A non-aliasing frequency modulated continuous wave radar detection system and method

Abstract

The present application relates to the technical field of laser radar, and especially relates to a non-aliasing frequency modulation continuous wave radar detection system and method, the non-aliasing frequency modulation continuous wave radar detection system comprising: a light source, a beam splitter, a circulator, a 90-degree frequency mixer, a signal conversion module and a signal processing unit, the signal processing unit being configured to: construct a complex vector signal S based on a first electrical signal I and a second electrical signal Q, S=I+jQ, wherein j is an imaginary operator, and obtain a double sideband spectrum based on the complex vector signal S, determine the frequency of a signal peak in an up-sweeping frequency period and the frequency of a signal peak in a down-sweeping frequency period in the double sideband spectrum, and obtain the distance and speed of a target to be detected based on the frequency of the signal peak in the up-sweeping frequency period and the frequency of the signal peak in the down-sweeping frequency period.The present application is at least beneficial to solve the signal aliasing problem when detecting the target to be detected.

Description

Technical Field

[0001] This invention belongs to the field of lidar technology, and particularly relates to a non-aliasing frequency-modulated continuous wave radar detection system and method. Background Technology

[0002] With the rapid development of modern industry and technology, lidar technology has been widely applied in many fields, such as unmanned vehicles, underwater target detection, and meteorological observation. Among them, frequency-modulated continuous wave (FMCW) lidar has attracted much attention due to its high sensitivity, large dynamic range, and excellent resolution. Lidar emits continuous wave laser light with a frequency that varies linearly with time and receives the laser light reflected from the target, using the frequency difference between the emitted and reflected signals to measure the target's distance and velocity.

[0003] However, in practical applications, FMCW lidar faces a key challenge: when the target speed is high or the distance is close, Doppler frequency shift may cause spectral aliasing, resulting in errors in the measurement results of distance and velocity. Summary of the Invention

[0004] In view of this, the present invention aims to provide a non-aliasing frequency-modulated continuous wave radar detection system and method, which at least helps to solve the signal aliasing problem when detecting the target.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0006] This invention provides a non-aliasing frequency-modulated continuous wave radar detection system, comprising: a light source for emitting detection light; a beam splitter for splitting the detection light into a local oscillator beam and an emitted beam; a circulator for emitting the emitted beam after passing through the circulator, and for reflecting the emitted beam after being reflected by the target to form a reflected beam, which is received by the circulator; a 90-degree mixer for interfering the local oscillator beam and the reflected beam to generate orthogonal first and second optical signals; a signal conversion module for converting the first optical signal into a first electrical signal I and the second optical signal into a second electrical signal Q, wherein both the first electrical signal I and the second electrical signal Q are digital signals; and a signal processing unit configured to: construct a composite vector signal S, S = I + jQ, based on the first electrical signal I and the second electrical signal Q, where j is the imaginary part operator, and obtain a double-sideband spectrum based on the composite vector signal S to determine the frequency of the signal peak within the upper sweep period of the double-sideband spectrum. and the frequency of the signal peak within the lower sweep cycle Based on the frequency of the signal peak within the up-sweep cycle and the frequency of the signal peak within the lower sweep cycle Obtain the distance and speed of the target to be tested.

[0007] Furthermore, the signal processing unit uses the frequency of the signal peak within the up-sweep period of the double-sideband spectrum. and the frequency of the signal peak within the lower sweep cycle Obtaining the distance and velocity of the target involves: obtaining the distance and velocity of the target based on Formula 1, as follows:

[0008] Where d is the distance to the target, v is the velocity of the target, T is the triangular wave period of the probe light, BW is the linear frequency modulation bandwidth, λ is the wavelength of the probe light, and c is the speed of light.

[0009] Furthermore, the signal conversion module includes a photodetector and an analog-to-digital converter. The photodetector converts the first optical signal into a first analog electrical signal and the second optical signal into a second analog electrical signal. The analog-to-digital converter converts the first analog electrical signal into a first electrical signal I and the second analog electrical signal into a second electrical signal Q.

[0010] Furthermore, the expressions for the first analog electrical signal I(t) and the second analog electrical signal Q(t) are as follows:

[0011] Where R is the responsivity of the photodetector. The Doppler frequency shift is the frequency shift caused by the motion of the target object, and t is time. For flight time intervals, For linear frequency modulation rate, T is the triangular wave period of the probe light, and BW is the linear frequency modulation bandwidth.

[0012] Furthermore, composite vector signals , and When the interval is -, it represents the up-sweep frequency period. and When the value is +, it represents the downsweep frequency period.

[0013] Furthermore, the signal processing unit obtains the double-sideband spectrum based on the composite vector signal S by performing a fast Fourier transform on the composite vector signal to obtain the double-sideband spectrum.

[0014] Furthermore, the first optical signal includes two first signals with opposite phases, and the second optical signal includes two second signals with opposite phases. The light intensities of the two first signals with opposite phases are I1(t) and I2(t), respectively, and the light intensities of the two second signals with opposite phases are I3(t) and I4(t), respectively.

[0015] ,in, The Doppler frequency shift is the frequency shift caused by the motion of the target object, and t is time. For flight time intervals, It is a linear frequency modulation rate.

[0016] Furthermore, the probe light is a triangular-wavelength frequency-modulated continuous-wave laser, and the electric field of the probe light during the upper frequency sweep period... and the electric field of the probe light during the lower frequency sweep period Satisfy the following expression:

[0017] ;in, The initial optical frequency, t is the linear frequency modulation rate, T is the period of the triangular wave, and t is time.

[0018] Furthermore, the electric field of the emitted beam during the upper frequency sweep period and the electric field of the emitted beam during the lower frequency sweep period Satisfy the following expression:

[0019] ;in, The electric field amplitude of the emitted beam; the electric field of the local oscillator beam during the up-sweep period. The electric field of the local oscillator beam during the lower sweep frequency period Satisfy the following expression:

[0020] ;in, The electric field amplitude of the local oscillator beam; the electric field of the reflected beam during the upper sweep period. The electric field of the reflected beam during the lower frequency sweep period as follows:

[0021] ;in, The amplitude of the reflected light beam. This refers to the flight time interval.

[0022] This invention provides, in another aspect, a non-aliasing frequency-modulated continuous wave radar detection method. This method is based on the aforementioned non-aliasing frequency-modulated continuous wave radar detection system and includes: emitting detection light using a light source; splitting the detection light into a local oscillator beam and a transmitted beam using a beam splitter; emitting the transmitted beam through a circulator and reflecting it off the target to form a reflected beam; receiving the reflected beam using a circulator; interfering the local oscillator beam and the reflected beam using a 90-degree mixer to generate orthogonal first and second optical signals; converting the first optical signal into a first electrical signal I and the second optical signal into a second electrical signal Q using a signal conversion module, where both the first and second electrical signals I and Q are digital signals; and using a signal processing unit to construct a composite vector signal S based on the first and second electrical signals I and Q, S = I + jQ, where j is the imaginary part operator, and obtaining the double-sideband spectrum based on the composite vector signal S to determine the frequency of the signal peak within the upper sweep period of the double-sideband spectrum. and the frequency of the signal peak within the lower sweep cycle Based on the frequency of the signal peak within the up-sweep cycle and the frequency of the signal peak within the lower sweep cycle Obtain the distance and speed of the target to be tested.

[0023] Compared with existing technologies, the present invention achieves the following beneficial effects: The non-aliasing frequency-modulated continuous wave radar detection system and method provided by the present invention uses a 90-degree mixer to acquire a first optical signal and a second optical signal, and uses a signal conversion module to convert the first optical signal into a first electrical signal I and the second optical signal into a second electrical signal Q. In the signal processing stage, a composite vector signal S is constructed and a fast Fourier transform is performed to obtain a double-sideband spectrum. The double-sideband spectrum is a spectrum with negative frequencies, avoiding the signal aliasing problem of traditional single-sideband structures. Moreover, the non-aliasing frequency-modulated continuous wave radar detection system provided by the present invention does not require an IQ modulator and an arbitrary waveform generator, and does not require complex optical field modulation. The system is simple and low in cost. It does not require frequency shifting of an acousto-optic modulator, thus reducing the data acquisition rate, cost, and power consumption. The FMCW laser modulation provided by the present invention only uses the most basic triangular wave, and the signal processing only requires FFT (Fast Fourier Transform) operation, without the need for complex algorithms. Both signal modulation and signal processing are relatively simple. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 A schematic diagram of the structure of the non-aliasing frequency-modulated continuous wave radar detection system described in an embodiment of the present invention. Detailed Implementation

[0026] Analysis revealed that during target detection using FMCW lasers, the probe light is reflected by the target to form reflected light. The expression for the intermediate frequency signal obtained based on the reflected light is as follows:

[0027] ;

[0028] in, For linear frequency modulation rate, For flight time intervals, For Doppler frequency shift, This represents the current output by the balanced detector during the upper frequency sweep cycle. For the current output of the balanced detector in the next frequency sweep cycle, and After performing a Fourier transform, the frequency corresponding to the upper sweep cycle can be obtained. and the frequency corresponding to the downsweep cycle According to the frequency corresponding to the upper sweep cycle and the frequency corresponding to the downsweep cycle This will give you the target's distance and speed.

[0029] However, in practical applications, when the target is moving at a high speed or is very close, i.e. , middle, The variable of the function is a negative number (negative frequency), such as -1MHz. However, in the real world, there are only positive frequencies (there is a concept of negative frequency in mathematics, but in reality, only positive frequencies are discussed, and negative frequencies are the mirror image of positive frequencies). Therefore, -1MHz will alias to +1MHz. That is, Doppler frequency shift may cause signal spectrum aliasing, which will lead to errors in distance and velocity measurement results. This aliasing phenomenon not only reduces the measurement accuracy, but may also lead to incorrect target identification and tracking in complex scenarios.

[0030] To address the aliasing problem, several technologies have offered solutions. Some technologies utilize electro-optic IQ modulators (in-phase and quadrature-phase modulators) in lidar transmitters to achieve complex optical field modulation with carrier suppression. However, these technologies suffer from high system complexity, requiring complex and expensive arbitrary waveform generators and IQ modulators, as well as high-bandwidth analog-to-digital converters and complex digital signal processing. Other technologies introduce an optical frequency shift generated by an acousto-optic modulator into the probe light, converting the beat frequency signal to a higher frequency to avoid signal aliasing caused by high-frequency Doppler shift. This allows for direct extraction of distance and velocity information and identification of motion direction through single-pass fast Fourier transform analysis. While this approach offers the advantage of structural simplicity, the frequency shift of the acousto-optic modulator increases the bandwidth of the analog-to-digital converter, raising system costs. Still other technologies enable the emitted FMCW laser to have multiple slopes, overcoming aliasing through complex demodulation methods during signal processing. However, these technologies also suffer from high system design and signal processing complexity.

[0031] Therefore, current technologies for solving the spectral aliasing problem suffer from high system design complexity, high signal processing complexity, and high system cost.

[0032] To address the aforementioned problems, this invention provides a non-aliasing frequency-modulated continuous wave radar detection system and method, which solves the spectral aliasing problem using a simple signal processing approach and system.

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] refer to Figure 1 This invention provides a non-aliasing frequency-modulated continuous wave radar detection system, comprising: a light source 10 for emitting detection light; a beam splitter 20 for splitting the detection light into a local oscillator beam LO and a transmitted beam TX; a circulator 30 for transmitting the transmitted beam TX after passing through the circulator 30, and for reflecting the transmitted beam TX after passing through the target 40 to form a reflected beam RX, which is received by the circulator 30; a 90-degree mixer 50 for interfering the local oscillator beam LO and the reflected beam RX to generate orthogonal first and second optical signals; a signal conversion module for converting the first optical signal into a first electrical signal I and the second optical signal into a second electrical signal Q, wherein both the first and second electrical signals I and Q are digital signals; and a signal processing unit 80 configured to: construct a composite vector signal S, S = I + jQ, based on the first electrical signal I and the second electrical signal Q, where j is the imaginary part operator, and obtain a double-sideband spectrum based on the composite vector signal S to determine the frequency of the signal peak within the upper sweep period of the double-sideband spectrum. and the frequency of the signal peak within the lower sweep cycle Based on the frequency of the signal peak within the up-sweep cycle and the frequency of the signal peak within the lower sweep cycle Obtain the distance and speed of the target 40.

[0039] It should be noted that the circulator 30 is used to guide the emitted beam to the target under test and to guide the reflected beam to the receiving part. The beam splitter 20 is used to split the probe beam into a local oscillator beam and an emitted beam. The beam splitting ratio of the beam splitter 20 is not limited. For example, 90% of the probe beam can be used for the emitted beam and 10% of the probe beam can be used for the local oscillator beam. In practical applications, the specific beam splitting ratio can be set according to the detector threshold, detection range, and other conditions.

[0040] In some examples, the probe light emitted by the light source 10 is an FMCW laser, specifically a sawtooth wave modulated laser whose frequency varies linearly with time. The method by which the light source 10 generates the FMCW laser can include predistortion driving or optical phase-locked loop, etc.

[0041] In some examples, the non-aliasing frequency-modulated continuous wave radar detection system may also include a collimator and / or a scanning device. The collimator is used to collimate the detection beam, and the scanning device is used to scan and image the detection beam. The scanning device may be at least one of a mechanical rotating mirror, a MEMS mirror, a piezoelectric mirror, or an optical phased array chip.

[0042] Furthermore, the probe light is a triangular-wavelength frequency-modulated continuous-wave laser, and the electric field of the probe light during the upper frequency sweep period... and the electric field of the probe light during the lower frequency sweep period Satisfy the following expression:

[0043] ;in, The initial optical frequency, t is the linear frequency modulation rate, T is the period of the triangular wave, and t is time.

[0044] Furthermore, the electric field of the emitted beam during the upper frequency sweep period and the electric field of the emitted beam during the lower frequency sweep period Satisfy the following expression:

[0045] ;in, Let be the electric field amplitude of the emitted beam.

[0046] Electric field of the local oscillator beam during the upper frequency sweep period The electric field of the local oscillator beam during the lower sweep frequency period Satisfy the following expression:

[0047] ;in, The amplitude of the electric field of the local oscillator beam is denoted as .

[0048] The reflected beam has a flight time interval. Therefore, a delay is generated relative to the local oscillator beam, and the electric field of the reflected beam during the upper frequency sweep period is affected. The electric field of the reflected beam during the lower frequency sweep period as follows:

[0049] ;in, The amplitude of the reflected light beam. This refers to the flight time interval.

[0050] Furthermore, the first optical signal includes two first signals with opposite phases, and the second optical signal includes two second signals with opposite phases. The light intensities of the two first signals with opposite phases are I1(t) and I2(t), respectively, and the light intensities of the two second signals with opposite phases are I3(t) and I4(t), respectively.

[0051] ,in, The Doppler frequency shift is the frequency shift caused by the motion of the target object, and t is time. For flight time intervals, For linear frequency modulation rate, and When the sign between them is -, it represents the up-sweep cycle. and When the sign between the two is +, it represents the downsweep frequency period.

[0052] The derivation of I1(t), I2(t), I3(t), and I4(t) is as follows: The reflected beam and the local oscillator beam interfere in the 90-degree mixer 50. During the up-sweep period, the optical field expressions of the optical signals corresponding to the four output ports of the 90-degree mixer 50 are as follows:

[0053] ;

[0054] The above formula can be further extended to:

[0055] ;

[0056] Where cc represents complex conjugate and j is the imaginary number symbol.

[0057] Similarly, during the next frequency sweep cycle, the optical field expressions for the optical signals corresponding to the four output ports of the 90-degree mixer 50 are as follows:

[0058] ;

[0059] The above formula can be further extended to:

[0060] ;

[0061] Where cc represents complex conjugate and j is the imaginary number symbol.

[0062] It should be noted that, This represents the optical field of the first port during the upper frequency sweep period. This represents the optical field at the second port during the upper frequency sweep period. This represents the optical field at the third port during the upper frequency sweep period. This represents the optical field of the fourth port during the upper frequency sweep period. This represents the optical field at the first port during the next frequency sweep period. This represents the optical field at the second port during the next frequency sweep period. This represents the optical field obtained at the third port during the next frequency sweep period. This represents the optical field of the fourth port during the lower frequency sweep period.

[0063] Based on the above optical field expression, the light intensity of each port of the 90-degree mixer 50 during the upper and lower sweep cycles can be obtained. The light intensity of the first port of the 90-degree mixer 50 during the upper sweep cycle is taken as an example. For example, its expression is as follows:

[0064] ;

[0065] in, and These represent the DC quantity of the local oscillator signal and the DC quantity of the reflected signal, respectively. This is the intermediate frequency component obtained after mixing the two frequencies. The DC component is used in subsequent signal processing, where Fourier spectrum analysis is performed. Since the DC component only appears at frequencies of 0, it has no effect on distance and speed analysis. Therefore, for the sake of simplicity, the formula is simplified. The text has been omitted. The amplitude of the intermediate frequency signal determines the signal-to-noise ratio of the system and is independent of the principles of distance and velocity analysis. For the sake of simplicity, this has been omitted. Similarly, the light intensity at the four ports of the 90-degree mixer can be obtained. , , as well as .

[0066] Furthermore, the signal conversion module includes a photodetector 60 and an analog-to-digital converter 70. The photodetector 60 converts the first optical signal into a first analog electrical signal and converts the second optical signal into a second analog electrical signal.

[0067] Among them, the photodetector 60 is a balanced detector. The material of the balanced detector can be silicon or indium gallium arsenide. This invention does not limit the material of the balanced detector. A suitable balanced detector material can be selected according to the system operating wavelength and noise requirements.

[0068] Furthermore, the expressions for the first analog electrical signal I(t) and the second analog electrical signal Q(t) are as follows:

[0069] Where R is the responsivity of photodetector 60. The Doppler frequency shift is the motion of the target object 40, where t is time. For flight time intervals, For linear frequency modulation rate, T is the triangular wave period of the probe light, and BW is the linear frequency modulation bandwidth.

[0070] It should be noted that since the cosine function is an even function, i.e., cos(-x) = cos(x), where x represents a variable, according to the expressions for the first analog electrical signal I(t) and the second analog electrical signal Q(t), if the target's speed is too fast or the distance is too close (e.g., in a scenario where an autonomous vehicle detects a pedestrian at close range), then... The original frequency was The frequency of the cosine signal will be aliased. ,Right now Frequency aliasing will lead to errors in ranging and speed measurement.

[0071] Furthermore, the analog-to-digital converter 70 converts the first analog electrical signal into a first electrical signal I, and converts the second analog electrical signal into a second electrical signal Q. It should be noted that the first electrical signal I is sampled by one analog-to-digital converter, and the second signal Q is sampled by another analog-to-digital converter.

[0072] Furthermore, composite vector signals , and When the sign between them is -, it represents the up-sweep cycle. and When the sign between the two is +, it represents the downsweep frequency period.

[0073] Furthermore, the signal processing unit 80 obtains the double-sideband spectrum based on the composite vector signal S by performing a fast Fourier transform on the composite vector signal to obtain the double-sideband spectrum.

[0074] Furthermore, the signal processing unit 80 uses the frequency of the signal peak within the up-sweep period of the double-sideband spectrum. and the frequency of the signal peak within the lower sweep cycle Obtaining the distance and velocity of the target 40 includes: obtaining the distance and velocity of the target 40 based on Formula 1, as follows:

[0075] Where d is the distance to the target 40, v is the velocity of the target 40, T is the triangular wave period of the probe light, BW is the linear frequency modulation bandwidth, λ is the wavelength of the probe light, and c is the speed of light.

[0076] In some embodiments, the specific methods for constructing a composite vector signal and performing a fast Fourier transform to obtain a double-sideband spectrum include the following.

[0077] The first method uses Matlab's FFT function for signal processing. Specifically, the data of the first electrical signal I and the second electrical signal Q are imported into Matlab software. A composite vector signal S is constructed using addition operations, and then, according to Euler's formula... The composite vector signal S is subjected to a Fast Fourier Transform (FFT) using Matlab's FFT function to obtain a double-sideband spectrum. Within this spectrum, the max function is used to find the frequencies of the signal peaks within the upper and lower sweep periods, respectively. and Then, calculate the distance and speed of the target under test according to the aforementioned Formula 1.

[0078] The second method uses the same approach as the first to obtain the composite vector signal S. Then, the double-sideband spectrum is calculated using the following formula. ,in, Let N be the k-th element of the composite vector signal, and N be the sampling length. Given the k-th element of the spectral signal, after obtaining the double-sideband spectrum, find the frequency of the signal peak within the upper and lower sweep cycles, i.e. and Then, calculate the distance and speed of the target under test according to the aforementioned Formula 1.

[0079] The third method also uses FPGA (Field Programmable Gate Array) chips and ASIC (Application Specific Integrated Circuit) chips to calculate the double-sideband spectrum. Taking the FFT IP (Intellectual Property Core) of the FPGA chip as an example, the sampled I and Q values ​​are input into the real and imaginary parts of the IP core, respectively. After several clock cycles, the output interface of the IP core will output the spectrum one by one at the clock rate. The method for finding the signal peak is as follows: when the IP core starts outputting the spectrum, a counter is started synchronously. The counter data increments with the clock, and the counter value represents the frequency value. The spectrum value output by the IP core is connected to a register. After each new element is output, it is compared with the value in the register. If the newly output spectrum value is larger, the counter register stores the current counter value; otherwise, the original value is maintained. After the IP core has finished calculating the spectrum, the frequency position of the signal peak can be obtained.

[0080] This invention provides, in another aspect, a non-aliasing frequency-modulated continuous wave radar detection method. This method is based on the aforementioned non-aliasing frequency-modulated continuous wave radar detection system and includes: emitting detection light using a light source 10; splitting the detection light into a local oscillator beam and a transmitted beam using a beam splitter 20; emitting the transmitted beam through a circulator 30 and reflecting it off the target 40 to form a reflected beam; receiving the reflected beam using the circulator 30; interfering the local oscillator beam and the reflected beam using a 90-degree mixer 50 to generate orthogonal first and second optical signals; converting the first optical signal into a first electrical signal I and the second optical signal into a second electrical signal Q using a signal conversion module, where both the first and second electrical signals I and Q are digital signals; and constructing a composite vector signal S, S = I + jQ, based on the first and second electrical signals Q using a signal processing unit 80, where j is the imaginary part operator, and obtaining the double-sideband spectrum based on the composite vector signal S to determine the frequency of the signal peak within the upper sweep period of the double-sideband spectrum. and the frequency of the signal peak within the lower sweep cycle Based on the frequency of the signal peak within the up-sweep cycle and the frequency of the signal peak within the lower sweep cycle Obtain the distance and speed of the target 40.

[0081] The non-aliasing frequency-modulated continuous wave radar detection system and method provided by this invention solves the signal aliasing problem in high-speed or close-range target detection, and improves detection accuracy and reliability.

[0082] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0083] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A frequency-modulated continuous wave radar detection system without aliasing, characterized in that, include: A light source, which is used to emit detection light; A beam splitter splits the probe light into a local oscillator beam and an emitted beam. A circulator, through which the emitted light beam is emitted, and after being reflected by the target to be measured, the emitted light beam is reflected to form a reflected light beam, which is received by the circulator; A 90-degree mixer is used to generate orthogonal first and second optical signals by interference between the local oscillator beam and the reflected beam. The signal conversion module converts the first optical signal into a first electrical signal I and the second optical signal into a second electrical signal Q, wherein both the first electrical signal I and the second electrical signal Q are digital signals. The signal processing unit is configured to: construct a composite vector signal S, S = I + jQ, based on the first electrical signal I and the second electrical signal Q, where j is the imaginary part operator; the composite vector signal , and When the sign between them is -, it represents the up-sweep cycle. and When the sign is +, it represents the lower sweep period. The double-sideband spectrum is obtained based on the composite vector signal S, and the frequency of the signal peak within the upper sweep period in the double-sideband spectrum is determined. and the frequency of the signal peak within the lower sweep cycle Based on the frequency of the signal peak within the up-sweep cycle and the frequency of the signal peak within the lower sweep cycle Obtain the distance and velocity of the target to be measured; The signal processing unit obtains the double-sideband spectrum based on the composite vector signal S by performing a fast Fourier transform on the composite vector signal to obtain the double-sideband spectrum. The signal processing unit is based on the frequency of the signal peaks within the up-sweep period of the double-band spectrum. and the frequency of the signal peak within the lower sweep cycle Obtaining the distance and velocity of the target to be measured includes: obtaining the distance and velocity of the target to be measured based on Formula 1, wherein Formula 1 is as follows: ； Where d is the distance to the target, v is the velocity of the target, T is the triangular wave period of the probe light, BW is the linear frequency modulation bandwidth, λ is the wavelength of the probe light, and c is the speed of light.

2. The non-aliasing frequency-modulated continuous wave radar detection system according to claim 1, characterized in that, The signal conversion module includes a photodetector and an analog-to-digital converter. The photodetector converts the first optical signal into a first analog electrical signal and the second optical signal into a second analog electrical signal. The analog-to-digital converter converts the first analog electrical signal into a first electrical signal I and the second analog electrical signal into a second electrical signal Q.

3. The non-aliasing frequency-modulated continuous wave radar detection system according to claim 2, characterized in that, The expressions for the first analog electrical signal I(t) and the second analog electrical signal Q(t) are as follows: ； Where R is the responsivity of the photodetector. The Doppler frequency shift is the frequency shift caused by the motion of the target object, and t is time. For flight time intervals, For linear frequency modulation rate, T is the triangular wave period of the probe light, and BW is the linear frequency modulation bandwidth.

4. The non-aliasing frequency-modulated continuous wave radar detection system according to claim 1, characterized in that, The first optical signal includes two first signals with opposite phases, and the second optical signal includes two second signals with opposite phases. The light intensities of the two first signals with opposite phases are I1(t) and I2(t), and the light intensities of the two second signals with opposite phases are I3(t) and I4(t). ， in, The Doppler frequency shift is the frequency shift caused by the motion of the target object, and t is time. For flight time intervals, It is a linear frequency modulation rate.

5. The non-aliasing frequency-modulated continuous wave radar detection system according to claim 1, characterized in that, The probe light is a triangular-wavelength frequency-modulated continuous-wave laser. The electric field of the probe light during the upper frequency sweep period and the electric field of the probe light during the lower frequency sweep period Satisfy the following expression: ； in, The initial optical frequency, t is the linear frequency modulation rate, T is the period of the triangular wave, and t is time.

6. The non-aliasing frequency-modulated continuous wave radar detection system according to claim 4, characterized in that, The electric field of the emitted beam during the upper frequency sweep period and the electric field of the emitted beam during the lower frequency sweep period Satisfy the following expression: ； in, The electric field amplitude of the emitted beam; The electric field of the local oscillator beam during the upper frequency sweep period and the electric field of the local oscillator beam during the lower frequency sweep period Satisfy the following expression: ； in, The electric field amplitude of the local oscillator beam; The electric field of the reflected beam during the upper frequency sweep period and the electric field of the reflected beam during the lower frequency sweep period as follows: ； in, The amplitude of the reflected light beam. This refers to the flight time interval.

7. A non-aliasing frequency-modulated continuous wave radar detection method, characterized in that, The non-aliasing frequency-modulated continuous wave radar detection method is implemented based on the non-aliasing frequency-modulated continuous wave radar detection system according to any one of claims 1 to 6, and the non-aliasing frequency-modulated continuous wave radar detection method includes: A probe light is emitted using a light source. The probe light is split into a local oscillator beam and an emitted beam using a beam splitter. The emitted beam is emitted through a circulator and reflected by the target to be measured to form a reflected beam. The reflected beam is received by the circulator. The local oscillator beam and the reflected beam are interfered using a 90-degree mixer to generate orthogonal first and second optical signals; The signal conversion module is used to convert the first optical signal into a first electrical signal I and the second optical signal into a second electrical signal Q, where both the first electrical signal I and the second electrical signal Q are digital signals. A signal processing unit constructs a composite vector signal S, S = I + jQ, based on the first electrical signal I and the second electrical signal Q, where j is the imaginary part operator. The double-sideband spectrum is then obtained based on the composite vector signal S, and the frequency of the signal peak within the upper sweep period of the double-sideband spectrum is determined. and the frequency of the signal peak within the lower sweep cycle Based on the frequency of the signal peak within the upper sweep cycle and the frequency of the signal peak within the lower sweep cycle Obtain the distance and speed of the target to be tested.

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