CN112068105B - System and method for analyzing signal spectrum of frequency modulation continuous wave laser radar receiver - Google Patents
System and method for analyzing signal spectrum of frequency modulation continuous wave laser radar receiver Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4816—Constructional features, e.g. arrangements of optical elements of receivers alone
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a signal spectrum analysis system of a frequency modulation continuous wave laser radar receiver, which carries out filtering and gain on a received current analog electric signal, carries out coarse frequency discrimination on the current analog electric signal after the filtering and gain to obtain an estimated current analog electric signal frequency, selects a local oscillation frequency needing to be mixed, carries out mixing on the current analog electric signal after the filtering and gain and the local oscillation frequency to obtain a low-frequency analog electric signal, carries out Fourier transformation and analysis processing on the low-frequency analog electric signal after the low-pass filtering processing, and can greatly reduce the performance requirements of an analog-digital converter and an FPGA.
Description
Technical Field
The invention relates to the technical field of laser ranging, in particular to a frequency modulation continuous wave laser radar receiver signal spectrum analysis system and method.
Background
The frequency modulation continuous wave laser ranging can realize high-precision ranging measurement, and is widely focused and applied in the fields of radars and lidars. Compared with the traditional time-of-flight ranging, the frequency modulation continuous wave has the advantages of interference resistance in coherent detection, no need of instantaneous high power, no need of a high-speed circuit to measure the time-of-flight with nanosecond precision, larger ranging range and the like. However, for some scenes (such as 100 kp/s) requiring high-speed imaging, in order to ensure the ranging accuracy (c/2B, c is the light speed, B is the frequency modulation bandwidth), the frequency modulation speed (B/t, t is the single-point ranging time) is usually very fast, and in the range of several meters to hundreds of meters, the beat frequency of the echo signal and the local oscillation signal is distributed in the range of several MHz to hundreds of MHz, which poses a very great challenge to the spectrum analysis of the signal.
In the prior art, in the step of signal acquisition processing in the laser radar or millimeter wave radar applying the frequency modulation continuous wave, weak photoelectric signals are subjected to signal conditioning such as pre-amplification and filtering, firstly, filtering processing with large bandwidth, low noise and large dynamic range is performed, and then, the signals are subjected to low-pass filtering processing to attenuate various noise or interference, so that the signal to noise ratio is improved. After filtering, the signal is subjected to variable gain amplification, then high-speed analog-to-digital conversion is performed, discrete sampling is performed in the analog-to-digital converter, a digital signal is obtained, the digital signal is subjected to digital filtering and fast Fourier transformation through an FPGA (field programmable gate array), useful frequency spectrum components are extracted, and then analysis and calculation are performed, so that the distance of a measurement target is obtained. Since the frequency of the beat signal can reach hundreds of MHz at maximum, the sampling frequency of the analog-to-digital converter used according to the nyquist's law is required to reach GHz, and the computing power for performing the fast fourier transform is also required to be high, so that a high-performance analog-to-digital converter and FPGA device are required. The high-performance analog-to-digital converter and the FPGA have great disadvantages in cost, and are very great barriers to popularization of the frequency modulation continuous wave laser radar in the prior art.
Disclosure of Invention
In view of the above, the invention provides a signal spectrum analysis system and a signal spectrum analysis method for a frequency modulation continuous wave laser radar receiver, which can greatly reduce the performance requirements of an analog-to-digital converter and an FPGA and meet the requirement of the frequency modulation continuous wave laser radar on quickly searching main frequency spectrum components.
In order to achieve the above purpose, the invention provides a signal spectrum analysis system of a frequency modulation continuous wave laser radar receiver, which comprises a preprocessing module, a coarse frequency discrimination module, an FPGA module, a local oscillation signal generation module for generating a plurality of local oscillation frequencies, a frequency mixing module and an analog-to-digital conversion module,
the preprocessing module is used for filtering and gaining the received current analog electric signal and respectively transmitting the current analog electric signal after the filtering and gaining to the coarse frequency discrimination module and the frequency mixing module;
the coarse frequency discrimination module is used for carrying out frequency discrimination on the filtered and gained current analog electric signal to obtain the estimated frequency of the current analog electric signal and sending the estimated frequency to the FPGA module;
the FPGA module selects local oscillation frequency to be mixed according to the frequency of the current analog electric signal;
the local oscillation signal generation module is used for sending the local oscillation frequency selected by the FPGA module to the frequency mixing module;
the frequency mixing module mixes the filtered and gained current analog electric signal with the selected local oscillation frequency to obtain a low-frequency analog electric signal and sends the low-frequency analog electric signal to the analog-to-digital conversion module;
the analog-to-digital conversion module is used for performing analog-to-digital conversion on the low-frequency analog electric signal and sending the sampled low-frequency digital electric signal to the FPGA module;
and the FPGA module is used for carrying out Fourier transform and analysis processing on the low-frequency digital electric signals.
Preferably, the preprocessing module comprises a band-pass filter and an automatic intensity booster;
the band-pass filter carries out filtering processing on the current analog electric signal;
the automatic intensity gain device regulates and controls the signal amplitude of the current analog electric signal after filtering, and sends the signal with regulated and controlled amplitude in two paths, one path is sent to the coarse frequency discrimination module, and the other path is sent to the frequency mixing module.
Preferably, the coarse frequency discrimination module comprises a hysteresis comparator and a counter, wherein,
the hysteresis comparator is respectively provided with a higher threshold voltage and a lower threshold voltage, and when the signal amplitude of the current analog electric signal after filtering and gain is larger than the higher threshold voltage, a high-level signal is output to the counter; outputting a low-level signal to the counter when the signal amplitude of the current analog electric signal after filtering and gain is smaller than the lower threshold voltage;
the counter counts up when receiving the rising edge of the level signal to obtain the estimated frequency of the current analog electric signal.
Preferably, the coarse frequency discrimination module includes a time-to-digital converter, and the time-to-digital converter discriminates the frequency of the filtered and gained current analog electric signal to obtain an estimated current analog electric signal frequency.
Preferably, the system further comprises a multi-path gating module, wherein the multi-path gating module is respectively connected with the local oscillation signal generating module, the FPGA module and the frequency mixing module, the local oscillation signal generating module comprises a plurality of different local oscillation signal generators, and each path of input channel of the multi-path gating module inputs the corresponding local oscillation signal generator;
the FPGA module outputs gating signals to the multi-path gating module according to the frequency of the current analog electric signal;
the multipath gating module selects an input channel to be opened according to the gating signal and sends the local oscillation frequency corresponding to the input channel to the mixing module.
Preferably, the system further comprises a low-pass filtering module, wherein the low-pass filtering module is respectively connected with the mixing module and the analog-to-digital conversion module, and the low-frequency analog electric signal is sent to the analog-to-digital conversion module after being subjected to low-pass filtering.
Preferably, the number of local oscillation signal generators set in the local oscillation signal generating module depends on the frequency bandwidth range of the received analog electric signal.
Preferably, the bandwidth of the low pass filter is dependent on the number of local oscillator signal generators.
Preferably, the band-pass filter and the local oscillation frequency selected by the current analog electric signal form a passband, a plurality of passbands are formed in the frequency bandwidth range of the received analog electric signal, and the overlapped part of the two adjacent passbands is overlapped frequency, wherein the overlapped frequency is more than 10MHz.
In order to achieve the above object, the present invention provides a signal spectrum analysis method of a frequency modulation continuous wave laser radar receiver, the method comprising:
filtering and gaining the received current analog electric signal, and performing coarse frequency discrimination on the current analog electric signal after filtering and gaining to obtain the estimated frequency of the current analog electric signal;
setting a plurality of local oscillation frequencies;
selecting local oscillation frequency to be mixed according to the frequency of the current analog electric signal;
mixing the filtered and gained current analog electric signal with the selected local oscillation frequency to obtain a low-frequency analog electric signal;
performing analog-to-digital conversion on the low-frequency analog electric signal to obtain a sampled low-frequency digital electric signal;
and carrying out Fourier transformation and analysis processing on the low-frequency digital electric signals.
Compared with the prior art, the invention provides a frequency modulation continuous wave laser radar receiver signal spectrum analysis system and a frequency modulation continuous wave laser radar receiver signal spectrum analysis method, which have the following beneficial effects: the method has the advantages that the signals with a wide dynamic range (10 MHz to hundreds of MHz) are subjected to coarse frequency discrimination, and proper local oscillation frequency is selected for mixing, so that low-frequency signals with a narrow range are obtained for sampling analysis, the performance requirements of an analog-to-digital converter and an FPGA can be greatly reduced, and the requirement of rapidly searching main frequency spectrum components of the frequency modulation continuous wave laser radar is met; further improving the performance of the frequency modulation continuous wave laser radar; analyzing signals in a certain band-pass range, so that signal noise is better suppressed, and the ranging signal-to-noise ratio is improved; the circuit is simple, convenient and effective in design.
Drawings
Fig. 1 is a system schematic diagram of a frequency modulated continuous wave lidar receiver signal spectrum analysis system according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of local oscillation frequencies according to an embodiment of the present invention.
Fig. 3 is a flow chart of a method for analyzing a frequency spectrum of a frequency modulated continuous wave lidar receiver according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the specific embodiments shown in the drawings, but these embodiments are not limited to the present invention, and structural, method, or functional modifications made by those skilled in the art based on these embodiments are included in the scope of the present invention.
In one embodiment of the present invention as shown in fig. 1, the present invention provides a signal spectrum analysis system of a fm continuous wave lidar receiver, which includes a preprocessing module 10, a coarse frequency discrimination module 11, an FPGA module 12, a local oscillation signal generating module 13 for generating a plurality of local oscillation frequencies, a mixing module 14, and an analog-to-digital conversion module 15, wherein;
the preprocessing module 10 filters and gains the received current analog electric signal, and sends the filtered and gained current analog electric signal to the coarse frequency discrimination module 11 and the frequency mixing module 14 respectively;
the coarse frequency discrimination module 11 discriminates the frequency of the filtered and gained current analog electric signal to obtain the estimated frequency of the current analog electric signal, and sends the estimated frequency to the FPGA module 12;
the FPGA module 12 selects a local oscillator frequency to be mixed according to the frequency of the current analog electrical signal;
the local oscillation signal generating module 13 sends the local oscillation frequency selected by the FPGA module 12 to the mixing module 14;
the mixing module 14 mixes the filtered and gained current analog electric signal with the selected local oscillation frequency to obtain a low-frequency analog electric signal and sends the low-frequency analog electric signal to the analog-to-digital conversion module 15;
the analog-to-digital conversion module 15 performs analog-to-digital conversion on the low-frequency analog electrical signal, and sends the sampled low-frequency digital electrical signal to the FPGA module 12;
the FPGA module 12 performs fourier transform and analysis processing on the low frequency digital electrical signal.
The preprocessing module filters and gains the received current analog electric signals, and sends the current electric signals after the filtering and the gain to the coarse frequency discrimination module and the frequency mixing module respectively. The preprocessing module 10 includes a band-pass filter 101 and an automatic intensity booster 102, filters the received current analog electric signal through the band-pass filter, filters out the signal in the bandwidth, adjusts and controls the signal amplitude through the automatic intensity booster, obtains relatively stable signal amplitude, and sends the analog electric signal with the adjusted and controlled amplitude in two paths, one path is sent to the coarse frequency discrimination module, and the other path is sent to the frequency mixing module. Unnecessary noise is filtered out through a band-pass filter and an automatic intensity gain device, and the signal to noise ratio is improved.
And the coarse frequency discrimination module performs frequency discrimination on the received current analog electric signal after filtering and gain to obtain estimated current analog electric signal frequency, and then sends the estimated current analog electric signal frequency to the FPGA module. Specifically, the coarse frequency discrimination module comprises a hysteresis comparator and a counter. The hysteresis comparator is provided with two threshold voltages, namely a higher threshold voltage and a lower threshold voltage, and outputs a high-level signal to the counter when the signal amplitude of the current analog electric signal after filtering and gain is larger than the higher threshold voltage; when the signal amplitude of the current analog electric signal after filtering and gain is smaller than the lower threshold voltage, the hysteresis comparator outputs a low-level signal to the counter, and the counter accumulates and counts when receiving the rising edge of the level signal, so as to obtain the estimated frequency of the current analog electric signal. The signal frequency is estimated by using a hysteresis comparator and a counter, so that false triggering caused by signal jitter is avoided, the frequency obtained by coarse frequency discrimination estimation is much larger than the actual frequency, and the frequency obtained by estimation is more accurate. In yet another embodiment of the present invention, the coarse frequency discrimination module includes a time-to-digital converter, and the estimated current analog electric signal frequency is obtained by using the time-to-digital converter to discriminate the filtered and gained current analog electric signal.
And after receiving the frequency of the current analog electric signal, the FPGA module selects the local oscillation frequency which needs to be mixed. The local oscillation signal generation module is provided with a plurality of local oscillation frequencies, the frequencies of the current analog electric signals are different, and the selected local oscillation frequencies are different. The local oscillation signal generating module is used for directly generating a plurality of local oscillation frequencies for subsequent frequency mixing, and the requirements of high response speed and less time consumption of the existing laser radar system can be met. Specifically, the system further includes a multi-path gating module 16, the multi-path gating module 16 is respectively connected with the local oscillator signal generating module 13, the FPGA module 12 and the mixing module 14, the local oscillator signal generating module includes a plurality of different local oscillator signal generators, the gating module includes multiple paths of input channels, each path of input channel of the multi-path gating module inputs a corresponding local oscillator signal generator, the FPGA module outputs a gating signal to the multi-path gating module according to the frequency of the current analog electrical signal, and the multi-path gating module selects an input channel to be opened according to the gating signal and sends the local oscillator frequency corresponding to the input channel to the mixing module. Based on the estimated signal frequency, the FPGA module controls which channel of the multi-channel gating module is opened, and each channel is opened, and proper local oscillation frequency is selected for mixing.
The frequency mixing module mixes the received current analog electric signal after filtering and gain with the selected local oscillation frequency, down-converts the analog electric signal to obtain a low-frequency analog electric signal and sends the low-frequency analog electric signal to the analog-to-digital conversion module.
According to an embodiment of the present invention, the system further includes a low-pass filtering module 17, where the low-pass filtering module 17 is connected to the mixing module 14 and the analog-to-digital conversion module 15, and sends the low-frequency analog electrical signal to the analog-to-digital conversion module 15 after performing a low-pass filtering process. The analog-to-digital conversion module carries out analog-to-digital conversion on the low-frequency analog electric signal after the low-pass filtering processing, and sends the sampled low-frequency digital electric signal to the FPGA module. The FPGA module performs Fourier transform and analysis processing on the low-frequency digital signal. The FPGA module only analyzes signals in a certain band pass, so that noise can be well suppressed, and the ranging signal-to-noise ratio is improved.
According to an embodiment of the present invention, the number of local oscillation signal generators provided in the local oscillation signal generating module depends on the frequency bandwidth range of the received analog electrical signal. The bandwidth of the low pass filter depends on the number of local oscillator signal generators. The user can select the proper number of local oscillation frequencies according to the frequency bandwidth of the received signal, the bandwidth of the low-pass filter is selected according to the number of local oscillation frequencies, and passband frequencies corresponding to the combination of the local oscillation frequencies and the low-pass filter are overlapped to cover the frequency bandwidth of the received signal, as shown in a frequency overlapping schematic diagram in fig. 2. According to the nyquist's law and the practical application of the application, the sampling speed of the analog-to-digital conversion module should be at least more than 2.5 times of the bandwidth of the low-pass filter, so that the more the number of the local oscillation signal generators is set, the smaller the interval between adjacent local oscillation frequencies is, the narrower the bandwidth of the selected low-pass filter is, the lower the performance requirement of the analog-to-digital conversion module is, conversely, the fewer the number of the local oscillation signal generators is, the more the interval between adjacent local oscillation frequencies is, the wider the bandwidth of the selected low-pass filter is, and the performance requirement of the analog-to-digital conversion module is higher, as shown in fig. 2. Considering that the speed of the target object (mostly 10 m/s) can bring about multi-frequency spectrum components, and that the adjacent object of the target object can also bring about multi-frequency spectrum components, the interval between two adjacent local oscillator frequencies is not suitable to be set too small, so that all the frequency spectrum components can be captured by the low-pass filter in single imaging. For example, in a specific embodiment, the interval between two adjacent local oscillation frequencies is set to 80MHz, the bandwidth of the low-pass filter is 50MHz, the sampling speed of the analog-to-digital conversion module is 150MSPS, and the calculation requirement of the fourier transform corresponding to the FPGA module is 8uS to realize the fourier transform of 1600 points. This is a very considerable device simplification compared to an analog to digital conversion module of 1GSPS, and its corresponding 8uS implementing an 8k point fourier transform FPGA.
In order to ensure that two spectral components corresponding to each object are collected (the doppler effect causes the frequency to be torn into two frequencies within 10MHz apart), and that all spectral components adjacent to a plurality of objects (within a few meters) form a passband with the local oscillator frequency selected by the current analog electrical signal, a plurality of passbands are formed within the frequency bandwidth of the received analog electrical signal, and the overlapping part of two adjacent passbands is an overlapping frequency, which is greater than 10MHz, as shown in fig. 2.
According to the technical scheme, for the imaging speed (100 KHz level) of a common laser radar, from 5 meters to more than 100 meters, the beat frequency corresponding to a laser signal is in the range of 10MHz to hundreds of MHz, the signal with a wide dynamic range is subjected to coarse frequency discrimination, and the proper local oscillation frequency is selected for mixing, so that the low-frequency signal with a narrow range is obtained for sampling analysis, and the performance requirements of an analog-digital converter and an FPGA device are reduced.
In one embodiment of the present invention as shown in fig. 3, the present invention provides a method for analyzing a signal spectrum of a frequency modulated continuous wave lidar receiver, the method comprising:
s301, filtering and gaining the received current analog electric signal, and performing coarse frequency discrimination on the current analog electric signal after filtering and gaining to obtain estimated frequency of the current analog electric signal;
s302, setting a plurality of local oscillation frequencies;
s303, selecting local oscillation frequency to be mixed according to the frequency of the current analog electric signal;
s304, mixing the filtered and gained current analog electric signal with the selected local oscillation frequency to obtain a low-frequency analog electric signal;
s305, performing analog-to-digital conversion on the low-frequency analog electric signal to obtain a sampled low-frequency digital electric signal;
s306, carrying out Fourier transformation and analysis processing on the low-frequency digital signal.
And filtering and gaining the received current analog electric signal, and performing coarse frequency discrimination on the current analog electric signal after filtering and gaining to obtain the estimated current analog electric signal frequency. And selecting the local oscillation frequency to be mixed according to the frequency of the current analog electric signal. The device is provided with a plurality of local oscillation frequencies, the frequencies of the current analog electric signals are different, and the selected local oscillation frequencies are different. And mixing the received current analog electric signal after filtering and gain with a local oscillation frequency, and performing down-conversion on the analog electric signal to obtain a low-frequency analog electric signal. And performing analog-to-digital conversion on the low-frequency analog electric signal after performing low-pass filtering processing to obtain a sampled low-frequency digital electric signal. And carrying out Fourier transformation and analysis processing on the low-frequency digital electric signals.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (10)
1. A signal spectrum analysis system of a frequency modulation continuous wave laser radar receiver is characterized by comprising a preprocessing module, a coarse frequency discrimination module, an FPGA module, a local oscillation signal generation module for generating a plurality of local oscillation frequencies, a frequency mixing module and an analog-to-digital conversion module,
the preprocessing module is used for filtering and gaining the received current analog electric signal and respectively transmitting the current analog electric signal after the filtering and gaining to the coarse frequency discrimination module and the frequency mixing module;
the coarse frequency discrimination module is used for carrying out frequency discrimination on the filtered and gained current analog electric signal to obtain the estimated frequency of the current analog electric signal and sending the estimated frequency to the FPGA module;
the FPGA module selects local oscillation frequency to be mixed according to the frequency of the current analog electric signal;
the local oscillation signal generation module is used for sending the local oscillation frequency selected by the FPGA module to the frequency mixing module;
the frequency mixing module mixes the filtered and gained current analog electric signal with the selected local oscillation frequency to obtain a low-frequency analog electric signal and sends the low-frequency analog electric signal to the analog-to-digital conversion module;
the analog-to-digital conversion module is used for performing analog-to-digital conversion on the low-frequency analog electric signal and sending the sampled low-frequency digital electric signal to the FPGA module;
and the FPGA module is used for carrying out Fourier transform and analysis processing on the low-frequency digital electric signals.
2. The fm continuous wave lidar receiver signal spectrum analysis system of claim 1, wherein the preprocessing module comprises a bandpass filter and an automatic intensity booster;
the band-pass filter carries out filtering processing on the current analog electric signal;
the automatic intensity gain device regulates and controls the signal amplitude of the current analog electric signal after filtering, and sends the signal with regulated and controlled amplitude in two paths, one path is sent to the coarse frequency discrimination module, and the other path is sent to the frequency mixing module.
3. The system for spectrum analysis of a signal of a frequency modulated continuous wave lidar receiver of claim 1, wherein the coarse frequency discrimination module comprises a hysteresis comparator and a counter, wherein,
the hysteresis comparator is respectively provided with a higher threshold voltage and a lower threshold voltage, and when the signal amplitude of the current analog electric signal after filtering and gain is larger than the higher threshold voltage, a high-level signal is output to the counter; outputting a low-level signal to the counter when the signal amplitude of the current analog electric signal after filtering and gain is smaller than the lower threshold voltage;
the counter counts up when receiving the rising edge of the level signal to obtain the estimated frequency of the current analog electric signal.
4. The fm continuous wave lidar receiver signal spectrum analysis system of claim 2, wherein the coarse frequency discrimination module comprises a time-to-digital converter that discriminates the filtered and gained current analog electrical signal to obtain an estimated current analog electrical signal frequency.
5. A fm continuous wave lidar receiver signal spectrum analysis system as claimed in claim 3, wherein said system further comprises a multi-pass gating module, said multi-pass gating module being respectively connected to said local oscillator signal generation module, FPGA module, and mixer module, said local oscillator signal generation module comprising a plurality of different local oscillator signal generators, each input channel of said multi-pass gating module inputting a corresponding local oscillator signal generator;
the FPGA module outputs gating signals to the multi-path gating module according to the frequency of the current analog electric signal;
the multipath gating module selects an input channel to be opened according to the gating signal and sends the local oscillation frequency corresponding to the input channel to the mixing module.
6. The system for spectrum analysis of signals of a frequency modulated continuous wave lidar receiver of claim 5, further comprising a low pass filter module, wherein the low pass filter module is connected to the mixing module and the analog-to-digital conversion module, respectively, and the low frequency analog electrical signal is sent to the analog-to-digital conversion module after being subjected to low pass filtering.
7. The system of claim 6, wherein the number of local oscillator signal generators provided in the local oscillator signal generation module is dependent on a frequency bandwidth range of the received analog electrical signal.
8. The system of claim 7, wherein the bandwidth of the low pass filter module is dependent on the number of local oscillator signal generators.
9. The system of claim 2, wherein the bandpass filter and the local oscillator frequency selected by the current analog signal form a passband, a plurality of passbands are formed within the frequency bandwidth of the received analog signal, and overlapping portions of two adjacent passbands are overlapping frequencies, wherein the overlapping frequencies are greater than 10MHz.
10. A method for spectrum analysis of a signal of a frequency modulated continuous wave lidar receiver, the method comprising:
filtering and gaining the received current analog electric signal, and performing coarse frequency discrimination on the current analog electric signal after filtering and gaining to obtain the estimated frequency of the current analog electric signal;
setting a plurality of local oscillation frequencies;
selecting local oscillation frequency to be mixed according to the frequency of the current analog electric signal;
mixing the filtered and gained current analog electric signal with the selected local oscillation frequency to obtain a low-frequency analog electric signal;
performing analog-to-digital conversion on the low-frequency analog electric signal to obtain a sampled low-frequency digital electric signal;
and carrying out Fourier transformation and analysis processing on the low-frequency digital electric signals.
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