JPH07221808A - Transmission system having carrier component suppression function - Google Patents

Abstract

PURPOSE:To automatically eliminate an undesired carrier component and to eliminate the need for re-adjustment by detecting a carrier component in a transmission output signal and controlling a spectral level of the carrier component based thereon. CONSTITUTION:A detector 6 receiving a transmission output signal detects a carrier component in the transmission output signal based on a carrier signal from a local oscillator 4. The detection output from the detector 6 is fed to an amplitude phase controller 7 receiving the carrier signal outputted from the local oscillator 4. The amplitude phase controller 7 changes the amplitude and phase of the carrier signal depending on the detected output. The carrier signal whose amplitude and phase is controlled by the amplitude phase controller 7 is fed to an adder 8 provided between a mixer 3 and a power amplifier 5. The adder 8 adds a base signal subjected to frequency conversion by the mixer 3 to the carrier signal whose amplitude and phase have already been controlled and gives the sum output to a power amplifier 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital radio communication device, and more particularly to a transmission system for frequency-converting and transmitting a baseband signal based on a predetermined carrier signal.

[0002]

2. Description of the Related Art FIG. 1 is a schematic block diagram showing an example of a typical transmission system in such communication equipment. In FIG. 1, an information source 1 generates, for example, an audio signal or various kinds of data as an information signal to be transmitted and supplies it to a base signal generator 2. The base signal generator 2 converts or modulates the supplied information signal into a waveform defined by the communication system to obtain a so-called base band signal (hereinafter simply referred to as a base signal), which is supplied to the mixer 3. Supply. The mixer 3 receives the supplied base signal and the predetermined frequency f emitted from the local oscillator 4.
The carrier wave signal of c is mixed, and the base signal is subjected to frequency conversion for the predetermined frequency. The base signal frequency-converted by the mixer 3 is supplied to the power amplifier 5, amplified to required power, and supplied to an antenna radiation system (not shown) as a transmission output signal.

When this transmission system is assembled with actual hardware, carrier components may be mixed into the transmission output signal in excess of the design value due to the performance and characteristic errors of the components used. is there. This is a kind of leakage phenomenon called field through. Analyzing the cause,
The following two are mainly considered. Cause 1: The isolation between the carrier signal input terminal 3L and the signal input terminal 3R in the mixer 3 is insufficient.

Cause 2: The direct current level of the base signal output from the base signal generator 2 has a deviation in design value. Particularly, in a communication system that does not transmit a carrier wave, if the carrier wave is mixed in the transmission output signal, it becomes difficult to accurately demodulate in the receiving system, and it is represented by a bit error rate (BER) or a signal-to-noise ratio (S / N). Communication quality deteriorates. further,
Even if the amount of carrier components mixed is the same, the adverse effect increases as the amount of information transmission per unit frequency increases. Therefore, it is desired to reduce the amount mixed in order to increase the transmission capacity in the future. .

FIG. 2 shows an example of the spectrum of the transmission output signal when the carrier component is not mixed in the communication system which does not transmit the carrier wave, and FIG. 3 shows an example of the spectrum of the transmission output signal when the carrier component is mixed. As can be seen from these figures, when the carrier wave component is mixed, unlike FIG.
For example, a protruding carrier signal component, that is, a carrier leakage component, which is significantly shown in FIG.

In order to avoid such inconvenience, conventionally, the following measures have been taken for the causes 1 and 2 respectively. Countermeasure 1: Select and use a mixer with good isolation characteristics. Countermeasure 2: Manually adjust the DC level of the base signal. However, the above measure 1 is not always available with a mixer having the required characteristics, and the measure 2 is complicated because it requires re-adjustment due to changes in temperature and aging.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to eliminate unnecessary signals mixed in a transmission output signal without damaging a signal to be transmitted. It is an object of the present invention to provide a transmission system that automatically removes only the carrier component and that functions by following the environment such as temperature and does not require readjustment.

[0008]

A transmission system according to the present invention is a transmission system which frequency-converts a baseband signal based on a carrier signal of a predetermined frequency to generate a transmission output signal, wherein The present invention is characterized by including detection means for detecting a carrier component and control means for controlling the spectrum level of the carrier component in the transmission output signal based on the detection output of the detection means.

[0009]

According to the transmission system having the carrier component suppressing function of the present invention, the carrier component in the transmission output signal is detected, and the spectrum level of the carrier component in the transmission output signal is controlled based on the detected output. , B in the receiving system
It is possible to avoid deterioration of ER and S / N.

[0010]

The present invention will be described in detail below with reference to the drawings. FIG. 4 is a block diagram of a main part of a transmission system according to an embodiment of the present invention, and the same parts as those in FIG. 1 are designated by the same reference numerals. In FIG. 4, the detector 6 that receives the transmission output signal detects the carrier component in the transmission output signal based on the carrier signal from the local oscillator 4. The detection output of the detector 6 is supplied to the amplitude / phase controller 7 having the output carrier signal of the local oscillator 4 as an input. The amplitude / phase controller 7 plays the roles of a variable attenuator and a variable phase shifter, and changes the amplitude and phase of the carrier signal according to the detection output. The carrier signal whose amplitude and phase are controlled by the amplitude / phase controller 7 is supplied to the mixer 3 and the power amplifier 5.
It is supplied to the adder 8 provided between and. Adder 8
Adds the base signal whose frequency has been converted by the mixer 3 and the carrier signal whose amplitude and phase have been controlled, and supplies the addition output to the power amplifier 5. In this embodiment, such a configuration is newly added to the conventional example shown in FIG.

Next, the operation of this transmission system will be described.
The transmission output signal includes a signal to be transmitted and an unnecessary carrier component. However, by calculating the correlation coefficient with the carrier signal from the local oscillator 4 in the detector 6, the transmission output signal The level and phase of the carrier component of is detected. This is because the carrier signal from the local oscillator 4 and the signal to be transmitted in the transmission output signal are uncorrelated with each other, and the carrier signal from the local oscillator 4 and the carrier component in the transmission output signal are correlated with each other. is there.

In the amplitude / phase controller 7, the local oscillator 4 is applied to the detected carrier component based on the level and phase of the carrier component in the transmission output signal obtained by the detector 6.
The carrier signal from is controlled in the adder 8 so that it has the same amplitude and the opposite phase. As a result, the carrier component is canceled in the adder 8 and does not appear in the transmission output signal.

Since these operations are performed by feedback control, the carrier component is automatically canceled and
Even if the carrier component in the transmission output signal changes due to temperature, change with time, failure, etc., it automatically follows and is held constant, so that readjustment is unnecessary. Thus, in this embodiment, a good spectrum in the transmission output signal as shown in FIG. 2 can be obtained.

The detector 6 and the amplitude / phase controller 7 in the transmission system of FIG. 4 are configured to separate the quadrature component and the in-phase component and perform detection and amplitude / phase control for each component as shown in FIG. 5, for example. can do. In FIG. 5, the detector 6
Is a quadrature distributor 11 that receives a carrier signal as an input and separates and outputs the carrier signal into an in-phase component and a quadrature component, an in-phase distributor 12 that receives a transmission output signal as an input, and distributes and outputs this in-phase component, and a quadrature distributor 11 A multiplier 13A that multiplies the in-phase component and the signal from the in-phase distributor 12, a multiplier 13B that multiplies the quadrature component from the quadrature distributor 11 and the signal from the in-phase distributor 12, and the multiplication output of the multiplier 13A. Low pass filter (LPF) that passes the specified low frequency band of
14A and a low-pass filter 14B that passes a predetermined low frequency band of the multiplication output of the multiplier 13B.

The amplitude / phase controller 7 receives a carrier wave signal as an input and separates and outputs the carrier wave signal into an in-phase component and a quadrature component, an in-phase component from the distributor 11P and an output of the LPF 14A in the detector 6. And a multiplier 9B for multiplying the quadrature component from the distributor 11P and the output of the LPF 14B in the detector 6,
It is composed of an adder 10 that adds the multiplication output of the multiplier 9A and the multiplication output of the multiplier 9B and outputs an addition input signal to the adder 8.

The operation of this configuration is generally known as an adaptive canceller. To briefly explain this, as an example, the carrier wave signal (1) from the local oscillator 4 is used.
It is assumed that a leakage component (2) (1/3) cos (ωt−30 °) whose amplitude is delayed by 1/3 and phase is delayed by 30 ° with respect to cosωt is mixed in the transmission output signal. At this time, for simplification of description, it is assumed that the terminal of the signal (3) is disconnected in the adder 8 which adds the signal (3) for cancellation. Although the base signal modulated by the mixer 3 is included in the transmission output signal, it is ignored because it does not affect the operation of the adaptive canceller (because (6) ′).
′, (7) ″ because these components become zero).

In the detector 6, the carrier signal (1) cosωt from the local oscillator 4 is supplied to the in-phase component (6) cosωt and the quadrature component (7) cos (ωt-90 °), that is, sinω.
divided into t, the feedback signal (8) (1 /) of the leakage component (2)
3) Calculate the product with cos (ωt-30 °). These results are

[0018]

## EQU1 ## (6) '= (6) × (8) = cosωt × (1/3) cos (ωt-30 °) = (1/6) {cos (2ωt-30 °) + cos30 °} (7 ) ′ = (7) × (8) = sin ωt × (1/3) cos (ωt−30 °) = (1/6) {sin (2ωt−30 °) + sin30 °}. The LPFs 14A and 14B block the second-harmonic component 2ωt of the carrier wave and output only the direct-current component. In the end, the correlation between (6) and (8) and (7) and (8) is calculated. Become. LPF pass band gain-
If set to 2 (in many cases an inverting amplifier is actually needed), these outputs are (6) ″ (− 1 /
3) cos 30 ° and (7) ″ (-1/3) sin3
It becomes 0 ° and is input to the multipliers 9A and 9B of the amplitude / phase controller 7. In the amplitude / phase controller 7, the carrier wave signal (1) cosωt from the local oscillator 4 is converted into the in-phase component (4) cosω by a method of changing the amplitude / phase by so-called rectangular coordinates.
The amplitude and phase are changed separately for t and the orthogonal component (5) sinωt. The amount of change of each component is the LPF output signal (6)
'' (-1/3) cos 30 ° and (7) '' (-1 /
3) Since it is set to sin 30 °, the results are

[0019]

## EQU00002 ## (4) '= (4) * (6)' '= (-1/3) cos30 DEG cosωt (5)' = (5) * (7) '' = (-1/3) sin30 The signal (3), which is ゜ sinωt

[0020]

## EQU00003 ## (3) = (4) '+ (5)' = (-1/3) cos30 DEG cosωt-1 / 3 sin30 DEG sinωt = (-1/3) cos (ωt-30 DEG) = (1 / 3) cos (ωt−150 °) = − (2), the leak signal (2) to be canceled
With just the same amplitude and opposite phase. Now adder 8 (3)
If they are connected and the two signals (2) and (3) are added together, they will cancel and will not appear in the transmission output. In this way, the detector 6 automatically detects the amplitude and phase of the leakage signal, and the amplitude / phase controller 7 generates a signal of the same amplitude and opposite phase.

The above situation is expressed by using a vector as shown in FIG. Since the signal end of (3) is actually connected to the adder 8 from the beginning, the feedback signal (8) is not necessarily the same as the leakage signal (2), but the signal (3) for canceling is used. ), It converges to the optimum value continuously. On the other hand, this behavior is described in the paper “B. Widrow, JR Glover, Jr., JM Mc.
Cool "Adaptive Noise Cancelling: Principles and Ap
replications "Proceedings of the IEEE, Vol.63, No.12,
December 1975, pp.1692 ”also shows detailed principles, operations, and application examples.

The configuration for removing the leakage component is shown in FIG.
In addition to the configuration in which a desired signal is obtained by dividing the in-phase component and the quadrature component and changing the amplitudes of each in-phase component and quadrature component as shown in FIG. You can also In FIG. 7, the output carrier signal of the local oscillator 4 is supplied to the adder 8 via the variable attenuator 21 and the variable phase shifter 22. The detector / controller 23 detects the carrier leakage component in the transmission output signal, and in response thereto, the attenuation amount of the variable attenuator 21 and the variable phase shifter 22 to generate the leakage component removal signal to be supplied to the adder 8. And change the amount of phase shift. As a result, the same effect as that of FIG. 5 can be obtained. It goes without saying that the variable attenuator 21 may be replaced with a variable gain amplifier, and the variable phase shifter 22 may be replaced with a delay circuit. Also,
What can be said by comparing the configuration of FIG. 7 with the configuration of FIG.
The hardware of the configuration of FIG. 5 is easier to implement.

Further, in order to eliminate only the cause 2 described in the section of the prior art, the configuration as shown in FIG. 8 can be adopted. FIG. 8 is a block diagram of a main part of a transmission system showing a second embodiment of the present invention. In FIG. 8, the detector 1
7 detects a carrier component in the transmission output signal and supplies the detected output to the DC generator 15. The DC generator 15 is
An adder 1 provided between the base signal generator 2 and the mixer 3 generates a DC signal corresponding to a deviation of the DC level of the base signal from a required value (predetermined reference value) based on the detection output.
Supply to 6. The adder 16 adds the supplied DC signal to the output of the base signal generator 2 so that the DC level of the base signal is corrected to the required value.

The baseband signal in each of the above embodiments is not limited to a specific modulation method. Various modulation methods such as quadrature modulation, ASK and FSK can be adopted.

[0025]

As described in detail above, according to the transmission system having the carrier component suppressing function of the present invention, the carrier component in the transmission output signal is detected, and the carrier in the transmission output signal is detected based on the detected output. Since the spectrum level of the component is controlled and the spectrum of the transmission output signal is shaped,
It automatically removes only unnecessary carrier components mixed in the transmission output signal without damaging the signal to be transmitted, and also functions by following the environment such as temperature and does not require readjustment to properly detect carrier components. Can be suppressed. In particular, the present invention is extremely effective in increasing the transmission capacity in a communication system.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an example of a typical transmission system in a communication device.

FIG. 2 is a spectrum diagram of a transmission output signal that does not include unnecessary carrier components.

FIG. 3 is a spectrum diagram of a transmission output signal including an unnecessary carrier component.

FIG. 4 is a block diagram of a main part of a transmission system according to an embodiment of the present invention.

5 is a block diagram showing an example of a specific configuration of a detector 6 and an amplitude / phase controller 7 in the transmission system of FIG.

FIG. 6 is a vector diagram showing the operation of the configuration of FIG.

7 is a block diagram showing another example of a specific configuration of a detector 6 and an amplitude / phase controller 7 in the transmission system of FIG.

FIG. 8 is a block diagram of a main part of a transmission system showing a second embodiment of the present invention.

[Explanation of symbols]

 1 Information Source 2 Base Signal Generator 3 Mixer 4 Local Oscillator 5 Power Amplifier 6 Detector 7 Amplitude / Phase Controller 8 Adder 9A, 9B Multiplier 10 Adder 11, 11P Quadrature Distributor 12 In-phase Distributor 13A, 13B Multiply Device 14A, 14B Low-pass filter 15 DC generator 16 Adder 17 Detector 21 Variable attenuator 22 Variable phase shifter 23 Detection / control device

Front Page Continuation (72) Inventor Ryuichi Masuda 3-20-1 Minamiazabu, Minato-ku, Tokyo Inside Nippon Motorola Co., Ltd.

Claims (6)

[Claims] 1. A transmission system that frequency-converts a baseband signal based on a carrier signal of a predetermined frequency to generate a transmission output signal, the detecting means detecting a carrier component in the transmission output signal, and the detection. And a control means for controlling the spectrum level of the carrier component in the transmission output signal based on the detection output of the means. 2. A transmission having frequency conversion means for frequency-converting a baseband signal based on a carrier signal of a predetermined frequency, and transmission output signal generation means for generating a transmission output signal according to the conversion output of the frequency conversion means. In the system, a detection unit that detects a carrier component in the transmission output signal, and a control unit that controls the spectrum level of the carrier component in the converted output of the frequency conversion unit based on the detection output of the detection unit. A transmission system having a carrier wave component suppressing function. 3. The detector according to claim 1, wherein the detector detects the carrier component by calculating the degree of correlation between the carrier signal and the carrier component in the transmission output signal. Transmission system. 4. The removing means for generating a carrier wave removing signal of equal amplitude and opposite phase to the carrier wave component detected by the detecting means based on the carrier wave signal, and the frequency converting means. 3. The transmission system according to claim 2, further comprising: a removal signal adding unit that adds the carrier wave removal signal to the converted output of. 5. A transmission having frequency conversion means for frequency-converting a baseband signal based on a carrier signal of a predetermined frequency, and transmission output signal generation means for generating a transmission output signal according to the conversion output of the frequency conversion means. A system comprising: detection means for detecting a carrier component in the transmission output signal; and DC level control means for controlling the DC level of the baseband signal based on the detection output of the detection means. A transmission system having a function of suppressing a carrier wave component. 6. The direct current level control means generates a direct current signal corresponding to a deviation of a direct current level of the base band signal from a predetermined reference value based on the carrier component detected by the detection means. 6. The transmission system according to claim 5, further comprising: a DC addition unit that adds the DC signal to the baseband signal.