrier to make it Can directly modulate the laser 3-10; the uplink light wave received by the central station 3 is photoelectrically converted by the photodetector 1-6 to obtain an intermediate frequency subcarrier, and then down-converted to the baseband by the intermediate frequency mixer 1-12 and the local oscillator of 2GHz, Then use the decider 1-13 to restore the user uplink baseband signal 1-14.

Claims (2)

1. A bidirectional transmission device based on the insertion pilot method millimeter-wave optical fiber transmission system, the uplink and downlink are formed by the interconnection of the central station (1) and the base station (3) by the optical fiber bidirectional transmission link (2), and it is characterized in that : 1) The structure of the downlink is: the laser (1-1) in the central station (1) is connected with a phase modulator (1-2) by a pigtail, and a swept sine wave oscillator (1- 6) Connect to the input terminal of a microwave amplifier (1-7) by electric lead, the output end of microwave amplifier (1-7) connects the control electrode of described phase modulator (1-2) by electric lead, phase modulator The output end of (1-2) is connected to an intensity modulator (1-3) through a pigtail, and a pilot frequency oscillator (1-8) and a downlink baseband signal (1-10) are respectively connected to a combination The two input ends of the wave combiner (1-9), the output end of the wave combiner (1-9) is connected to the control electrode of the described intensity modulator (1-3) by electric wire, the intensity modulator (1-3) The output end of the Fabry-Perot optical filter (1-4) is connected with a Fabry-Perot optical filter (1-4) by a pigtail, and the output end of the Fabry-Perot optical filter (1-4) is connected with an erbium-doped fiber amplifier EDFA (1-5) by a pigtail, The output end of the erbium-doped fiber amplifier EDFA (1-5) is connected to the described optical fiber two-way transmission link (2) by a pigtail; the end of the described optical fiber two-way transmission link (2) is connected to a The input end of the light detector (3-1), the output end of the light detector (3-1) is connected to the input end of a millimeter-wave amplification splitter (3-2) by an electric lead, and the millimeter-wave amplification splitter ( One output end of 3-2) is connected to the input end of a millimeter-wave bandpass filter (3-3(1)) through an electric wire, and the output end of the millimeter-wave bandpass filter (3-3(1)) is passed through an electric wire The wire is connected to port 1 of a three-terminal circulator (3-4), and port 2 of the three-terminal circulator (3-4) is connected to the antenna (3-5) through a feeder, and the millimeter wave signal is transmitted through the antenna (3-5) , so as to realize the downlink transmission function of the signal; the other output end of the millimeter wave amplifier splitter (3-2) is connected to the input end of another millimeter wave bandpass filter (3-3(2)). The output end of the bandpass filter (3-3(2)) obtains the millimeter-wave reference local oscillator (3-7), which provides a down-conversion reference local oscillator for uplink signal transmission; 2) The structure of the uplink is: the user signal collected by the antenna (3-5) in the base station (3) enters the port 2 of the three-terminal circulator (3-4) through the feeder line, and is circulated by the three-terminal The port 3 of the three-terminal circulator (3-4) is output, and the port 3 of the three-terminal circulator (3-4) is connected to the input end of a low noise amplifier (3-6) by an electric wire, and the output end of the low noise amplifier (3-6) is passed through an electric wire. The wire is connected to an input end of a millimeter wave mixer (3-8), and the millimeter wave reference local oscillator (3-7) outputted by the output end of the millimeter wave bandpass filter (3-3(2)) Add to the other input end of the millimeter wave mixer (3-8) through electric lead, the output end of millimeter wave mixer (3-8) connects the input end of an intermediate frequency filter amplifier (3-9) through electric lead , the output end of the intermediate frequency filter amplifier (3-9) is connected to the input end of a laser (3-10) through an electric wire, and the light wave output by the laser (3-10) is connected to the optical fiber bidirectional transmission link (2) through a pigtail; In the central station (1), the input end of an optical detector (1-11) is connected to the optical fiber bidirectional transmission link (2), and the output end of the optical detector (1-11) is connected to the intermediate frequency One input end of the mixer (1-12), the other input end of the intermediate frequency mixer (1-12) is connected with the output end of the pilot frequency oscillator (1-8) by electric wire, the intermediate frequency mixer (1 The output end of -12) is connected to the input end of a decision device (1-13) through an electric wire, and the user uplink baseband signal (1-14) is directly output from the decision device (1-13). 2. A bidirectional signal transmission method based on the insertion pilot method millimeter wave optical fiber transmission system, adopting the uplink and downlink bidirectional transmission device of the millimeter wave optical fiber transmission system according to claim 1 to carry out bidirectional signal transmission, characterized in that: 1) Downlink signal transmission method: in the central station (1) carry out phase modulation to the light wave with frequency-sweeping sine wave, carry out intensity modulation to light wave with the mixed signal of downlink baseband signal and pilot frequency sine wave, and use Fabry-Perot optical filter ( 1-4) Filtering the light waves modulated by intensity and phase to generate a comb spectrum; at the base station (3), the light waves transmitted from the central station (1) are photoelectrically converted by the photodetector (3-1), and then used The millimeter-wave amplification splitter (3-2) amplifies the photoelectrically converted signal and divides it into two branches, and then lets them pass through two different millimeter-wave bandpass filters (3-3(1), (2) ), one branch obtains the millimeter-wave downlink modulated wave, and the other branch obtains the millimeter-wave reference local oscillator (3-7); the branch that obtains the millimeter-wave downlink modulated wave amplifies the millimeter-wave downlink modulated wave It is emitted by the antenna (3-5), thereby realizing the function of downlink signal transmission; at the same time, the branch that obtains the millimeter wave reference local oscillator (3-7) provides the millimeter wave reference local oscillator (3-7) for uplink signal transmission; 2) Uplink signal transmission method: the user millimeter wave uplink signal received by the base station (3) from the antenna (3-5) is amplified by the low-noise amplifier (3-6), and then combined in the mixer (3-8) with the The millimeter-wave reference local oscillator (3-7) frequency mixing described above realizes the down-conversion of the signal, and obtains the intermediate frequency subcarrier modulated by the uplink baseband signal, and directly modulates the laser (3-10) with the intermediate frequency subcarrier, and its output is transmitted to the center The optical detector (1-11) of the station (1) outputs an intermediate frequency subcarrier after photoelectric conversion, and then outputs a user uplink baseband signal (1-14) through a down-conversion and decision device, thereby realizing the uplink signal transmission function.

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