CN112068105A - Frequency modulation continuous wave laser radar receiver signal spectrum analysis system and method - Google Patents
Frequency modulation continuous wave laser radar receiver signal spectrum analysis system and method Download PDFInfo
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- 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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- 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
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Abstract
The invention discloses a frequency modulation continuous wave laser radar receiver signal frequency spectrum analysis system, which carries out filtering and gain on a received current analog electric signal, carries out coarse frequency discrimination on the filtered and gained current analog electric signal to obtain an estimated current analog electric signal frequency, selects a local oscillator frequency needing frequency mixing, carries out frequency mixing on the filtered and gained current analog electric signal and the local oscillator frequency to obtain a low-frequency analog electric signal, carries out low-pass filtering processing on the low-frequency analog electric signal and then carries out Fourier transform and analysis processing, and can greatly reduce the performance requirements of an analog-to-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 concerned and applied in the fields of radars and laser radars. Compared with the traditional flight time ranging, the frequency modulation continuous wave has the outstanding advantages of coherent detection, interference resistance, no need of instantaneous high power, no need of a high-speed circuit for measuring the flight time with nanosecond precision, larger ranging range and the like. However, for some scenes (such as 100kp/s) requiring high-speed imaging, in order to ensure the ranging accuracy (c/2B, c is the speed of light, and B is the bandwidth of frequency modulation), 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 several hundred meters, the beat frequency of the echo signal and the local oscillator signal is distributed in several MHz to several hundred MHz, which poses a great challenge to the spectrum analysis of the signal.
At present, in a laser radar or a millimeter wave radar applying frequency modulation continuous waves, signal acquisition and processing steps mainly include signal conditioning such as early amplification and filtering of weak photoelectric signals, firstly, filtering processing with large bandwidth, low noise and large dynamic range, and then, low-pass filtering processing for attenuating various noises or interferences and improving the signal-to-noise ratio. After filtering, the signal is subjected to variable gain amplification, then high-speed analog-to-digital conversion is carried out, discrete sampling is carried out in an analog-to-digital converter to obtain a digital signal, the digital signal is subjected to digital filtering and fast Fourier transform through an FPGA (field programmable gate array), useful frequency spectrum components are extracted, and then analysis and calculation are carried out to obtain the distance of a measurement target. The maximum frequency of the beat frequency signal can reach hundreds of MHz, the sampling frequency of an analog-digital converter adopted according to the Nyquist law can be required to reach GHz, and meanwhile, the calculation capability of fast Fourier transform is also required to be high, so that a high-performance analog-digital converter and an FPGA device are required. The high-performance analog-to-digital converter and the FPGA have great disadvantages in cost, and are very great obstacles to popularization of the frequency modulation continuous wave laser radar in the prior art.
Disclosure of Invention
In view of this, the invention provides a system and a method for analyzing a frequency spectrum of a frequency modulated 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 modulated continuous wave laser radar for quickly searching a main frequency spectrum component.
In order to achieve the above object, the present invention provides a frequency modulation continuous wave lidar receiver signal spectrum analysis system, which comprises a preprocessing module, a coarse frequency discrimination module, an FPGA module, a local oscillator signal generation module for generating a plurality of local oscillator frequencies, a frequency mixing module, and an analog-to-digital conversion module, wherein,
the preprocessing module is used for filtering and gaining the received current analog electric signal and respectively sending the filtered and gained current analog electric signal to the coarse frequency discrimination module and the frequency mixing module;
the coarse frequency discrimination module is used for performing 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 a local oscillation frequency needing frequency mixing according to the frequency of the current analog electric signal;
the local oscillation signal generating module is used for sending the local oscillation frequency selected by the FPGA module to the frequency mixing module;
the frequency mixing module is used for mixing the filtered and gained current analog electric signal with the selected local oscillator frequency to obtain a low-frequency analog electric signal and sending 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 signal.
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 booster regulates and controls the signal amplitude of the filtered current analog electric signal, and sends the amplitude-regulated signal 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 filtered and gained current analog electric signal is greater than the higher threshold voltage, a high-level signal is output to the counter; when the signal amplitude of the current analog electric signal after filtering and gain is smaller than the lower threshold voltage, outputting a low-level signal to the counter;
and the counter accumulates and counts 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 performs frequency discrimination on the filtered and gained current analog electrical signal to obtain an estimated frequency of the current analog electrical signal.
Preferably, the system further comprises a multi-channel gating module, the multi-channel 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 input channel of the multi-channel gating module inputs a corresponding local oscillation signal generator;
the FPGA module outputs a gating signal to the multi-channel gating module according to the frequency of the current analog electric signal;
and the multi-path 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 frequency mixing module.
Preferably, the system further includes a low-pass filtering module, where the low-pass filtering module is connected to the frequency mixing module and the analog-to-digital conversion module, and performs low-pass filtering on the low-frequency analog electrical signal and then sends the low-frequency analog electrical signal to the analog-to-digital conversion module.
Preferably, the number of the local oscillator signal generators provided in the local oscillator signal generation module depends on the frequency bandwidth range of the received analog electrical signal.
Preferably, the bandwidth of the low-pass filter depends on the number of the local oscillator signal generators.
Preferably, the band-pass filter and a local oscillation frequency selected by the current analog electrical signal form a pass band, and form a plurality of pass bands within a frequency bandwidth range of the received analog electrical signal, and a part overlapped by two adjacent pass bands is an overlapped frequency, where the overlapped frequency is greater than 10 MHz.
In order to achieve the above object, the present invention provides a frequency modulation continuous wave lidar receiver signal spectrum analysis method, which comprises:
filtering and gaining the received current analog electric signal, and carrying out coarse frequency discrimination on the filtered and gained current analog electric signal to obtain the estimated frequency of the current analog electric signal;
setting a plurality of local oscillation frequencies;
selecting a local oscillator frequency needing frequency mixing 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 transform and analysis processing on the low-frequency digital electric signal.
Compared with the prior art, the invention provides a frequency modulation continuous wave laser radar receiver signal spectrum analysis system and a method, which bring the following beneficial effects: the method has the advantages that the signals in a wide dynamic range (10MHz to hundreds of MHz) are subjected to coarse frequency discrimination, and proper local oscillation frequency is selected for frequency mixing, so that low-frequency signals in a narrow range are obtained for sampling analysis, the performance requirements of an analog-digital converter and an FPGA (field programmable gate array) can be greatly reduced, and the requirement of a frequency modulation continuous wave laser radar for quickly searching for main frequency spectrum components is met; the performance of the frequency modulation continuous wave laser radar is further improved; signals in a certain band-pass range are analyzed, 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 diagram of a frequency modulated continuous wave lidar receiver signal spectrum analysis system according to one embodiment of the invention.
Fig. 2 is a schematic diagram of local oscillation frequencies according to an embodiment of the present invention.
Fig. 3 is a schematic flow diagram of a method for frequency spectrum analysis of a frequency modulated continuous wave lidar receiver signal according to an embodiment of the invention.
Detailed Description
The present invention will be described in detail with reference to the specific embodiments shown in the drawings, which are not intended to limit the present invention, and structural, methodological, or functional changes made by those skilled in the art according to the specific embodiments are included in the scope of the present invention.
As shown in fig. 1, according to an embodiment of the present invention, the present invention provides a frequency modulation continuous wave lidar receiver signal spectrum analysis system, which includes a preprocessing module 10, a coarse frequency discrimination module 11, an FPGA module 12, a local oscillator signal generation module 13 generating a plurality of local oscillator frequencies, a frequency mixing module 14, and an analog-to-digital conversion module 15, where;
the preprocessing module 10 is configured to filter and gain the received current analog electrical signal, and send the filtered and gained current analog electrical signal to the coarse frequency discrimination module 11 and the frequency mixing module 14, respectively;
the coarse frequency discrimination module 11 performs frequency discrimination on the filtered and gained current analog electrical signal to obtain an estimated frequency of the current analog electrical signal, and sends the estimated frequency to the FPGA module 12;
the FPGA module 12 selects a local oscillation frequency to be mixed according to the frequency of the current analog electrical signal;
the local oscillation signal generating module 13 is configured to send the local oscillation frequency selected by the FPGA module 12 to the frequency mixing module 14;
the frequency mixing module 14 is configured to mix the filtered and gained current analog electrical signal with the selected local oscillator frequency to obtain a low-frequency analog electrical signal, and send the low-frequency analog electrical 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 signal, and respectively sends the filtered and gained current electric signal to the coarse frequency discrimination module and the frequency mixing module. The preprocessing module 10 includes a band-pass filter 101 and an automatic strength gaining device 102, and the received current analog electrical signal passes through the band-pass filter first, and the signal is filtered, and the signal in the bandwidth is filtered out, and then the signal amplitude is regulated and controlled by the automatic strength gaining device, so that a relatively stable signal amplitude is obtained, and the analog electrical signal with the regulated and controlled amplitude is sent 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 booster, and the signal-to-noise ratio is improved.
And the coarse frequency discrimination module performs frequency discrimination on the received filtered and gained current analog electric signal to obtain the 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 which are respectively a higher threshold voltage and a lower threshold voltage, and when the signal amplitude of the filtered and gained current analog electric signal is greater than the higher threshold voltage, the hysteresis comparator outputs a high-level signal to the counter; when the signal amplitude of the filtered and gained current analog electric signal 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 to obtain the estimated frequency of the current analog electric signal. The estimation of the signal frequency is carried out by using the hysteresis comparator and the 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 estimated frequency is more accurate. In yet another embodiment of the present invention, the coarse frequency discrimination module includes a time-to-digital converter, and the frequency of the filtered and gained current analog electrical signal is discriminated by using the time-to-digital converter to obtain the estimated frequency of the current analog electrical signal.
And after receiving the frequency of the current analog electric signal, the FPGA module selects the local oscillation frequency needing frequency mixing. The local oscillator signal generation module is provided with a plurality of local oscillator frequencies, the frequencies of the current analog electrical signals are different, and the selected local oscillator frequencies are different. A plurality of local oscillation frequencies are directly generated through the local oscillation signal generation module so as to be used in subsequent frequency mixing, and the requirements of high response speed and low time consumption of the existing laser radar system can be met. Specifically, the system further includes a multiple-way gating module 16, where the multiple-way gating module 16 is connected to the local oscillator signal generating module 13, the FPGA module 12, and the frequency mixing module 14, the local oscillator signal generating module includes a plurality of different local oscillator signal generators, the gating module includes multiple input channels, each input channel of the multiple-way gating module inputs a corresponding local oscillator signal generator, the FPGA module outputs a gating signal to the multiple-way gating module according to the frequency of the current analog electrical signal, and the multiple-way 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 frequency 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 selects a proper local oscillation frequency for frequency mixing.
And the frequency mixing module is used for mixing the received filtered and gained current analog electric signal with the selected local oscillator frequency, performing down-conversion on the analog electric signal to obtain a low-frequency analog electric signal and sending the low-frequency analog electric signal to the analog-to-digital conversion module.
According to a specific embodiment of the present invention, the system further includes a low-pass filtering module 17, where the low-pass filtering module 17 is respectively connected to the frequency 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 low-pass filtering processing. The analog-to-digital conversion module performs analog-to-digital conversion on the low-frequency analog electric signal subjected to the low-pass filtering processing, and sends the sampled low-frequency digital electric signal to the FPGA module. And the FPGA module performs Fourier transform and analysis processing on the low-frequency digital electric signal. The FPGA module only analyzes signals in a certain band pass, so that noise can be better suppressed, and the ranging signal-to-noise ratio is improved.
According to an embodiment of the present invention, the number of the local oscillator signal generators provided in the local oscillator 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 the local oscillator signal generators. A user may select the number of suitable local oscillation frequencies according to the frequency bandwidth of the received signal, the bandwidth of the low-pass filter may be selected according to the number of local oscillation frequencies, and the passband frequencies corresponding to the combination of the local oscillation frequencies and the low-pass filter may be superimposed to cover the frequency bandwidth of the received signal, as shown in the frequency superimposition diagram of fig. 2. As can be known from nyquist's law and practical application, the sampling speed of the analog-to-digital conversion module should be at least 2.5 times the bandwidth of the low-pass filter, so that the larger the number of the local oscillator signal generators, the smaller the interval between adjacent local oscillator frequencies, the narrower the bandwidth of the selected low-pass filter, and the lower the performance requirement on the analog-to-digital conversion module, and conversely, the smaller the number of the local oscillator signal generators, the larger the interval between adjacent local oscillator frequencies, the wider the bandwidth of the selected low-pass filter, and the higher the performance requirement on the analog-to-digital conversion module, as shown in fig. 2. Considering that the multi-spectral components are brought by the velocity of the target object (mostly 10m/s) and the multi-spectral components are brought by the object adjacent to the target object, the interval between two adjacent local oscillation frequencies is not set too small, and it can be ensured that all the spectral components can be captured by the low-pass filter in a single imaging. For example, in a specific embodiment, the interval between two adjacent local oscillator frequencies is set to be 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 1600-point fourier transform. Compared with an analog-to-digital conversion module of 1GSPS and an FPGA which realizes 8 k-point Fourier transform by corresponding 8uS, the FPGA has considerable device simplification.
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 all the spectral components of several objects (within several meters) are collected, the band pass filter and the local oscillation frequency selected by the current analog electric signal form a pass band, and form a plurality of pass bands within the frequency bandwidth range of the received analog electric signal, and the overlapped part of the two adjacent pass bands is an overlapped frequency, and the overlapped frequency is greater than 10MHz, such as the overlapped frequency shown in fig. 2.
According to the technical scheme, for the imaging speed (100KHz 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 from 10MHz to hundreds of MHz, the signal in a wide dynamic range is subjected to coarse frequency discrimination, and an appropriate local oscillation frequency is selected for frequency mixing, so that a low-frequency signal in a narrow range is obtained for sampling analysis, and the performance requirements of an analog-to-digital converter and an FPGA device are lowered.
In an embodiment of the present invention as shown in fig. 3, the present invention provides a frequency modulation continuous wave lidar receiver signal spectrum analysis method, which includes:
s301, filtering and gaining the received current analog electric signal, and carrying out coarse frequency discrimination on the filtered and gained current analog electric signal to obtain the estimated frequency of the current analog electric signal;
s302, setting a plurality of local oscillation frequencies;
s303, selecting a local oscillation frequency needing frequency mixing 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;
and S306, carrying out Fourier transform and analysis processing on the low-frequency digital electric signal.
And filtering and gaining the received current analog electric signal, and carrying out coarse frequency discrimination on the filtered and gained current analog electric signal to obtain the estimated frequency of the current analog electric signal. And selecting the local oscillation frequency required to be mixed according to the frequency of the current analog electric signal. A plurality of local oscillation frequencies are set, 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 the local oscillation frequency, and performing down-conversion on the analog electric signal to obtain a low-frequency analog electric signal. And carrying out low-pass filtering processing on the low-frequency analog electric signal, and then carrying out analog-to-digital conversion to obtain a sampled low-frequency digital electric signal. And carrying out Fourier transform and analysis processing on the low-frequency digital electric signal.
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 frequency modulation continuous wave laser radar receiver signal frequency spectrum analysis system is characterized by comprising a preprocessing module, a coarse frequency discrimination module, an FPGA module, a local oscillator signal generation module for generating a plurality of local oscillator frequencies, a frequency mixing module and an analog-to-digital conversion module, wherein,
the preprocessing module is used for filtering and gaining the received current analog electric signal and respectively sending the filtered and gained current analog electric signal to the coarse frequency discrimination module and the frequency mixing module;
the coarse frequency discrimination module is used for performing 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 a local oscillation frequency needing frequency mixing according to the frequency of the current analog electric signal;
the local oscillation signal generating module is used for sending the local oscillation frequency selected by the FPGA module to the frequency mixing module;
the frequency mixing module is used for mixing the filtered and gained current analog electric signal with the selected local oscillator frequency to obtain a low-frequency analog electric signal and sending 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 signal.
2. A frequency modulated continuous wave lidar receiver signal spectrum analysis system as defined in claim 1 wherein 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 booster regulates and controls the signal amplitude of the filtered current analog electric signal, and sends the amplitude-regulated signal 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. A frequency modulated continuous wave lidar receiver signal spectrum analysis system as defined in claim 1 wherein the coarse frequency discrimination module comprises a hysteretic 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 filtered and gained current analog electric signal is greater than the higher threshold voltage, a high-level signal is output to the counter; when the signal amplitude of the current analog electric signal after filtering and gain is smaller than the lower threshold voltage, outputting a low-level signal to the counter;
and the counter accumulates and counts when receiving the rising edge of the level signal to obtain the estimated frequency of the current analog electric signal.
4. A frequency modulated continuous wave lidar receiver signal spectrum analysis system as defined in 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 frequency modulated continuous wave lidar receiver signal spectrum analysis system as claimed in claim 3, further comprising a multiple-way gating module, said multiple-way gating module being connected to said local oscillator signal generation module, said FPGA module, and said mixer module, respectively, said local oscillator signal generation module comprising a plurality of different local oscillator signal generators, each input channel of said multiple-way gating module inputting a corresponding local oscillator signal generator;
the FPGA module outputs a gating signal to the multi-channel gating module according to the frequency of the current analog electric signal;
and the multi-path 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 frequency mixing module.
6. A frequency modulated continuous wave lidar receiver signal spectrum analysis system as claimed in claim 5, further comprising a low pass filtering module, wherein the low pass filtering module is connected to the frequency mixing module and the analog-to-digital conversion module respectively, for low pass filtering the low frequency analog electrical signal and then sending the low frequency analog electrical signal to the analog-to-digital conversion module.
7. A frequency modulated continuous wave lidar receiver signal spectrum analysis system as claimed in claim 6, wherein the number of local oscillator signal generators provided in the local oscillator signal generation module is dependent on the frequency bandwidth range of the received analog electrical signal.
8. A frequency modulated continuous wave lidar receiver signal spectrum analysis system as claimed in claim 7, wherein the bandwidth of the low pass filter is dependent on the number of local oscillator signal generators.
9. A frequency modulated continuous wave lidar receiver signal spectrum analysis system as claimed in claim 8 wherein the bandpass filter forms a passband with a local oscillator frequency selected for the current analog electrical signal, forming a plurality of passbands within the frequency bandwidth of the received analog electrical signal, the overlapping portion of two adjacent passbands being an overlapping frequency, wherein the overlapping frequency is greater than 10 MHz.
10. A method for frequency-modulated continuous wave lidar receiver signal spectrum analysis, the method comprising:
filtering and gaining the received current analog electric signal, and carrying out coarse frequency discrimination on the filtered and gained current analog electric signal to obtain the estimated frequency of the current analog electric signal;
setting a plurality of local oscillation frequencies;
selecting a local oscillator frequency needing frequency mixing 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 transform and analysis processing on the low-frequency digital electric signal.
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