A detection and identification method and system based on frequency modulation and pseudo-random coding

Abstract

The present invention relates to the field of radar communication technology, and discloses a detection and identification method and system based on frequency modulation and pseudo-random coding, wherein the method comprises: the detection device sets waveform parameters, generates and transmits a Chirp signal to a target device through a radar transmitter; the target device performs frequency and phase modulation on the incident Chirp signal through an electromagnetic metasurface, and then reflects the modulated Chirp signal; the detection device uses the Chirp signal obtained by the same modulation method as the target device as a matched filter, performs matched filtering on the received echo signal, calculates the target device code and distance, and realizes radar detection and target identification. The present invention uses an electromagnetic metasurface to make the target passively perform frequency and phase modulation on the incident radar signal, and the detection party can solve the target modulation coding information by knowing the target echo modulation method, thereby identifying the target.

Description

Technical Field

[0001] The present invention relates to the field of radar communication technology, and in particular to a detection and identification method and system based on frequency modulation and pseudo-random coding. Background Art

[0002] In modern information confrontation, radar and communication equipment are the most important information systems, responsible for target detection and information transmission respectively. The two systems generally work independently of each other. The current trend is for equipment platforms to develop from independence to integration. Integrated equipment platforms can reduce loads and costs, and enhance confrontation capabilities. Therefore, it is of practical significance to explore the integrated design of different electronic information systems on equipment platforms.

[0003] At present, the waveform design of the radar communication integration concept can be roughly divided into two categories: one is to combine the radar waveform and the communication waveform into an integrated waveform by using the multiplexing method; the other is to realize the radar detection and communication transmission functions at the same time by redesigning a new single waveform. The multiplexing of radar and communication functions can be achieved based on the orthogonality of one or more dimensions, and radar and communication have independent waveforms respectively. The main characteristics of this type of waveform are: radar and communication waveforms are easy to design, have little impact on each other's performance, and are simple to implement. Currently common waveform multiplexing types include time division multiplexing, space division multiplexing, frequency division multiplexing, and code division multiplexing. The radar communication integration design based on the multiplexing method uses more resources and does not use the design of miniaturized and low-cost systems.

[0004] In order to maximize the use of system resources and adapt to the application scenarios where electromagnetic metasurfaces reflect radar echoes to achieve detection and identification at the same time, a single common waveform can be used to achieve target detection and data transmission functions. According to the different integration methods of radar and communication, the common waveform integration design can be roughly divided into integration based on radar waveforms and integration based on communication waveforms. The radar-based integrated waveform refers to a radar waveform as the main component, on which communication data is modulated. The communication-based integrated waveform refers to a communication waveform as the main component, which is used or transformed into a waveform that can be detected by radar. Given that the electromagnetic metasurface control system is used to modulate radar echoes, the radar communication integrated waveform design for this application scenario should adopt a design method based on radar waveforms. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a detection and identification method and system based on frequency modulation and pseudo-random coding, which can achieve the purpose of reducing equipment load and low cost.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A detection and identification method based on frequency modulation and pseudo-random coding, comprising:

[0008] Radar signal generation and transmission: The detection device sets the waveform parameters, generates and transmits the Chirp signal to the target device through the radar transmitter;

[0009] Radar signal echo modulation: The target device performs frequency and phase modulation on the incident Chirp signal through the electromagnetic metasurface, and then reflects the modulated Chirp signal; the frequency and phase modulation includes frequency coding modulation of the Chirp signal through the frequency modulation step and a number of frequency modulation codes, and BPSK modulation of the frequency coded modulated Chirp signal through pseudo-random coding;

[0010] Radar ranging and target identification: The detection device uses the Chirp signal obtained by the same modulation method as the target device as a matched filter to perform matched filtering on the received echo signal; the matched filtering result is normalized and a threshold is set. The matched filter code corresponding to the peak value above the threshold is the corresponding target device code, and the time domain position corresponding to the peak value indicates the time of receiving the reflected echo from the target device, thereby calculating the target device code and distance to achieve radar detection and target identification.

[0011] Furthermore, in the radar signal echo modulation, the chirp signal is frequency coded modulated by a frequency modulation step and a plurality of frequency modulation codes, including:

[0012] Set the frequency modulation code and superimpose the Chirp signal Different initial frequencies:

[0013]

[0014]

[0015] in, represents Chirp signal, Represents the Chirp signal after frequency coding modulation; Represents a rectangular pulse with a width of T, where T is the period. , , Indicates the sampling time interval; Indicates the carrier frequency; is the linear FM modulation slope, B is the linear FM modulation bandwidth; i Indicates frequency modulation coding, ; represents an imaginary unit; Indicates the frequency modulation step length; ” represents the dot product.

[0016] Furthermore, in the radar signal echo modulation, BPSK modulation is performed on the Chirp signal after frequency coding modulation by pseudo-random coding, including:

[0017] Set the pseudo code sequence of length P , the value is -1 or 1;

[0018] The pseudo code sequence The corresponding baseband signal Expressed as:

[0019]

[0020] Among them, Q represents the pseudo code sequence The number of sampling points for each symbol in , p Indicates p Code elements, q Indicates the first q sampling points, represents a unit impulse signal;

[0021] Use the baseband signal generated by pseudo-random coding to phase modulate the frequency coded modulated Chirp signal:

[0022]

[0023] in, The integrated signal obtained by phase modulation of the pseudo-random code is used as the echo modulation signal.

[0024] Furthermore, the radar ranging and target identification includes:

[0025] The matched filtering method is used to compress and demodulate the echo signal to construct the echo modulation signal. The conjugate anti-fold signal As a matched filter, it performs matched filtering on the received echo signal:

[0026]

[0027] in, represents the matched filtering result, Indicates mixed echo, represents the y-th matched filter, ” indicates convolution; N represents the number of electromagnetic metasurface targets, Represents the autocorrelation function of the target signal and the transmitted signal; represents Gaussian white noise; when When the matched filtering result is at position The target peak appears at is the echo delay of different targets; when When , the target peak will not appear in the matched filtering result, thus the frequency modulation code corresponding to the target echo can be screened out;

[0028] According to the matched filtering results, find the peak value and record the distance value estimation result at this time And the corresponding matched filter frequency modulation value estimation result .

[0029] A detection and identification system based on frequency modulation and pseudo-random coding, comprising:

[0030] The detection device is configured to generate and transmit a Chirp signal to a target device through a radar transmitter; and use the Chirp signal obtained by the same modulation method as the target device as a matched filter to perform matched filtering on the received echo signal; and normalize the matched filtering result and set a threshold value. The matched filter code corresponding to the peak value above the threshold value is the corresponding target device code, and the time domain position corresponding to the peak value indicates the time of receiving the reflected echo of the target device, thereby calculating the target device code and distance, and realizing radar detection and target identification;

[0031] The target device is configured to perform frequency and phase modulation on the incident Chirp signal through an electromagnetic metasurface, and then reflect the modulated Chirp signal; the frequency and phase modulation includes frequency coding modulation of the Chirp signal through a frequency modulation step and a plurality of frequency modulation codes, and BPSK modulation of the frequency coded modulated Chirp signal through a pseudo-random code.

[0032] Furthermore, the target device performs frequency coding modulation on the Chirp signal through a frequency modulation step and a plurality of frequency modulation codes, including:

[0033] Set the frequency modulation code and superimpose the Chirp signal Different initial frequencies:

[0034]

[0035]

[0036] in, represents Chirp signal, Represents the Chirp signal after frequency coding modulation; Represents a rectangular pulse with a width of T, where T is the period. , , Indicates the sampling time interval; Indicates the carrier frequency; is the linear FM modulation slope, B is the linear FM modulation bandwidth;i Indicates frequency modulation coding, ; represents an imaginary unit; Indicates the frequency modulation step length; ” represents the dot product.

[0037] Furthermore, the target device performs BPSK modulation on the frequency coded modulated Chirp signal through pseudo-random coding, including:

[0038] Set the pseudo code sequence of length P , the value is -1 or 1;

[0039] The pseudo code sequence The corresponding baseband signal Expressed as:

[0040]

[0041] Among them, Q represents the pseudo code sequence The number of sampling points for each symbol in , p Indicates p Code elements, q Indicates the first q sampling points, represents a unit impulse signal;

[0042] Use the baseband signal generated by pseudo-random coding to phase modulate the frequency coded modulated Chirp signal:

[0043]

[0044] in, The integrated signal obtained by phase modulation of the pseudo-random code is used as the echo modulation signal.

[0045] Furthermore, the detection device uses a Chirp signal obtained by the same modulation mode as the target device as a matched filter to perform matched filtering on the received echo signal, including:

[0046] The matched filtering method is used to compress and demodulate the echo signal to construct the echo modulation signal. The conjugate anti-fold signal As a matched filter, it performs matched filtering on the received echo signal:

[0047]

[0048] in, represents the matched filtering result, Indicates mixed echo, represents the y-th matched filter, ” indicates convolution; N represents the number of electromagnetic metasurface targets, Represents the autocorrelation function of the target signal and the transmitted signal; represents Gaussian white noise; when When the matched filtering result is at position The target peak appears at is the echo delay of different targets; when When , the target peak will not appear in the matched filtering result, thus the frequency modulation code corresponding to the target echo can be screened out;

[0049] According to the matched filtering results, find the peak value and record the distance value estimation result at this time And the corresponding matched filter frequency modulation value estimation result .

[0050] The beneficial effects of the present invention are:

[0051] The present invention uses an electromagnetic metasurface to modulate the frequency and phase of the incident radar Chirp signal before reflecting it, uses frequency modulation to carry code element information, and uses the BPSK method to perform pseudo-random phase modulation on the Chirp signal. The present invention utilizes the good autocorrelation and encryption characteristics of pseudo-random codes, so that the detection equipment can identify our targets and detect the target distance, and can confuse enemy detection equipment. Different frequency modulation codes can be used to number our targets, enriching the recognition function.

[0052] The present invention is different from the existing mode of transmitting and receiving integrated radar communication signals at the same time. Instead, the electromagnetic metasurface is used to make the target passively modulate the frequency and phase of the incident radar signal. If the detection party knows the modulation mode of the target echo, the target modulation coding information can be decoded, thereby achieving the function of identifying the target. If the modulation mode of the unknown radar echo is not only unable to decode the communication information in the echo, but also makes the normal detection function of the radar invalid, which has a confusing interference effect on the non-cooperative radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is one of the flow charts of a detection and identification method based on frequency modulation and pseudo-random coding in Example 1 of the present invention.

[0054] Figure 2 This is the second flow chart of a detection and identification method based on frequency modulation and pseudo-random coding in Example 1 of the present invention.

[0055] Figure 3 This is one of the schematic diagrams of the matched filtering results of the received signal in Example 1 of the present invention.

[0056] Figure 4This is the second schematic diagram of the matched filtering result of the received signal of Example 1 of the present invention.

[0057] Figure 5 This is a schematic diagram of a detection and identification system based on frequency modulation and pseudo-random coding according to Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0058] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0059] Example 1

[0060] like Figure 1 As shown, this embodiment provides a detection and identification method based on frequency modulation and pseudo-random coding, including:

[0061] Radar signal generation and transmission: The detection device sets the waveform parameters, generates and transmits a chirp signal (a signal whose frequency changes over time) to the target device through the radar transmitter;

[0062] Radar signal echo modulation: The target device performs frequency and phase modulation on the incident Chirp signal through the electromagnetic metasurface, and then reflects the modulated Chirp signal; frequency and phase modulation includes frequency coding modulation of the Chirp signal through the frequency modulation step and several frequency modulation codes, and BPSK modulation (i.e. binary phase shift keying modulation) of the frequency coded modulated Chirp signal through pseudo-random coding;

[0063] Radar ranging and target identification: The detection device uses the Chirp signal obtained by the same modulation method as the target device as a matched filter to perform matched filtering on the received echo signal; the matched filtering result is normalized and a threshold is set. The matched filter code corresponding to the peak value above the threshold is the corresponding target device code, and the time domain position corresponding to the peak value indicates the time of receiving the reflected echo from the target device, thereby calculating the target device code and distance to achieve radar detection and target identification.

[0064] like Figure 2 As shown, the detection and identification method of this embodiment can be implemented by the following steps:

[0065] S1. Set waveform parameters to generate a transmitting wave Chirp signal;

[0066] S2. Set frequency modulation coding, mix different target chirp signal echoes with different initial frequencies, and use pseudo-random coding for BPSK modulation;

[0067] S3. Using the conjugate anti-fold signal of the transmitted signal in step S2 as a matched filter, matching filtering is performed on the received echo signal;

[0068] S4. Determine the distance and frequency modulation coding information of the target according to the matched filter peak;

[0069] S5. Repeat step S4 using matched filters carrying different modulation rates until all matched filters complete filtering.

[0070] Preferably, step S2 specifically includes the following sub-steps:

[0071] S201. Set FM coding and superimpose Chirp signal Different initial frequencies:

[0072]

[0073]

[0074] in, represents Chirp signal, Represents the Chirp signal after frequency coding modulation; Represents a rectangular pulse with a width of T, where T is the period. , , Indicates the sampling time interval; Indicates the carrier frequency; is the linear FM modulation slope, B is the linear FM modulation bandwidth; i Indicates frequency modulation coding, ; represents an imaginary unit; Indicates the frequency modulation step length; ” represents the dot product.

[0075] S202. Set the pseudo code sequence of length P , the value is -1 or 1; the pseudo code sequence The corresponding baseband signal Expressed as:

[0076]

[0077] Among them, Q represents the pseudo code sequence The number of sampling points for each symbol in , p Indicates p Code elements, qIndicates the first q sampling points, Represents a unit impulse signal.

[0078] S203. Phase modulation of the frequency coded modulated Chirp signal using a baseband signal generated by pseudo-random coding:

[0079]

[0080] in, The integrated signal obtained by phase modulation of the pseudo-random code is used as the echo modulation signal.

[0081] It should be noted that the echo signal of a normal target is , L is the distance to the target, Tao is the echo delay of different targets. The reflected echo signal of the electromagnetic metasurface target is , if there are 10 electromagnetic metasurface targets, the received mixed echo expression is , is the channel noise, which is set as Gaussian white noise in the experiment.

[0082] Preferably, step S4 specifically includes the following sub-steps:

[0083] S401. In order to maximize the output signal-to-noise ratio and better separate the target echoes with different codes, the matched filtering method is used to perform pulse compression and demodulation on the echo signal to construct the echo modulation signal. The conjugate anti-fold signal As a matched filter, and perform matched filtering on the received echo signal:

[0084]

[0085] in, represents the matched filtering result, Indicates mixed echo, represents the y-th matched filter, ” indicates convolution; N represents the number of electromagnetic metasurface targets, Represents the autocorrelation function of the target signal and the transmitted signal; represents Gaussian white noise; when When the matched filtering result is at position The target peak appears at is the echo delay of different targets; when When , the target peak will not appear in the matched filtering result, thus the frequency modulation code corresponding to the target echo can be screened out;

[0086] S402. According to the matched filtering result, the peak value is found. The horizontal axis corresponding to the peak value represents the reflection wave time. It can be converted into the distance of the target and the estimated distance value at this time is recorded. And the corresponding matched filter frequency modulation value estimation result The experimental matched filtering results are as follows: Figure 3 and Figure 4 As shown, the matched filtering results of different matched filters on the received echo in a noisy environment are compared. The peaks of the matched filtering results of matched filter 1 and matched filter 2 are at different positions, corresponding to different targets.

[0087] S403. Replace the matched filter with , repeat step S401 and step S402; after the frequency modulation code value carried by the matching filter increases to the threshold M, end this pulse echo ranging process and obtain the recorded target distance information and the carried code information.

[0088] Example 2

[0089] like Figure 5 As shown, this embodiment provides a detection and identification system based on frequency modulation and pseudo-random coding, including:

[0090] The detection device is configured to generate and transmit a Chirp signal to a target device through a radar transmitter; and use the Chirp signal obtained by the same modulation method as the target device as a matched filter to perform matched filtering on the received echo signal; and normalize the matched filtering result and set a threshold value. The matched filter code corresponding to the peak value above the threshold value is the corresponding target device code, and the time domain position corresponding to the peak value indicates the time of receiving the reflected echo of the target device, thereby calculating the target device code and distance, and realizing radar detection and target identification;

[0091] The target device is configured to perform frequency and phase modulation on the incident Chirp signal through the electromagnetic metasurface, and then reflect the modulated Chirp signal; the frequency and phase modulation includes frequency coding modulation of the Chirp signal through the frequency modulation step and a plurality of frequency modulation codes, and BPSK modulation of the frequency coded modulated Chirp signal through pseudo-random coding.

[0092] Preferably, the target device performs frequency coding modulation on the Chirp signal through a frequency modulation step and a plurality of frequency modulation codes, including:

[0093] Set the frequency modulation code and superimpose the Chirp signal Different initial frequencies:

[0094]

[0095]

[0096] in, represents Chirp signal, Represents the Chirp signal after frequency coding modulation; Represents a rectangular pulse with a width of T, where T is the period. , , Indicates the sampling time interval; Indicates the carrier frequency; is the linear FM modulation slope, B is the linear FM modulation bandwidth; i Indicates frequency modulation coding, ; represents an imaginary unit; Indicates the frequency modulation step length; ” represents the dot product.

[0097] Preferably, the target device performs BPSK modulation on the frequency coded modulated Chirp signal through pseudo-random coding, including:

[0098] Set the pseudo code sequence of length P , the value is -1 or 1;

[0099] The pseudo code sequence The corresponding baseband signal Expressed as:

[0100]

[0101] Among them, Q represents the pseudo code sequence The number of sampling points for each code element in , p Indicates p Code elements, q Indicates the first q sampling points, represents a unit impulse signal;

[0102] Use the baseband signal generated by pseudo-random coding to phase modulate the frequency coded modulated Chirp signal:

[0103]

[0104] in, The integrated signal obtained by phase modulation of the pseudo-random code is used as the echo modulation signal.

[0105] Preferably, the detection device uses a Chirp signal obtained by the same modulation mode as the target device as a matched filter to perform matched filtering on the received echo signal, including:

[0106] The matched filtering method is used to compress and demodulate the echo signal to construct the echo modulation signal. The conjugate anti-fold signal As a matched filter, it performs matched filtering on the received echo signal:

[0107]

[0108] in, represents the matched filtering result, Indicates mixed echo, represents the y-th matched filter, ” indicates convolution; N represents the number of electromagnetic metasurface targets, Represents the autocorrelation function of the target signal and the transmitted signal; represents Gaussian white noise; when When the matched filtering result is at position The target peak appears at is the echo delay of different targets; when When , the target peak will not appear in the matched filtering result, thus the frequency modulation code corresponding to the target echo can be screened out;

[0109] According to the matched filtering results, find the peak value and record the distance value estimation result at this time And the corresponding matched filter frequency modulation value estimation result .

[0110] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity of description, they are expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

Claims

1. A detection and identification method based on frequency modulation and pseudo-random coding, characterized in that: include: Radar signal generation and transmission: The detection device sets the waveform parameters, generates and transmits the Chirp signal to the target device through the radar transmitter; Radar signal echo modulation: The target device performs frequency and phase modulation on the incident Chirp signal through the electromagnetic metasurface, and then reflects the modulated Chirp signal; the frequency and phase modulation includes frequency coding mixing modulation of the Chirp signal through the frequency modulation step and a number of frequency modulation codes, and BPSK modulation of the frequency modulated Chirp signal through pseudo-random coding; Radar ranging and target identification: The detection device uses the Chirp signal obtained by the same modulation method as the target device as a matched filter to perform matched filtering on the received echo signal; the matched filtering result is normalized and a threshold is set. The matched filter code corresponding to the peak value above the threshold is the corresponding target device code, and the time domain position corresponding to the peak value indicates the time of receiving the reflected echo from the target device, thereby calculating the target device code and distance to achieve radar detection and target identification.

2. A detection and identification method based on frequency modulation and pseudo-random coding according to claim 1, characterized in that: In the radar signal echo modulation, the chirp signal is frequency coded modulated by a frequency modulation step and a plurality of frequency modulation codes, including: Set the frequency modulation code and superimpose the Chirp signal Different initial frequencies: in, represents Chirp signal, Represents the Chirp signal after frequency coding modulation; Represents a rectangular pulse with a width of T, where T is the period. , , Indicates the sampling time interval; Indicates the carrier frequency; is the linear FM modulation slope, B is the linear FM modulation bandwidth; i Indicates frequency modulation coding, ; represents an imaginary unit; Indicates the frequency modulation step length; ” represents the dot product.

3. A detection and identification method based on frequency modulation and pseudo-random coding according to claim 2, characterized in that: In the radar signal echo modulation, BPSK modulation is performed on the Chirp signal after frequency coding modulation by pseudo-random coding, including: Set the pseudo code sequence of length P , the value is -1 or 1; The pseudo code sequence The corresponding baseband signal Expressed as: Among them, Q represents the pseudo code sequence The number of sampling points for each code element in , p Indicates p Code elements, q Indicates the first q sampling points, represents a unit impulse signal; Use the baseband signal generated by pseudo-random coding to phase modulate the frequency coded modulated Chirp signal: in, The integrated signal obtained by pseudo-random code phase modulation is used as the echo modulation signal; ” represents the dot product.

4. A detection and identification method based on frequency modulation and pseudo-random coding according to claim 3, characterized in that: The radar ranging and target identification include: The matched filtering method is used to compress and demodulate the echo signal to construct the echo modulation signal. The conjugate anti-fold signal As a matched filter, and perform matched filtering on the received echo signal: in, represents the matched filtering result, Indicates mixed echo, represents the y-th matched filter, " ” indicates convolution; N represents the number of electromagnetic metasurface targets, Represents the autocorrelation function of the target signal and the transmitted signal; represents Gaussian white noise; when When the matched filtering result is at position The target peak appears at is the echo delay of different targets; when When , the target peak will not appear in the matched filtering result, thus the frequency modulation code corresponding to the target echo can be screened out; According to the matched filtering results, find the peak value and record the distance value estimation result at this time And the corresponding matched filter frequency modulation value estimation result .

5. A detection and identification system based on frequency modulation and pseudo-random coding, characterized in that: include: The detection device is configured to generate and transmit a Chirp signal to a target device through a radar transmitter; The Chirp signal obtained by the same modulation method as the target device is used as a matched filter to perform matched filtering on the received echo signal; the matched filtering result is normalized and a threshold is set. The matched filter code corresponding to the peak value above the threshold is the corresponding target device code, and the time domain position corresponding to the peak value indicates the time of receiving the reflected echo of the target device, thereby calculating the target device code and distance to achieve radar detection and target recognition; The target device is configured to perform frequency and phase modulation on the incident Chirp signal through an electromagnetic metasurface, and then reflect the modulated Chirp signal; the frequency and phase modulation includes frequency coding modulation of the Chirp signal through a frequency modulation step and a plurality of frequency modulation codes, and BPSK modulation of the frequency coded modulated Chirp signal through a pseudo-random code.

6. A detection and identification system based on frequency modulation and pseudo-random coding according to claim 5, characterized in that: The target device performs frequency coding modulation on the Chirp signal through a frequency modulation step and a plurality of frequency modulation codes, including: Set the frequency modulation code and superimpose the Chirp signal Different initial frequencies: in, represents Chirp signal, Represents the Chirp signal after frequency coding modulation; Represents a rectangular pulse with a width of T, where T is the period. , , Indicates the sampling time interval; Indicates the carrier frequency; is the linear FM modulation slope, B is the linear FM modulation bandwidth; i Indicates frequency modulation coding, ; represents an imaginary unit; Indicates the frequency modulation step length; ” represents the dot product.

7. A detection and identification system based on frequency modulation and pseudo-random coding according to claim 6, characterized in that: The target device performs BPSK modulation on the frequency coded modulated Chirp signal through pseudo-random coding, including: Set the pseudo code sequence of length P , the value is -1 or 1; The pseudo code sequence The corresponding baseband signal Expressed as: Among them, Q represents the pseudo code sequence The number of sampling points for each code element in , p Indicates p Code elements, q Indicates the first q sampling points, represents a unit impulse signal; Use the baseband signal generated by pseudo-random coding to phase modulate the frequency coded modulated Chirp signal: in, The integrated signal obtained by phase modulation of the pseudo-random code is used as the echo modulation signal.

8. A detection and identification system based on frequency modulation and pseudo-random coding according to claim 7, characterized in that: The detection device uses a Chirp signal obtained by the same modulation mode as the target device as a matched filter to perform matched filtering on the received echo signal, including: The matched filtering method is used to compress and demodulate the echo signal to construct the echo modulation signal. The conjugate anti-fold signal As a matched filter, and perform matched filtering on the received echo signal: in, represents the matched filtering result, Indicates mixed echo, represents the y-th matched filter, " ” indicates convolution; N represents the number of electromagnetic metasurface targets, Represents the autocorrelation function of the target signal and the transmitted signal; represents Gaussian white noise; when When the matched filtering result is at position The target peak appears at is the echo delay of different targets; when When , the target peak will not appear in the matched filtering result, thus the frequency modulation code corresponding to the target echo can be screened out; According to the matched filtering results, find the peak value and record the distance value estimation result at this time And the corresponding matched filter frequency modulation value estimation result .

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