CN106896268A - A kind of frequency expansion device, the spectrum analyzer for possessing spread spectrum function - Google Patents

Abstract

The present invention relates to a kind of frequency expansion device and possess the spectrum analyzer of spread spectrum function, wherein, the spectrum analyzer for possessing spread spectrum function includes：RF front-end module, intermediate-frequency channel module, Digital IF Processing module and frequency expansion module；Wherein, frequency expansion module is connected with the input of RF front-end module, and the output end of RF front-end module is connected with the input of intermediate-frequency channel module, and the output end of intermediate-frequency channel module is connected with Digital IF Processing module；Frequency expansion module includes first switch, second switch, third switch, put-through channel, mixing passage and the 4th switch；Wherein, measured signal is input into the frequency expansion module, and when the frequency of measured signal is less than or equal to M, the 3rd switch and the common gating measured signal of the 4th switch are input into RF front-end module through put-through channel；When the frequency of measured signal is more than M, the 3rd switch and the 4th switch common gating measured signal are input into RF front-end module through being mixed passage.

Description

A frequency extension device and a spectrum analyzer with a frequency extension function

technical field

The invention relates to the technical field of spectrum analyzers, in particular to a frequency expansion device and a spectrum analyzer with a spectrum spreading function.

Background technique

A spectrum analyzer is a receiver used to perform spectrum analysis on the signal under test. It can measure the frequency, amplitude, distortion and other related parameters of unknown signals, and usually has a wide frequency and amplitude measurement range. Mainly used in base station maintenance, electronic product research and development, production and other fields. Spectrum analyzers can also be called frequency domain oscilloscopes, tracking oscilloscopes, analytical oscilloscopes, harmonic analyzers, frequency characteristic analyzers or Fourier analyzers. The main technical indicators of the spectrum analyzer include frequency range, resolution, sweep speed, sensitivity, display mode, false response, DANL, etc.

As shown in FIG. 1 , it is a schematic circuit diagram of a traditional spectrum analyzer. The input radio frequency signal undergoes multiple frequency conversions to change the higher frequency signal into a low frequency signal that can be processed by the digital intermediate frequency processing module. Because of multiple frequency mixing, it is necessary to provide multiple local oscillator signals. In this conversion process, due to the characteristics of the mixer itself, unwanted side frequencies and nonlinear spurs will be generated. In order to ensure the purity of the signal spectrum, it is necessary to use a filter to filter out unnecessary signals.

As shown in Figure 2, it is the circuit structure diagram of the improved spectrum analyzer. The frequency range of the measurable RF signal is 9kHz to 7.5GHz. The spectrum analyzer passes through the first mixer and the intermediate frequency channel module to the input measured signal introduced by the RF front-end module, and performs multiple frequency conversions to make it a low-frequency signal that can be processed by the digital intermediate frequency module, and then sends it to the digital intermediate frequency module deal with.

In the RF front-end module, the signal to be tested enters from the input port, and the SPDT switch S1 is used to gate the input to the switch S2 or gate the input to the power load. The SPDT switch S1 may have to withstand relatively large power, so often It is composed of high-power single-pole double-throw switch or relay. The single-pole double-throw switch S2 is used to select whether the signal to be tested is input to the subsequent link of the RF front-end module or the self-calibration signal is connected to the subsequent link of the RF front-end module for self-calibration. The step attenuator is an attenuator with adjustable attenuation, and has a wide attenuation range, which can continue to attenuate the input signal under test to the best mixing frequency of the first mixer A and the first mixer B level. The single pole double throw switch S3 and the single pole double throw switch S6 work together to select the signal under test to be connected to the preselection amplifier module A or the preselection amplifier module B. When the measured signal is 9kHz to 3.2GHz, the gate is connected to the preselection amplifier module A, and the filter 1 is transmitted; when the measured signal is 3.2GHz to 7.5GHz, the gate is connected to the preselection amplifier module B, and through the single Throw switches S4 and S5 cooperate with one channel of transmission from filter 2 to filter n. The preselected amplifier module is used for the measurement of small signals. When the measured signal amplitude is relatively small and close to the noise floor of the spectrum analyzer, turning on the preamplifier will reduce the noise figure of the RF front-end module link, that is, reduce the noise , so that small signals can be measured more accurately, and the measurable small signal amplitude is smaller. Filter 1 is a low-pass filter, and its function is to suppress the image frequency of the first mixer A. Filter 2 to filter n are a plurality of bandpass filters, and their function is to suppress the image frequency of the first mixer B.

The 9kHz to 3.2GHz and 3.2GHz to 7.5GHz output by the RF front-end module are respectively mixed with the corresponding local oscillator by the first mixer A and the first mixer B to generate the first intermediate frequency signal A or the first intermediate frequency signal B, The two first intermediate frequency signals are combined into one through the single-pole double-throw switch S6 and input to the second mixer.

The existing scheme adopts the traditional superheterodyne receiving scheme, which converts the measured signal from the radio frequency signal into a digitally processable low-frequency signal through multiple frequency conversions. This scheme requires that the difference between the maximum frequency and the minimum frequency of the first local oscillator frequency must be equal to the maximum frequency and minimum frequency difference of the RF signal that can be measured by the spectrum analyzer. The wider the frequency of the measurable signal, the wider the coverage of the first local oscillator is required. The circuit The greater the difficulty and complexity of implementation. In order to reduce the difficulty of implementing the first local oscillator, the RF front-end and the first mixer are divided into two channels according to the frequency range of the signal to be tested, and the difference between the maximum frequency and the minimum frequency of the first local oscillator is about 3.2GHz, and By selecting an appropriate frequency of the first intermediate frequency signal, the first local oscillator frequency of the two channels can be basically consistent, which can be realized by using the same local oscillator generating circuit. However, if the measurable frequency is increased to above 7.5 GHz, the frequency coverage of the first local oscillator is also required to be widened, and it becomes more difficult to realize the first local oscillator.

Contents of the invention

In order to solve the problems in the prior art, the present invention proposes a frequency extension device and a spectrum analyzer with a spread spectrum function. The spectrum analyzer adds a spread spectrum module on the basis of the existing spectrum analyzer, so that without adding the first On the basis of the difficulty in realizing the local oscillator frequency, the measurable frequency range of the spectrum analyzer is expanded.

In order to achieve the above object, the present invention provides a spectrum analyzer with spread spectrum function, comprising: a radio frequency front-end module, an intermediate frequency channel module, a digital intermediate frequency processing module and a frequency extension module;

The frequency extension module is connected to the input end of the radio frequency front-end module, the output end of the radio frequency front-end module is connected to the input end of the intermediate frequency channel module, and the output end of the intermediate frequency channel module is connected to the digital intermediate frequency processing module connected;

The frequency extension module includes a first switch, a second switch, a third switch, a through channel, a frequency mixing channel and a fourth switch; wherein the measured signal is input to the frequency extension module, when the frequency of the measured signal is less than When it is equal to the frequency value M, the third switch and the fourth switch jointly select the measured signal to be input to the RF front-end module through the through channel; when the frequency of the measured signal is greater than the frequency value M, the third switch and the fourth switch The fourth switch collectively selects the signal under test to be input to the radio frequency front-end module through the frequency mixing channel.

Preferably, the input terminal of the first switch inputs the signal to be tested, the first output terminal of the first switch is connected to the first input terminal of the second switch, and the second output terminal of the first switch is connected to the One end of the power load is connected, and the other end of the power load is directly grounded; the output end of the second switch is connected to the input end of the third switch, and the second input end of the second switch is connected to the self-calibration The signal input terminal is connected; the first output terminal of the third switch is connected with the input terminal of the direct channel, the second output terminal of the third switch is connected with the input terminal of the mixing channel, and the direct channel The output end of the said fourth switch is connected to the first input end of said fourth switch, the output end of said mixing channel is connected to the second input end of said fourth switch; the output end of said fourth switch is connected to said radio frequency front end connected to the input of the module.

Preferably, the frequency mixing channel includes: a step attenuator, a preselection amplifier, a first filter unit, a mixer and a second filter unit; wherein,

The input end of the step attenuator is used as the input end of the mixing channel, and is connected to the second output end of the third switch, and the step attenuator, preselection amplifier, first filter unit, mixer connected in series with the second filtering unit in sequence, and the output end of the second filtering unit is used as the output end of the mixing channel and connected to the second input end of the fourth switch.

Preferably, the first filtering unit is a filter or a filter bank, which is used to filter out the image frequency of the mixer.

Preferably, the second filtering unit is configured to filter the signal output by the mixer, and limit the frequency of the signal output by the mixer to be less than a frequency value M .

Preferably, the local oscillator frequency of the mixer is a fixed frequency.

Preferably, the frequency value M is 7.5 GHz.

Correspondingly, in order to achieve the above object, the present invention also provides a frequency extension device for frequency extension of a spectrum analyzer, the frequency extension device includes:

The first switch, the second switch, the third switch, the direct channel, the mixing channel and the fourth switch; wherein, the input terminal of the first switch inputs the signal to be tested, and the first output terminal of the first switch is connected to the The first input end of the second switch is connected, the second output end of the first switch is connected to one end of the power load, and the other end of the power load is directly grounded; the output end of the second switch is connected to the The input end of the third switch is connected, the second input end of the second switch is connected with the self-calibration signal input end; the first output end of the third switch is connected with the input end of the through channel, the first The second output end of the three switches is connected to the input end of the mixing channel, the output end of the through channel is connected to the first input end of the fourth switch, and the output end of the mixing channel is connected to the first input end of the fourth switch. The second input ends of the four switches are connected; the output end of the fourth switch is connected with the input end of the radio frequency front-end module.

The above technical scheme has the following beneficial effects:

The technical solution is to add an external frequency extension module to the existing spectrum analyzer to extend the frequency test range of the spectrum analyzer from 7.5GHz to 13.6GHz. The frequency extension does not need to change the existing spectrum analyzer circuit, only needs to add the frequency extension module in the way of providing options to realize the frequency extension. The options can be convenient and flexible to meet the needs of different users for the frequency measurable range.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the circuit principle diagram of traditional spectrum analyzer;

Fig. 2 is the circuit structure diagram of the improved spectrum analyzer;

Fig. 3 is a kind of spectrum analyzer schematic diagram with spread spectrum function that the present invention proposes;

Fig. 4 is a kind of spectrum analyzer circuit diagram that possesses spread spectrum function that the present invention proposes;

Fig. 5 is the circuit diagram of the spectrum analyzer with spread spectrum function of the present embodiment;

Fig. 6 is a circuit diagram of a frequency extension device proposed by the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in FIG. 3 , it is a circuit diagram of a spectrum analyzer with spread spectrum function proposed by the present invention. Including: RF front-end module 301, intermediate frequency channel module 302, digital intermediate frequency processing module 303 and frequency extension module 304;

The frequency extension module is connected to the input end of the radio frequency front-end module, the output end of the radio frequency front-end module is connected to the input end of the intermediate frequency channel module, and the output end of the intermediate frequency channel module is connected to the digital intermediate frequency processing module connected.

As shown in FIG. 4 , it is a circuit diagram of a spectrum analyzer with spread spectrum function proposed by the present invention. The frequency extension module includes a first switch S7, a second switch S8, a third switch S9, a through channel, a mixing channel and a fourth switch S10; wherein, the measured signal is input to the frequency extension module, when the measured signal When the frequency of the signal is less than or equal to M, the third switch S9 and the fourth switch S10 jointly select the signal under test to be input to the RF front-end module through the through channel; when the frequency of the signal under test is greater than M, the third switch S9 The switch S9 and the fourth switch S10 jointly select the signal under test to be input to the radio frequency front-end module through the frequency mixing channel. Wherein, the input end of the first switch S7 inputs the signal to be tested, the first output end of the first switch S7 is connected to the first input end of the second switch S8, and the second end of the first switch S7 The output end is connected to one end of the power load, and the other end of the power load is directly grounded; the output end of the second switch S8 is connected to the input end of the third switch S9, and the first end of the second switch S8 The two input ends are connected to the self-calibration signal input end; the first output end of the third switch S9 is connected to the input end of the direct channel, and the second output end of the third switch S9 is connected to the mixing channel. The input end is connected, the output end of the direct channel is connected to the first input end of the fourth switch S10, the output end of the mixing channel is connected to the second input end of the fourth switch S10; the first input end of the fourth switch S10 is connected; The output terminals of the four switches S10 are connected to the input terminals of the radio frequency front-end module.

For this embodiment, the frequency value M is 7.5 GHz, and after spectrum spreading, the highest frequency of the spectrum analyzer test signal is 13.6 GHz. It should be noted that the above application scenarios are only shown for the purpose of understanding the spirit and principle of the present invention, and the implementation manners of the present invention are not limited in this respect. On the contrary, the embodiments of the present invention can be applied to any applicable scene.

As shown in FIG. 5 , it is a circuit diagram of a spectrum analyzer with spread spectrum function in this embodiment. When the spectrum analyzer tests the highest frequency is 7.5GHz, the signal to be tested is input into the spectrum analyzer 1 from the radio frequency input port 1 for testing.

When the test frequency of the spectrum analyzer is extended to 13.6 GHz, spectrum spread is realized by adding a frequency extension module on the basis of the spectrum analyzer 1. At this time, the measured signal is input from the RF input port 2 and transmitted to the spectrum analyzer through the frequency extension module. 1 for testing. In the frequency extension module, the signal to be tested enters from the input port, and the SPDT switch S7 is used to gate the input to the SPDT switch S8 or the gate input to the power load. The SPDT switch S7 may have to withstand relatively large power. Therefore, high-power single-pole double-throw switches or relays are often used to form. The single-pole double-throw switch S8 is used to select whether the signal to be tested is input to the subsequent link of the frequency extension module or the self-calibration signal is connected to the subsequent link of the frequency extension module for self-calibration. The single pole double throw switch S9 and the single pole double throw switch S10 jointly select the transmission channel of the signal under test. When the frequency to be tested is less than 7.5GHz, the SPDT switch S9 and the SPDT switch S10 jointly select the measured signal to pass through the through channel and input it to the spectrum analyzer 1. The SPDT switch S1 and the SPDT switch in the spectrum analyzer 1 The throw switch S2 is set to gate the subsequent link, and the other control states of the spectrum analyzer 1 are the same as when no frequency extension module is added. When the measured frequency is 7.5 GHz to 13.6 GHz, the single pole double throw switch S9 and the single pole double throw switch S10 jointly select the measured signal to pass through the mixing channel and input it to the spectrum analyzer 1 . Specifically, the signal to be tested is input to the step attenuator 2 through the single-pole double-throw switch S9. The step attenuator 2 is an attenuator with adjustable attenuation and has a wide attenuation range. The output of the device 2 passes through the preselection amplifier module C and the filter input mixer, and mixes with the fixed frequency local oscillator F1. After the output of the mixer is filtered, it becomes a broadband signal with a frequency less than 7.5 GHz, and is input to the spectrum analyzer 1 through the single-pole double-throw switch S10. In the spectrum analyzer 1, the single-pole double-throw switch S1 and the single-pole double-throw switch S2 are both set In order to gate the subsequent link, the step attenuator 2 is set to not attenuate, and other control states of the spectrum analyzer 1 need to be changed accordingly. The step attenuator 2 can attenuate the input signal under test to the optimum mixing level of the first mixer A and the first mixer B. The preselection amplifier module C is used for the measurement of small signals. When the measured signal amplitude from 7.5GHz to 13.6GHz is relatively small and close to the noise floor of the spectrum analyzer, turn on the preselection amplifier, which will reduce the frequency extension module and RF front-end module. The noise figure of the link, that is, the noise is reduced, so that small signals can be measured more accurately, and the measurable small signal amplitude is smaller. The filter before the mixer in the frequency extension module may be a filter bank, which is used to filter out the image frequency of the mixer.

Spectrum analyzer spread spectrum to 13.6GHz, the working principle when the measured frequency is 7.5GHz to 13.6GHz, more detailed examples are:

If the signal to be tested is 7.5GHz to 13.6GHz, the signal to be tested is input to the frequency mixing channel through the SPDT switch S7, SPDT switch S8, and SPDT switch S9, and then mixed with the local oscillator F1 and output to the frequency spectrum analyzer1. If the frequency of the local oscillator F1 is 7GHz, the output of the mixing channel is 500MHz to 6.6GHz, and the spectrum analyzer 1 can be regarded as a signal test from 500MHz to 6.6GHz, and each control state of the spectrum analyzer 1 is correspondingly called 500MHz to 6.6 The corresponding state at GHz. In this way, when testing 7.5GHz to 13.6GHz, by adding a first-stage mixing method, the frequency conversion of the signal under test to the RF signal that can be tested by the spectrum analyzer 1 is performed, and the frequency is converted three times by the spectrum analyzer 1 to the digital intermediate frequency processing module. The signal that can be processed can realize the measurement of the measured signal at a frequency of 7.5GHz to 13.6GHz. Compared with the non-spreading state, the spectrum analyzer 1 only needs to change the control status of each switch according to the frequency output by the frequency expansion module. There is no need to modify the circuit of the spectrum analyzer 1, and the implementation is simple.

A further example is the spectrum analyzer after frequency expansion, when the measured frequency 10GHz is introduced from the RF input port 2, it enters the mixing channel through the SPDT switch S7, the SPDT switch S8, and the SPDT switch S9. , after the mixing channel and the 7GHz local oscillator F1 are mixed and filtered, the output 3GHz frequency signal is gated by the single-pole double-throw switch S10 and input to the spectrum analyzer 1 from the RF input port 1. At this time, the spectrum analyzer 1 can be regarded as the test It is a 3GHz signal, and the control modules in the spectrum analyzer 1 are set according to the settings when testing the 3GHz signal, so that the spectrum analyzer can measure the measured 10GHz signal.

As shown in FIG. 6 , it is a circuit diagram of a frequency extension device proposed by the present invention. For the frequency extension of the spectrum analyzer, the frequency extension device includes:

The first switch S7, the second switch S8, the third switch S9, the through channel, the mixing channel and the fourth switch S10; wherein, the input terminal of the first switch S7 inputs the signal to be tested, and the input terminal of the first switch S7 The first output end is connected to the first input end of the second switch S8, the second output end of the first switch S7 is connected to one end of the power load, and the other end of the power load is directly grounded; The output end of the second switch S8 is connected to the input end of the third switch S9, and the second input end of the second switch S8 is connected to the self-calibration signal input end; the first output end of the third switch S9 is connected to the input end of the third switch S9. The input end of the direct channel is connected, the second output end of the third switch S9 is connected to the input end of the mixing channel, the output end of the direct channel is connected to the first input end of the fourth switch S10 The output end of the mixing channel is connected to the second input end of the fourth switch S10; the output end of the fourth switch S10 is connected to the input end of the radio frequency front-end module.

The frequency extension involved in the technical solution does not need to change the circuit of the existing spectrum analyzer, and only needs to add a frequency extension module by providing options to realize the frequency extension. The options can be convenient and flexible to meet the needs of different users for the frequency measurable range.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (8)

1. A spectrum analyzer with spread spectrum function, comprising: the system comprises a radio frequency front end module, an intermediate frequency channel module and a digital intermediate frequency processing module; it is characterized by also comprising: a frequency spreading module;

the frequency expansion module is connected with the input end of the radio frequency front-end module, the output end of the radio frequency front-end module is connected with the input end of the intermediate frequency channel module, and the output end of the intermediate frequency channel module is connected with the digital intermediate frequency processing module;

the frequency extension module comprises a first switch, a second switch, a third switch, a through channel, a mixing channel and a fourth switch; when the frequency of the signal to be tested is less than or equal to a frequency value M, the third switch and the fourth switch jointly gate the signal to be tested and input the signal to the radio frequency front end module through the through channel; and when the frequency of the detected signal is greater than the frequency value M, the third switch and the fourth switch jointly gate the detected signal to be input to the radio frequency front-end module through the frequency mixing channel.

2. The spectrum analyzer as claimed in claim 1, wherein the input terminal of the first switch inputs the signal under test, the first output terminal of the first switch is connected to the first input terminal of the second switch, the second output terminal of the first switch is connected to one terminal of the power load, and the other terminal of the power load is directly connected to ground; the output end of the second switch is connected with the input end of the third switch, and the second input end of the second switch is connected with the self-calibration signal input end; a first output end of the third switch is connected with an input end of the through channel, a second output end of the third switch is connected with an input end of the mixing channel, an output end of the through channel is connected with a first input end of the fourth switch, and an output end of the mixing channel is connected with a second input end of the fourth switch; and the output end of the fourth switch is connected with the input end of the radio frequency front-end module.

3. The spectrum analyzer of claim 2, wherein the mixing channel comprises: the device comprises a step attenuator, a pre-selection amplifier, a first filtering unit, a mixer and a second filtering unit; wherein,

the input end of the step attenuator is used as the input end of the frequency mixing channel and is connected with the second output end of the third switch, the step attenuator, the pre-selection amplifier, the first filtering unit, the frequency mixer and the second filtering unit are sequentially connected in series, and the output end of the second filtering unit is used as the output end of the frequency mixing channel and is connected with the second input end of the fourth switch.

4. The spectrum analyzer as claimed in claim 3, wherein the first filtering unit is a filter or a filter bank for filtering an image frequency of the mixer.

5. The spectrum analyzer of claim 3, wherein the second filtering unit is configured to filter the signal output by the mixer to limit the frequency of the signal output by the mixer to less than a frequency value M.

6. The spectrum analyzer of claim 3, wherein the local oscillator frequency of the mixer is a fixed frequency.

7. The spectrum analyzer as claimed in any of claims 1 to 6, wherein the frequency value M is 7.5 GHz.

8. A frequency spreading apparatus for frequency spreading of a spectrum analyzer, the frequency spreading apparatus comprising:

the first switch, the second switch, the third switch, the through channel, the mixing channel and the fourth switch; the input end of the first switch inputs a signal to be tested, the first output end of the first switch is connected with the first input end of the second switch, the second output end of the first switch is connected with one end of the power load, and the other end of the power load is directly grounded; the output end of the second switch is connected with the input end of the third switch, and the second input end of the second switch is connected with the self-calibration signal input end; a first output end of the third switch is connected with an input end of the through channel, a second output end of the third switch is connected with an input end of the mixing channel, an output end of the through channel is connected with a first input end of the fourth switch, and an output end of the mixing channel is connected with a second input end of the fourth switch; and the output end of the fourth switch is connected with the input end of the radio frequency front-end module.