CN108957412A - Radar detection and method for communication transmission based on piece-wise linear FM signal - Google Patents

Abstract

The invention discloses a kind of radar detection based on piece-wise linear FM signal and method for communication transmission, solving reduces radar data reduction after radar signal modulation communication data and the problem of shared signal is unfavorable for Linear Amplifer.Specific steps have: radar communication data prediction；Piece-wise linear FM signal parameter is set；Generate piece-wise linear FM signal；Emit and receives pulse-modulated signal；The distance and speed of detection radar target；Demodulate radar communication data.The present invention devises the piece-wise linear FM signal with permanent envelope and fixed-bandwidth, does data modulation to middle section linear FM signal time width and frequency modulation polarity, it is made to carry the communication information, becomes the shared signal that can be detected target and transmit data.The present invention overcomes there is range ambiguity with normal pulsed signal detection, solving communications and radar detection occupies the contradiction of power, transmission is more acurrate, and the bit error rate is lower, in radar-communication integration system.

Description

Radar Detection and Communication Transmission Method Based on Segmented Chirp Signal

technical field

The invention belongs to the technical field of radar, and further relates to detection and communication transmission in radar communication, in particular to a method for radar detection and communication transmission based on segmented chirp signals. It is used in radar communication integrated system.

Background technique

In order to adapt to the development of information technology in the future, airborne and shipborne platforms reflect the "informatization advantage", which requires the development and use of platforms to have a systematic trend, so that various airborne platforms can realize cross-domain and over-distance communication through electronic information channels. Collaborate in real time. At the same time, in order to adapt to the requirements of the modern information environment, the airborne platform needs to be equipped with a large number of electronic equipment such as radar, communication equipment, etc. The comprehensive performance of electrical equipment is affected. If the communication function can be added to the radar equipment to make it run as a system, and a radar communication sharing signal is designed, the comprehensive utilization rate of electronic equipment will be greatly improved.

Li Xiaobai, Yang Ruijuan, Chen Xinyong et al. proposed a linear-based The initial frequency modulation communication information of the frequency modulation signal (Chirp) realizes the method of radar communication integration. In this method, different initial frequencies of Chirp signals are used to modulate user data, and the transmission of multi-bit information of a single Chirp signal is achieved. Its disadvantage is that the communication data demodulation process is not robust to Doppler, and under the same bandwidth condition, the spectrum efficiency of communication is low, it is difficult to meet the transmission of large quantities of data in wartime, and the initial frequency Demodulation method for modulated information.

Xidian University has proposed a multi-carrier chirp signal in its patent "A method for realizing radar detection and communication transmission based on chirp signal" (application number 201710028374, publication number 106772350A). Frequency modulation communication data overcomes the problem that the traditional technology modulates the communication data on the radar signal to reduce the radar detection target distance and speed performance, and the data demodulation process is not robust to Doppler. However, the multi-carrier LFM shared signal is controlled by the main carrier Superimposed with the subcarrier, the main carrier is used for radar detection, and the subcarrier is used for the same i performance. If the power used for communication increases, the power used for radar detection will decrease, and its communication bandwidth will increase with Modulation data varies, so the multi-carrier form is not conducive to linear amplifier work. That is to say, the existing LMF sharing signal technology has contradictions between communication and radar detection occupying radar transmission power, and there are technical problems that are not conducive to linear amplification.

Contents of the invention

The purpose of the present invention is to maintain the advantages of the existing LMF shared signal technology, overcome its shortcomings, design a method with a constant envelope, which is beneficial to linear amplification based on segmented chirp signals, and realize radar detection and communication transmission.

The present invention is a radar detection and communication transmission method based on a segmented chirp signal, which is characterized in that it includes the following steps:

(1) Radar communication data preprocessing: serial-to-parallel conversion and grouping of the communication data to be sent to obtain several arrays to be transmitted with N-bit binary numbers;

(2) Construct a segmented chirp signal generator, and set the segmented chirp signal initialization parameters:

The input of the segmented chirp signal generator is the array to be transmitted, and the output is a three-segment chirp signal with a continuous time-frequency relationship. The three-segment chirp signal with a continuous time-frequency relationship is recorded as D ₁ segment from left to right , section D ₂ , section D ₃ ; set initialization parameters in the segmented chirp generator, set the center frequency f _c of a chirp signal, the total bandwidth B of the chirp signal and the total time width τ of the chirp wave 1. A time width library containing chirp signals with equal intervals of 2 ^M-1 time widths, M represents the number of binary data sent by each pulse, M is equal to N, and the time is aligned according to the position of the time width in the time width library The width is numbered in decimal numbers, and the number m corresponds to the binary data group;

(3) Generate a segmented linear frequency modulation (PLFM) signal: input the array to be transmitted into the segmented linear frequency modulation signal generator, generate a segmented linear frequency modulation signal according to the array to be transmitted and the segmented linear frequency modulation signal model, and Transmitting the signal as a reference signal to a matched filter in the radar detection processing module;

(4) Transmit pulse modulation signal: input the segmental linear frequency modulation signal to the pulse modulator at the same time, generate the segmental linear frequency modulation signal after pulse modulation, referred to as the pulse modulation signal, and input the pulse modulation signal into the radar transmitter, and transmit the pulse modulation signal;

(5) Receiving the echo signal: the radar receiver receives the echo, and inputs the echo of the segmental chirp signal into the radar detection processing module and the radar communication data demodulation processing module respectively;

(6) Detecting the distance and speed of the radar target: the radar detection processing module first inputs the echo signal of the received segmental chirp signal to the matched filter for pulse compression processing to obtain the distance of the radar target, and then compresses the pulse The processed signal is input to the Doppler filter bank for moving target detection MTD processing to obtain the speed of the radar target;

(7) Demodulate to obtain radar communication data: while the radar detection processing module is working, that is, while obtaining the calculation process of the distance and speed of the radar target, demodulate to obtain the communication carried in the echo signal of the segmented chirp signal data.

The present invention designs a segmented linear frequency modulation signal, which is used in an integrated radar communication system. On the premise of not reducing the radar detection performance, the same system can be used to realize the transmission of radar communication data.

Compared with prior art, the present invention has following advantage:

First, the PLFM shared signal designed by the present invention is a constant envelope signal and has a constant communication bandwidth, thereby overcoming the disadvantages of the prior art that are not conducive to linear amplifiers.

Second, because the present invention uses the currently transmitted FM signal as the reference signal of the matched filter, and performs pulse compression processing with the received echo, the matched filter in the present invention changes with the modulated radar communication data , thus solving the distance ambiguity problem that would exist in ordinary pulse signals.

Third, because the present invention adopts segmented chirp signals, it overcomes the disadvantage of the prior art that there is a contradiction between the occupied power of communication transmission and the occupied power of radar detection.

Fourth, the present invention uses a segmented linear frequency modulation signal as a shared signal, which has constant bandwidth, time width and center frequency, and thus has good correlation, thereby overcoming the problem of modulating radar communication data in radar detection signals in the prior art Finally, the detection resolution of the radar target is reduced, so that the present invention improves the performance of the radar detection target distance and speed. And by setting the bandwidth of the D ₁ segment and D ₃ segment LFM signal in the segmented linear frequency modulation (PLFM) shared signal, better range resolution or lower first side lobe can be obtained, further improving the performance of the radar.

The 5th, because what the present invention adopts is to carry out fractional order Fourier transform processing to echo, has overcome the unsteadiness of Doppler in the demodulation process of radar communication data in the prior art, and causes bit error rate to increase The problem of solving the problem makes the transmission of radar communication data more accurate and the bit error rate lower in the present invention, thereby completing the transmission of single-pulse multi-bit data.

Description of drawings

Fig. 1 is a flow chart of the present invention;

Fig. 2 is the simulation figure of pulse compression processing result of the present invention;

Fig. 3 is the simulation diagram of the processing result of moving target detection MTD of the present invention;

Fig. 4 is a simulation diagram of fractional Fourier transform results of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings.

Example 1

The airborne platform needs to be equipped with a large number of electronic equipment such as radar and communication equipment, but these equipment not only occupy valuable space in the platform, increase its load, and deteriorate the surrounding electromagnetic environment, but also affect the overall performance of avionics equipment, such as airborne radar Detection and communication use their own transmitters. In the prior art, there is a contradiction between communication and radar detection occupying radar transmission power, and it is not conducive to linear amplification work. The present invention explores and researches this situation, and proposes a segmented The radar detection and communication transmission method of chirp signal, referring to Fig. 1, includes the following steps:

(1) Radar communication data preprocessing: serial-to-parallel conversion and grouping of the communication data to be sent to obtain several arrays to be transmitted with N-bit binary numbers;

(1a) The radar transmitter divides the radar communication serial data to be transmitted into multiple arrays, and each array has N binary data;

(1b) Input the grouped serial data into the serial-to-parallel converter, convert it into parallel data, and obtain the data group to be transmitted.

(2) Construct a segmented chirp signal generator, and set the segmented chirp signal initialization parameters:

The input of the segmented chirp signal generator is an array to be transmitted, and the output is a three-segment chirp signal with a continuous time-frequency relationship. The three-segment chirp signal with a continuous time-frequency relationship is recorded as D ₁ , D ₂ , D ₃ , the three-segment chirp signal with continuous time-frequency relationship is constructed with a segmented chirp signal model, that is, the three segments are D ₁ segment, D ₂ segment, and D ₃ segment.

Set the initialization parameters in the segmented chirp generator, set the center frequency f _c of a chirp signal, the total bandwidth B of the chirp signal and the total time width τ of the chirp wave, a 2 ^M- The time width library of the chirp signal with ¹ time width, M represents the number of binary data sent by each pulse, M is equal to N, the time width is numbered in decimal numbers according to the position of the time width in the time width library, and The number m corresponds to the binary data group, and the number is stored in the segmented chirp generator. The function of the segmented chirp generator is to generate the corresponding segmented chirp signal waveform according to the segmented chirp signal model .

The invention constructs a segmented linear frequency modulation generator, and the function of the segmented linear frequency modulation generator is to generate a corresponding segmented linear frequency modulation signal waveform according to a known segmental linear frequency modulation signal model.

(3) Generate a segmented linear frequency modulation (PLFM) signal: input the array to be transmitted into the segmented linear frequency modulation signal generator, generate a segmented linear frequency modulation signal according to the array to be transmitted and the segmented linear frequency modulation signal model, and The signal is transmitted as a reference signal to the matched filter in the radar detection processing module to participate in pulse compression processing.

(4) Transmit pulse modulation signal: when the reference signal is passed into the matched filter, the segmented linear frequency modulation signal is input to the pulse modulator to generate a segmented linear frequency modulation signal after pulse modulation, referred to as the pulse modulation signal. A pulse-modulated signal is input into the radar transmitter, and the pulse-modulated signal is transmitted.

(5) Receiving the echo signal: the radar receiver receives the echo, and inputs the echo of the segmental chirp signal into the radar detection processing module and the radar communication data demodulation processing module respectively. In the integrated radar communication system, The radar detection processing module is a module used for radar detection and detection in the system, and generally includes matched filters, Doppler filters and other components. The radar communication data demodulation processing module is a module used to demodulate and obtain radar communication data in the system.

(6) Detecting the distance and speed of the radar target: the radar detection processing module first inputs the echo signal of the received segmental chirp signal to the matched filter for pulse compression processing to obtain the distance of the radar target, and then compresses the pulse The processed signal is input to the Doppler filter bank for moving target detection MTD processing to obtain the velocity of the radar target.

(7) Demodulate to obtain radar communication data: while the radar detection processing module is working, that is, while obtaining the calculation process of the distance and speed of the radar target, demodulate to obtain the communication carried in the echo signal of the segmented chirp signal data.

Using the present invention can increase the communication function on the radar equipment, make the airborne radar detection and communication become an integrated system, make it run as one system, and use the same transmitter for detection and communication, which will greatly improve the comprehensive utilization rate of electronic equipment, And when the data is modulated for the radar detection signal, it can maintain good radar detection performance.

Example 2

The radar detection and communication transmission method of segmented chirp signal is the same as embodiment 1, and the generation of segmented chirp (PLFM) signal described in step 3 includes the following steps:

(3a) Input the array to be transmitted to the segmented chirp signal generator.

(3b) Determine the positive or negative of the D ₂ -segment modulation frequency according to the lowest binary number of the array to be transmitted, and the calculation formula is as follows:

Wherein, a represents the binary value of the lowest bit of the array to be sent, and sign (a) represents the polarity of D ₂ -segment modulation frequency; the array to be sent is the array to be transmitted, and the present invention only needs to calculate the positive and negative of the middle section D ₂ -segment modulation frequency .

(3c) Select the time width corresponding to the binary number of the high (N-1) bit of the array to be transmitted as the time width of the P ₂ -segment signal, and calculate the time of the D ₁ and D ₃ -segment chirp signals by the time width calculation formula Width, time width calculation formula is:

δ _τ = (τ-τ _m )/2

Among them, τ _m represents the selected D ₂ -segment time width, m represents the number of the D ₂ -segment time width, τ represents the total time width of the segmented chirp signal, and δ _τ is the duration of D ₁ -segment and D ₃ -segment width.

(3d) Calculate the modulation frequency of the three segments of the linear frequency modulation signal respectively, and the modulation frequency of each segment signal is calculated by the following calculation formula:

Among them, μ ₁ , μ ₂ , and μ ₃ represent the frequency modulation frequency of D ₁ -segment, D ₂ -segment, and D ₃ -segment chirp signals, f _c represents the center frequency of the segmented chirp signal, and B represents the segmented chirp The total bandwidth of the signal, δ _B is the bandwidth _of the D1 segment and _D3 segment signal, this variable can be set independently according to user needs.

(3e) Calculate the carrier frequency of the three-segment linear frequency modulation signal, and the carrier frequency of each segment signal is calculated by the following calculation formula:

Among them, f _c represents the center frequency of the segmented chirp signal, f _k represents the carrier frequency of the D _k -segment chirp signal, and k is the subscript of the carrier frequency of each segment chirp signal, which is 1, 2, and 3 in turn.

(3f) According to the calculated parameters, use the segmented chirp signal model to generate a segmented chirp signal, and pass the generated segmented chirp signal into the matched filter as a reference signal, wherein the segmented chirp The model s(t) of the chirp signal is as follows:

Wherein, t represents time, and the calculated parameters include μ ₁ , μ ₂ , μ ₃ , f ₁ , f ₂ , f ₃ , τ _m , τ, δ _τ .

Using this method of generating a segmented chirp signal, a segmented chirp signal can be simply generated, this segmented chirp signal has a constant envelope, which is conducive to the work of linear amplification, because of the communication function and radar radar detection The function is realized with the same signal, so there is no problem of power consumption conflict between the radar detection function and the communication function.

The present invention carries out communication information by performing data modulation on the time width and frequency modulation polarity of the D ₂ -segment LFM signal, and its single pulse can carry multi-bit data, thereby improving the frequency spectrum efficiency of communication.

Example 3

The radar detection and communication transmission method of segmented chirp signal is the same as embodiment 1-2, and the method for demodulating radar communication data described in step 7 includes the following steps:

(7a) Calculate the order of the fractional Fourier transform of the echo, and set the calculated order into the fractional Fourier transform demodulator.

(7b) Carry out fractional Fourier transform of setting orders on the echo, each order obtains the amplitude value on the frequency sampling point, and draws the order corresponding to the amplitude value on the order-frequency-amplitude plane- Frequency-magnitude plot.

(7c) Retrieve the order-dimensional coordinate value of the peak point on the order-frequency-amplitude diagram, select the coordinate with only one peak value from the selected order-dimensional coordinates, and use the coordinate transformation formula μ=-cot(pπ /2) to obtain the frequency modulation frequency of the D ₂ -segment chirp component in the echo, wherein μ represents the frequency modulation frequency of the echo D ₂ -segment chirp signal, cot represents the cotangent operation, and p represents the order dimensional coordinates of the peak point value.

(7d) Calculate and obtain the radar communication data, and store the obtained binary number into the cache array.

(7e) Input the parallel data in the cache array to the parallel-serial converter to convert it into serial communication data, and output the serial communication data.

What the present invention adopts is to carry out fractional-order Fourier transform processing to echo, for PLFM shared signal, communication data is only coded to the modulation frequency of D ₂ section LFM signal, and Doppler frequency shift is to fractional-order Fourier transform processing stage The number has no influence, thereby can overcome the unsteadiness of Doppler in the demodulation process of radar communication data in the prior art, and cause the problem that bit error rate increases, make the transmission of radar communication data of the present invention more accurate, erroneous The code rate is lower, so as to complete the transmission of single pulse multi-bit data.

Example 4

The radar detection and communication transmission method of the segmented chirp signal is the same as embodiment 1-3, and the order of the fractional Fourier transform described in step (7a) is calculated by the following formula:

Among them, p _i represents the order of fractional Fourier transform of the i-th echo, i takes 0,1,...,2 ^K -1 in turn, K represents the number of binary data sent by each pulse, K and N take The same value, arccot represents the inverse cotangent operation, B represents the total bandwidth of the segmented chirp signal, τ _j represents the jth time width in the segmented time width library, when i<2 ^K-1 , j takes 0 ,1,...,2 ^K-1 -1, when i≥2 ^K-1 , j takes 0,1,...,2 ^K-1 -1, π represents the circumference ratio.

The present invention carries out data modulation on the time width and frequency modulation polarity of the D _{2 -} segment LFM signal, so that it carries radar communication information. Linking the orders of leaf transforms makes it possible to implement demodulation using fractional Fourier transforms.

Example 5

The radar detection and communication transmission method based on segmented chirp signal is the same as embodiment 1-4, and the calculation described in step (7d) obtains the radar communication data, including the following steps:

(7d1) A one-bit binary number can be determined according to the positive or negative of the modulation frequency of the D ₂ -segment linear frequency modulation signal in the echo. When the modulation frequency is a positive number, a binary number 1 is obtained, and when the modulation frequency is a negative number, a binary number 0 is obtained. This one-bit binary number is a one-bit binary number in the radar communication data obtained through demodulation.

(7d2) In the time width library, search for the time width equal to the time width value of the D ₂ -segment signal in the echo, each D ₂ -segment LFM time width corresponds to a decimal number, take out the corresponding time width number, and convert the decimal number The serial number is converted into the corresponding binary number to obtain the binary number of N-1 bits, wherein, the time width formula of section D ₂ is calculated by the following formula:

Among them, τ _m represents the time width of the D ₂ -segment chirp signal in the echo, m represents the decimal number of the D ₂ -segment chirp signal duration, μ represents the frequency modulation frequency of the D ₂ -segment chirp signal in the echo, and B represents The total bandwidth of the echo segmented chirp signal, |·| represents the absolute value operator.

(7d3) using the one-bit binary number gained in step (7d1) as the lowest first digit of the radar communication array, and the N-1 bit binary number gained in step (7d2) as the high N-1 bit of the radar communication array, and the obtained binary number The numbers are combined into an array of N-bit binary numbers, which is the radar communication data written in the echo.

As an important step for demodulating the segmented chirp signal and obtaining radar communication data, the present invention uses a look-up table method to obtain radar communication data, which is simple to implement and has a small amount of calculation, which is beneficial to realize the real-time processing of the integrated radar communication system.

A more specific example is given below to further illustrate the present invention

Example 6

The radar detection and communication transmission method based on segmented chirp signal is the same as embodiment 1-5, with reference to Fig. 1, the specific implementation steps of the present invention are as follows:

Step 1, radar communication data preprocessing.

The radar transmitter divides the radar communication serial data to be transmitted into multiple arrays, and each array has N binary data. N represents the number of binary data sent by each pulse, which is determined by the data transmission rate and the pulse repetition period, and is calculated according to the following formula:

N=[L·PRI]

Among them, L represents the data transmission rate, PRI represents the pulse repetition period, [] represents the rounding operation, · represents the dot multiplication operation.

Taking N=3 as an example, group the radar communication serial data 0,1,1,0,1,0,1,0,0,0,0,1,... into [0,1,1] , [0,1,0], [1,0,0], [0,0,1],….

The grouped serial data is input to the serial-to-parallel converter and converted into parallel data to obtain the data groups to be transmitted, [011], [010], [100], [001], ....

Step 2, setting the parameters of the chirp signal.

In the linear frequency modulation signal generator, set the center frequency f _c of a linear frequency modulation signal, the total time width τ and the total bandwidth B, the bandwidth δ _B of the first and third segment signals of the segmented linear frequency modulation signal, a set including, etc. Interval 2 ^M-1 time width segmented chirp signal time width library of the second segment chirp signal, M represents the number of binary data sent by each pulse, M and N take the same value, according to the time width in It is numbered by its position in the time-width library, And satisfy τ _m =τ·m/M, and correspond the number to the binary data group, when N=3, the time width τ ₀ , τ ₁ , τ ₂ , τ ₃ in the time width library are respectively corresponding to 00, 01, 10 , corresponding to 11.

Step 3, generate a segmented chirp signal

Input the data group to be transmitted into the chirp signal generator, select the second segment chirp signal time width corresponding to the number of the upper N-1 digit of the data group, and determine the segmented chirp by the value of the lowest bit of the array The frequency modulation main polarity sign(a) of the signal, the relationship is shown in the following formula:

Among them, a represents the value of the lowest bit of the array. When the array is 011, select the time width τ ₁ , and select positive for the frequency modulation main polarity.

From the center frequency f _c of the set chirp signal, the total time width τ and the total bandwidth B, and the bandwidth δ _B of the first and third segment signals of the segmented chirp signal, the three-segment chirp signal is calculated as follows Center frequency and tuning frequency:

Among them, μ ₁ , μ ₂ , μ ₃ represent the frequency modulation frequencies of the first, second and third segment chirp signals, f _k represents the carrier frequency of the kth segment chirp signal, and f _c , τ, B represent segment The center frequency, total time width and total bandwidth of the linear FM signal, δ _B is the bandwidth of the first and third segment of the linear FM signal, τ _m represents the selected second segment time width, and δ _τ is the first and third segment The duration of the segment is calculated by the formula δ _τ =(τ-τ _m )/2.

The linear frequency modulation signal generator generates segmented linear frequency modulation signal s(t) from the calculated three-segment linear frequency modulation frequency μ ₁ , μ ₂ , μ ₃ and carrier frequency f ₁ , f ₂ , f ₃ , The segmented chirp signal generated is input to the matched filter as the reference signal of the matched filter, and the model of the segmented chirp signal can be expressed as:

Step 4, transmitting and receiving pulse modulation signals.

Input the segmented linear frequency modulation signal to the pulse modulator, modulate it in the pulse with pulse width τ and pulse repetition period PRI, generate pulse modulated multi-carrier linear frequency modulation signal, and input the pulse modulation signal into the radar transmitter , and transmit the pulse-modulated signal.

The radar receiver receives the echo s'(t) of the pulse modulation signal, the echo includes the range delay t ₁ and the Doppler frequency shift f _d of the radar target, and inputs the echo s'(t) into the radar detection processing module and the radar communication data demodulation processing module.

Step 5, detect the distance and speed of the radar target.

The radar detection processing module inputs the received echo to the matched filter, performs pulse compression processing, obtains the amplitude value at the time sampling point, and draws the time-amplitude diagram corresponding to the amplitude value on the time-amplitude plane.

Retrieve the time dimension coordinate value t ₁ of the peak point on the time-amplitude graph, and obtain the distance of the radar target by the coordinate transformation formula R=ct ₁ /2, where R represents the distance of the radar target, c represents the speed of light, and t ₁ represents The time dimension coordinate value of the peak point.

Input the processing result of the matched filter to the Doppler filter bank, do the MTD processing of the moving target, obtain the amplitude value at the time sampling point and the frequency sampling point, and draw the corresponding amplitude value on the time-frequency-amplitude plane Time-frequency-magnitude graph.

Retrieve the frequency dimension coordinate value f _d of the peak point on the time-frequency-amplitude diagram, and obtain the velocity of the radar target by the coordinate transformation formula v=λf _d /2, where v represents the speed of the radar target, and λ represents the pulse modulation signal The wavelength of , f _d represents the frequency dimension coordinate value of the peak point.

Step 6, demodulating the radar communication data.

Calculate the order of the echo fractional Fourier transform according to the following formula, and set the calculated order to the fractional Fourier transform demodulator:

Among them, p _i represents the order of fractional Fourier transform of the i-th echo, i takes 0,1,...,2 ^K -1 in turn, K represents the number of binary data sent by each pulse, K and N take The same value, arccot represents the inverse cotangent operation, B represents the total bandwidth of the segmented chirp signal, τ _j represents the jth time width in the segmented time width library, when i<2 ^K-1 , j takes 0 ,1,...,2 ^K-1 -1, when i≥2 ^K-1 , j takes 0,1,...,2 ^K-1 -1, π represents the circumference ratio.

The radar communication data processing module inputs the received echo into the fractional-order Fourier transform demodulator, performs fractional-order Fourier transform processing on the echo with a set order, and obtains frequency sampling points at each order The amplitude value of , draw the order-frequency-amplitude diagram corresponding to the amplitude value on the order-frequency-amplitude plane.

Retrieve the order dimension coordinate value p of the peak point on the order-frequency-amplitude diagram, and obtain the modulation frequency of the second segment of the chirp signal in the echo by the coordinate transformation formula μ=-cot(pπ/2), wherein, μ represents the modulation frequency of the subcarrier chirp signal component in the echo, cot represents the cotangent operation, and p represents the order-dimensional coordinate value of the peak point.

The lowest bit of the array is determined by the sign of the modulation frequency of the second segment of the linear frequency modulation signal. If it is a positive number, the lowest bit of the array is 1; if it is a negative number, the lowest bit of the array is 0. Calculate the duration of the second chirp signal according to the following formula:

Among them, τ _m represents the time width of the second chirp signal in the echo, μ represents the modulation frequency of the second chirp signal in the echo, and B represents the total bandwidth of the segmented chirp signal in the echo.

From the time-width library of the second segment of the segmented chirp signal, retrieve the time width equal to the time width of the second segment of the chirp signal calculated in the echo, and take out and retrieve from the corresponding relationship in step 2 The radar communication binary number corresponding to the obtained modulation frequency number is used as the high M-1 bit of the array.

Taking N=3 as an example, the frequency modulation frequency of the second segment of the chirp signal is a positive number, the lowest bit of the radar communication array is 1, and the calculated time width is τ ₁ , then the binary number of the upper two bits is 01, and finally combined to obtain The radar communication array is 011.

Input the parallel data in the data group to the serial converter to convert it into serial data, and output the serial data.

In the radar communication integrated system, the present invention utilizes the characteristics of low correlation of chirp signals of different frequency modulation frequencies to design a segmented chirp shared signal with constant envelope and fixed bandwidth, that is, a three-dimensional signal with continuous time-frequency relationship. The segment LFM signal carries communication information through data modulation on the time width and frequency modulation polarity of the second segment LFM signal, and becomes a shared signal capable of detecting targets and transmitting data.

The technical effects of the present invention will be further described in conjunction with simulation experiments.

Example 8

The radar detection and communication transmission method of segmented chirp signal is the same as embodiment 1-7,

Simulation conditions and content:

The processing results of the pulse pressure and MTD of the PLFM shared signal echo of a single target were simulated respectively, among which, the simulation parameters: total bandwidth B=20MHz, total time width τ=10μs, duty cycle 10%, δ _B =0.75B, Target parameter [5000m, 50m/s], because the set δ _B >0.5B, the first side lobe is lower than -13dB. The time-width library [2.5 5.0 7.510.0] μs of segmental chirp signal simulation software environment is Pentium(R) Dual-Core CPU E5200@2.50GHz, Matlab R2010a under Windows 7 32bit operating system.

Each pulse sends 3-bit modulation data, binary modulation data group 000~111, its high two bits correspond to the 4 time widths in the time width library in turn, and its lowest one determines the frequency modulation polarity of the second segment of LFM, such as 011 Select the corresponding frequency modulation as τ ₁ =5.0μs, and the polarity of the main frequency modulation is positive.

Simulation content and result analysis:

Simulation 1: Process the echo to get the distance and velocity of the radar target.

Using the method of the present invention to simulate the pulse-modulated segmented linear frequency modulation signal, adding the distance delay and Doppler frequency shift of the target to the signal to simulate its echo signal, and convoluting the echo with the inverted conjugate signal of the current reference signal The product operation simulates the matched filter, and converts the time dimension coordinates into the distance dimension coordinates. The simulation diagram of the pulse compression processing results is shown in Figure 2. In Figure 2, there is an obvious peak at the abscissa of 5000. The abscissa is the distance dimension, and the ordinate is Corresponding amplitude, it can be seen in the figure that adopting the distance of the detected target of the present invention is 5000 meters, i.e. the coordinate value where the peak is located in Fig. 2, which is consistent with the target distance set in the simulation, which verifies that the present invention has ranging function, thereby It shows that the radar detection performance is not reduced after the radar communication data is modulated.

After performing the MTD simulation processing on the convolution operation results, the obtained data is drawn in a two-dimensional graph. The time dimension coordinates are converted into distance dimension coordinates, and the frequency dimension coordinates are converted into velocity dimension coordinates. The simulation diagram of the moving target detection MTD processing results As shown in Figure 3 and Figure 3, the X-axis represents the distance dimension, the Y-axis represents the velocity dimension, and the Z coordinate represents the corresponding amplitude. It can be seen from Fig. 3 that an obvious peak appears when the velocity dimension coordinate is 50, which is also consistent with the simulation conditions The set speeds are consistent, the peak amplitude is higher, and the side lobe is lower, indicating that the present invention does not reduce the ability of the radar to find targets in the Doppler field after modulating the data.

Simulation 2: Perform fractional Fourier transform on the echo to demodulate the radar communication data.

The 8 orders of the fractional Fourier transform of the echo are calculated from the time-width library of the segmental linear frequency modulation signal, and the echo with a pulse repetition period length is taken, and the fractional Fourier transform is performed eight times, and the data is plotted In the three-dimensional diagram, the order dimensional coordinates are converted into numbered dimensional coordinates. The simulation diagram of the fractional Fourier transform result is shown in Figure 4. It can be seen from Figure 4 that the radar communication data transmitted by the pulse modulation signal is 011, and the completion is completed. Single pulse multi-bit data transmission.

In short, the radar detection and communication transmission method based on the segmented chirp signal disclosed in the present invention solves the problem of reducing the distance and speed performance of the radar detection target after the communication data is modulated on the radar signal in the prior art, and the existing Technical issues that are not conducive to linear scaling. The specific steps include: 1. Radar communication data preprocessing, 2. Setting segmental chirp signal parameters, 3. Generating segmental chirp signal, 4. Transmitting pulse modulation signal, 5. Receiving pulse modulation signal, 7. Detection 7. Demodulate radar communication data. The present invention designs a segmented chirp signal with constant envelope and fixed bandwidth, and performs data modulation on the time width and FM polarity of the second chirp signal, so that it carries communication information and becomes a detectable target and shared signals for transmitting data. While maintaining the advantages of the prior art that the distance and speed performance of the radar detection target is not reduced after the communication data is modulated on the radar signal, the invention overcomes the disadvantage of being unfavorable to linear amplification due to the change of the communication bandwidth. The invention solves the distance ambiguity problem of ordinary pulse signals, overcomes the disadvantages of the prior art that the power occupied by communication transmission and the power occupied by radar detection are contradictory, the transmission is more accurate, the bit error rate is lower, and it is used for radar communication integration System detection and communication transmission.

Claims (5)

1. a kind of radar detection and method for communication transmission based on piece-wise linear FM signal, comprises the following steps that

(1) radar communication data prediction: by communication data serioparallel exchange pending and being grouped, obtain several with the position N two into The array to be transmitted of number processed；

(2) piece-wise linear Wide band Chirp Waveform Generator is constructed, piece-wise linear FM signal initiation parameter: segmented line is set The input of property Wide band Chirp Waveform Generator is array to be transmitted, and output is the continuous three-stage linear FM signal of relationship between frequency and time, when The continuous three-stage linear FM signal of frequency relationship is from left to right successively denoted as D₁、D₂、D₃；

Initiation parameter is set in piece-wise linear Wide band Chirp Waveform Generator, the centre frequency of a linear FM signal is set f_c, linear FM signal total bandwidth B and linear frequency modulation wave total time width τ, one include equally spaced 2^M-1A time width it is linear The time width library of FM signal, M indicate the binary data number that each pulse is sent, and M is equal to N, according to time width in time width library Position time width is numbered with decimal number, and it is number m is corresponding with binary data group；

(3) it generates piece-wise linear frequency modulation (PLFM) signal: array to be transmitted is inputted into piece-wise linear Wide band Chirp Waveform Generator In, piece-wise linear FM signal is generated according to array to be transmitted and piece-wise linear FM signal model, and the signal is made It is reference signal transmission into the matched filter in radar detection processing module；

(4) emit pulse-modulated signal: while piece-wise linear FM signal is input to pulse-modulator, generate impulse modulation Pulse-modulated signal is input in radar transmitter, concurrently by piece-wise linear FM signal afterwards, abbreviation pulse-modulated signal Penetrate the pulse-modulated signal；

(5) receives echo-signal: radar receiver receives echo, and the echo of piece-wise linear FM signal is separately input to thunder Up in detection processing module and radar communication data demodulation processing module；

(6) distance and speed of detection radar target: radar detection processing module first believes the piece-wise linear frequency modulation received Number echo-signal be input to matched filter carry out process of pulse-compression, obtain the distance of radar target, then pulse is compressed Signal input Doppler filter group that treated carries out moving-target detection MTD processing, obtains the speed of radar target；

(7) demodulation obtains radar communication data: while the work of radar detection processing module, that is, obtaining the distance of radar target While with the calculating process of speed, demodulation obtains the communication data carried in the echo-signal of piece-wise linear FM signal.

2. the method according to claim 1 that radar detection and communications are realized based on piece-wise linear FM signal, It is characterized by: generation piece-wise linear frequency modulation (PLFM) signal described in step 3, comprises the following steps that

Array to be transmitted is input to piece-wise linear Wide band Chirp Waveform Generator by (3a)；

(3b) determines D according to the minimum bit of array to be transmitted₂Section frequency modulation rate it is positive and negative, calculation formula is as follows:

Wherein, a indicates that minimum one binary numeral of array to be sent, sign (a) indicate D₂Section adjusts frequency polarity；

(3c) is selected with the time width of the binary number reference numeral of the position the height of array to be transmitted (N-1) as D₂The time width of segment signal, D is calculated by time width calculation formula₁And D₃The time width of section linear FM signal, time width calculation formula are as follows:

δ_τ=(τ-τ_m)/2

Wherein, τ_mIndicate selected D₂Duan Shikuan, m indicate the D₂The number of Duan Shikuan, τ indicate piece-wise linear FM signal Total time width, δ_τFor D₁Section, D₃The time width of section；

(3d) calculates separately the frequency modulation rate of three sections of linear FM signals, and the frequency modulation rate of each segment signal is calculated by following calculation formula It obtains:

Wherein, μ₁、μ₂、μ₃Indicate D₁Section, D₂Section, D₃The frequency modulation rate of section linear FM signal, f_cIndicate piece-wise linear FM signal Centre frequency, B respectively indicate the total bandwidth of piece-wise linear FM signal, δ_BFor D₁Section, D₃The bandwidth of segment signal, the variable It can be independently arranged according to user demand；

(3e) calculates three sections of linear FM signal carrier frequency, and the carrier frequency of each segment signal is calculated by following calculation formula:

Wherein, f_cIndicate the centre frequency of piece-wise linear FM signal, f_kIndicate D_kThe carrier frequency of section linear FM signal, k is each The subscript of the carrier frequency of section linear FM signal, successively takes 1,2,3；

(3f) generates piece-wise linear FM signal according to the parameter being calculated, with piece-wise linear FM signal model, And wherein piece-wise linear frequency modulation letter is passed in matched filter using the piece-wise linear FM signal of generation as reference signal Number model s (t), it is as follows:

Wherein, t indicates the time.

3. the radar detection and method for communication transmission according to claim 1 based on piece-wise linear FM signal, special Sign is that the method that radar communication data are demodulated described in step 7 comprises the following steps that

(7a) calculates the order of echo Fourier Transform of Fractional Order, by the order being calculated setting to Fourier Transform of Fractional Order In demodulator；

(7b) is configured the Fourier Transform of Fractional Order of order to echo, and each order obtains the amplitude on stepped-frequency signal Value, draws order-frequency amplitude diagram corresponding with range value in order-frequency-amplitude plane；

(7c) retrieves the order dimensional coordinate values of peak point on order-frequency amplitude diagram, selects from selected order dimension coordinate The coordinate of only one peak value out obtains D in echo by coordinate transform formula μ=- cot (p pi/2)₂Section linear FM signal point The frequency modulation rate of amount, wherein μ indicates echo D₂The frequency modulation rate of section linear FM signal, cot indicate cotangent operation, and p indicates peak point Order dimensional coordinate values；

Radar communication data are calculated in (7d), and obtained binary number is stored in caching array；

The parallel data cached in array is input to parallel-to-serial converter and is converted into serial communication data by (7e), and by serial communication Data output.

4. the radar detection and method for communication transmission according to claim 3 based on piece-wise linear FM signal, special Sign is that the order of Fourier Transform of Fractional Order described in step (7a) is calculated by following formula:

Wherein, p_iIndicate that the order of i-th of echo Fourier Transform of Fractional Order, i successively take 0,1 ..., 2^K- 1, K indicate each arteries and veins The binary data number sent is rushed, K and N take identical numerical value, and arccot indicates arc cotangent operation, and B indicates piece-wise linear tune The total bandwidth of frequency signal, τ_jJ-th of time width in segmentation time width library is indicated, as i < 2^K-1When, j takes 0,1 ..., and 2^K-1- 1, when i >= 2^K-1When, j takes 0,1 ..., and 2^K-1- 1, π indicate pi.

5. the radar detection and method for communication transmission according to claim 3 based on piece-wise linear FM signal, special Sign is, radar communication data are calculated described in step (7d) and comprise the following steps that

(7d1) is according to the D in echo₂Positive and negative determination 1 binary number of section linear FM signal frequency modulation rate, when frequency modulation rate is When positive number, binary digit 1 is obtained, when frequency modulation rate is negative, obtains binary number 0；

(7d2) retrieval and D in echo in time width library₂The equal segmentation time width of the when width values of segment signal, taking-up are obtained with retrieval Time width number converts corresponding binary number for decimal number number, obtains N-1 binary numbers, wherein D₂Section when What wide formula was calculated by following formula:

Wherein, τ_mIndicate D in echo₂The time width of section linear FM signal, m indicate the D₂The number of section linear FM signal time width, μ indicates D in echo₂The frequency modulation rate of section linear FM signal, B indicate the total bandwidth of echo piece-wise linear FM signal, | | Expression takes absolute value operator.

Obtained binary number is pieced together the radar communication array for having N bit by (7d3), by step (7d1) Minimum first as radar communication array of gained binary number, binary number obtained by step (7d2) is as radar communication number High N-1 of group.