CN107872279B - Radar communication shared signal design method based on orthogonal frequency decomposition - Google Patents
Radar communication shared signal design method based on orthogonal frequency decomposition Download PDFInfo
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Abstract
The invention discloses a radar communication shared signal design method based on orthogonal frequency decomposition, which solves the problems of large envelope fluctuation of radar communication shared signals, poor fuzzy function performance, high error rate and low transmission rate in the prior art. The implementation steps comprise: setting frequency modulation signal parameters; preprocessing radar communication data; generating a radar communication shared signal with a constant envelope; transmitting and receiving a pulse modulated signal; detecting the distance and speed of the radar target; and demodulating the radar communication shared signal with the constant envelope. The invention designs a high-speed constant-envelope radar communication shared signal, and the signal carries communication information by modulating each base coefficient in an orthogonal system, and realizes a radar detection function. The problems that the signal fuzzy function performance is reduced after communication data are modulated, the error rate is high in the data demodulation process, and the Doppler is not stable in the traditional technology are solved. The method improves the fuzzy function performance of the signal, reduces the error rate, and is used for the multifunctional integration of an electronic equipment system.
Description
Technical Field
The invention belongs to the technical field of radars, particularly relates to a design method of radar communication shared signals, and particularly relates to a design method of radar communication shared signals based on orthogonal frequency decomposition.
Background
Modern radar countermeasures have been transformed from traditional single countermeasures to systematic countermeasures, requiring a multi-task, multi-functional capability of the combat platform. The combat platform needs to be equipped with more and more radars, communication devices and other devices, but a large number of electronic devices not only occupy a large amount of space and increase the reflection area, but also deteriorate the electromagnetic environment of the platform and influence the comprehensive performance of the platform. An effective way to solve the above problems is to implement multifunctional and comprehensive integration of the electronic equipment system, i.e. to implement radar communication function sharing by using a shared signal.
For designing a radar communication shared signal, the existing method mainly focuses on two aspects, namely modulating a radar waveform and designing the radar communication shared signal based on multiple carriers.
Firstly, the method comprises the following steps: starting from a radar waveform, the radar waveform is modulated to be different in different pulse intermediates, and the difference is used for carrying communication information: (1) the method comprises the steps that parameters such as initial frequency, modulation frequency and the like of an LFM signal are modulated, but the communication rate is limited by the pulse repetition period of a radar signal and the number of communication information mapping bits, and the number of FRFT converters at a communication receiving end is increased rapidly due to the excessively high number of bits, so that the communication demodulation efficiency is reduced; (2) the LFM and the constant envelope digital modulation are combined, but the generated radar communication shared signal has the advantages of lower duty ratio of a transmitted signal, shorter pulse width and limited modulation data amount in the PD radar, and the spectrum is seriously expanded along with the increase of the number of modulation code elements, so that the error rate of a communication subsystem is higher, the pulse pressure gain of the radar subsystem is reduced, the detection performance is reduced, and the speed is relatively lower.
II, secondly: the radar communication integration based on the multiple carriers mainly comprises the integration of frequency modulation LFM multiple carriers and OFDM communication signals, and the performances of signal design, processing and the like are mainly researched. However, each carrier in the multi-carrier system has its own amplitude and phase, and after being superimposed, the multi-carrier system generates a large envelope peak-to-average ratio, which causes envelope fluctuation, affects the performance of a class C amplifier at the end of a radar, and reduces the power range of a radar subsystem.
At present, a radar communication shared signal in the prior art is to modulate a radar waveform, but a single carrier system causes the communication demodulation efficiency to be reduced, and a higher bit error rate is generated; and secondly, the radar communication shared signal design based on multiple carriers is adopted, but the multiple carrier system can generate envelope fluctuation, and the influence is generated on the power range of the radar.
Disclosure of Invention
The invention aims to provide a high-speed constant-envelope radar communication shared signal design method based on orthogonal frequency decomposition aiming at the defects of the prior art.
The invention relates to a radar communication shared signal design method based on orthogonal frequency decomposition, which is characterized by comprising the following steps:
(1) generating a frequency modulation signal: setting a center frequency of a frequency modulation signal in a frequency modulation signal generator, and generating the frequency modulation signal;
(2) preprocessing radar communication data: grouping serial communication data to be transmitted, and performing serial-to-parallel conversion according to groups after grouping to obtain parallel communication data to be transmitted;
(3) generating a radar communication shared signal with a constant envelope: carrying out orthogonal frequency decomposition on the frequency modulation signal to obtain a group of orthogonal bases, carrying out group-based modulation on the parallel communication data to be transmitted and the group of orthogonal bases to obtain a radar communication shared signal with constant envelope, wherein the shared signal realizes multi-bit data modulation in a single pulse, is a single carrier system, and is input into a matched filter to be used as a reference signal of the matched filter; according to the designed radar communication shared signal with the constant envelope, the self-fuzzy function of the radar communication shared signal with the constant envelope is obtained through the self-fuzzy function definition, and the self-fuzzy function can be used for analyzing the resolution of the radar communication shared signal with the constant envelope;
(4) transmitting and receiving pulse modulated signals: the radar antenna transmits a radar communication shared signal with constant envelope to a space and receives an echo signal of a target;
(5) range and velocity of the detected radar target: performing pulse compression and moving target detection processing on the echo signal of the target to obtain the distance and the speed of the radar target and finish the radar detection process;
(6) demodulating a constant-envelope radar communication shared signal: extracting the phase of the echo signal from the target echo signal received in the step (4), demodulating parallel code element data from a phase derivative, performing corresponding group-by-group parallel-serial conversion on the parallel code element data to obtain demodulated serial code element data, and outputting the demodulated serial code element data to finish the radar communication process.
The invention realizes high-speed data transmission under the condition of small fluctuation or even no fluctuation of a single carrier envelope, and has excellent radar performance and communication demodulation performance.
Compared with the prior art, the invention has the following advantages:
first, in the multi-carrier system, each carrier has its own amplitude and phase, and after superposition, a large envelope peak-to-average ratio is generated, which causes an envelope fluctuation.
Secondly, the invention adopts the idea of orthogonal diversity, the time-frequency function of any frequency modulation waveform can be decomposed into a group of linear combination of orthogonal systems, and the orthogonal systems are enabled to carry communication information by modulating each base coefficient. The invention has more accurate transmission of radar communication data and lower error rate, thereby completing the transmission of single-pulse multi-bit data.
Thirdly, the serial-to-parallel converted communication information binary data in the invention is modulated by each orthogonal base, and the orthogonal base is designed to have larger degree of freedom, and the larger degree of freedom corresponds to a larger transmission rate.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a graph of a self-ambiguity function simulation of a constant-envelope radar communication share signal generated by the present invention;
FIG. 3 is a simulation plot of a zero Doppler slice of the self-ambiguity function of a constant envelope radar communication share signal generated by the present invention;
FIG. 4 is a simulation diagram of a zero-delay slice of a self-ambiguity function of a constant-envelope radar communication shared signal generated by the present invention;
fig. 5 is a graph of bit error rate versus signal-to-noise ratio for a constant-envelope radar communication sharing signal generated by the present invention under different modulation orders.
Detailed Description
The present invention is described in detail below with reference to the attached drawings.
Example 1
Most radar signals are determined to be of known waveforms, and radar communication signals are random due to modulation of communication information, so that how to realize compatibility of the radar signals and the radar communication signals in a radar system is a difficult point and a demand point. The existing method can not realize high-speed transmission of data under the condition that the single carrier envelope fluctuation is small or even does not fluctuate. The existing method can not enable the radar communication shared signal to have excellent fuzzy function performance and communication demodulation performance. The invention develops research for the purpose, and provides a radar communication shared signal design method based on orthogonal frequency decomposition, which is shown in figure 1 and comprises the following steps:
(1) generating a frequency modulation signal: in the FM signal generator, a center frequency of a FM signal is set, and a FM signal y (t) is generated, and in step (3), quadrature decomposition is performed. The frequency can be arbitrarily selected within the range allowed by the radar operation, but only the frequency modulation signal can be selected.
(2) Preprocessing radar communication data: the serial communication data to be transmitted are grouped, mapped into serial symbol sequences at a transmitting end, and then converted into M parallel symbol sequences every N serial symbol sequences, namely into parallel communication data anThe parallel symbol sequence is modulated into a frequency modulated signal in step (3). In this example, N is 32, and it should be noted that the number of orthogonal bases of orthogonal decomposition in step (3) after the present invention needs to be uniform for every N serial symbol sequences.
(3) Generating a radar communication shared signal with a constant envelope: and (2) carrying out orthogonal frequency decomposition on the frequency modulation signal generated in the step (1) to obtain a group of N orthogonal bases, introducing phase orthogonal diversity, wherein N is 32, and the orthogonal bases are Chebyshev orthogonal bases. And (3) modulating the parallel symbol sequence to be transmitted in the step (2) and the obtained group of orthogonal bases according to a group, wherein the phase is the phase combination of a plurality of orthogonal frequency modulations, and obtaining a radar communication shared signal s (t) with constant envelope, wherein the shared signal realizes multi-bit data modulation in a single pulse and is a single carrier system. And inputting the radar communication shared signal with constant envelope into the matched filter as a reference signal of the matched filter. And obtaining a fuzzy function of the radar communication shared signal with the constant envelope according to the definition of the self-fuzzy function, and analyzing the resolution performance of the fuzzy function.
Because only one frequency modulation signal is modulated, namely a single carrier system is adopted, the problem of envelope fluctuation when a multi-carrier system is adopted to generate the radar communication shared signal is effectively solved. Therefore, the binary data of the communication information after serial-parallel conversion is modulated by each orthogonal basis, the communication transmission rate can be improved, and the radar communication shared signal is not fluctuated and has good radar performance.
(4) Transmitting and receiving pulse modulated signals: and (4) inputting the constant-envelope radar communication sharing signal generated in the step (3) into a pulse modulator by the radar antenna, generating a pulse-modulated constant-envelope radar communication sharing signal, inputting the pulse-modulated constant-envelope radar communication sharing signal into a radar transmitter, and transmitting the pulse-modulated constant-envelope radar communication sharing signal into a space. The radar receiver receives the echo of the pulse modulation signal, and the echo includes information such as the distance and the speed of the radar target.
(5) Range and velocity of the detected radar target: and (4) the radar signal processing module performs pulse compression processing and moving target detection processing on the echo signal of the target received in the step (4), so that the distance and speed information of the radar target can be obtained, and the radar detection process is completed.
(6) Demodulating a constant-envelope radar communication shared signal: and (4) inputting the echo signal obtained in the step (4) into a radar communication data demodulation module, extracting the phase of the echo signal, demodulating a parallel data sequence from a phase derivative, performing corresponding parallel-to-serial conversion on the parallel data sequence according to groups to obtain a serial data sequence, namely demodulated serial communication data, and outputting the demodulated serial communication data to finish the radar communication process. And comparing the demodulated serial communication data with the serial communication data to be transmitted to obtain the proportion of the error code element in the total code element, namely the error rate, and the demodulation performance of the radar communication shared signal with the constant envelope can be seen through the error rate.
The invention adopts a single carrier system, can still obtain excellent fuzzy function performance under the condition of small envelope fluctuation, has low bit error rate under low signal-to-noise ratio and has high transmission rate. Meanwhile, the detection and communication functions of the radar are realized, the equipment utilization rate is effectively improved, the radar communication function sharing is realized in the same platform, and the method has important significance for realizing the multifunctional and comprehensive integration of electronic equipment.
Example 2
The method for designing the radar communication shared signal based on orthogonal frequency decomposition includes the following steps as described in the step (3) of the embodiment 1 to generate the radar communication shared signal with constant envelope
(3a) Orthogonal decomposition is carried out on the frequency modulation signals y (t) generated in the step (1) to obtain a group of orthogonal bases y' (t),
wherein T represents the pulse width, k is the total number of orthogonal bases, l is an orthogonal base variable, and l is more than or equal to 1 and less than or equal to k. The orthogonal base is also called an orthogonal base function, in this example, k is 64, and the orthogonal base is a trigonometric orthogonal base.
(3b) The parallel communication data a generated in the step (2) is processednModulating with orthogonal base to obtain frequency orthogonal modulation item
(3c) Generating a radar communication shared signal with a constant envelope: integrating the frequency quadrature modulation term to obtain a phase modulation term
Therefore, the final radar communication shared signal s (t) with constant envelope of the invention can be obtained, and the expression is as follows:
wherein, betalFor modulating information, betal＝alT/l, j is an imaginary number symbol, the shared signal realizes multi-bit data modulation in a single pulse, and the shared signal is a single carrier system. From the expression of the radar communication shared signal, it can be seen that every K channelsThe serial-to-parallel converted data streams are modulated by different orthogonal bases with a phase that is a linear combination of a plurality of sinusoidal modulation frequencies. Because the degree of freedom of the trigonometric series is large, the transmission rate can reach the required value by increasing the degree of freedom K.
(3d) According to the radar communication shared signal with the constant envelope, the self-fuzzy function of the radar communication shared signal with the constant envelope is generated by using the definition of the self-fuzzy function, and the formula is as follows:
and obtaining a self-fuzzy function χ tau, υ of the radar communication sharing signal with constant envelope, and conveniently carrying out resolution analysis on the radar communication sharing signal with constant envelope.
The orthogonal basis functions selected by the invention need to meet the following requirements: 1. each orthogonal basis needs to be a real number term; 2. each orthogonal basis exhibits orthogonality in the inner product space; 3. the orthogonal subspaces have as many degrees of freedom as possible within an affordable range.
Example 3
The method for designing the radar communication shared signal based on orthogonal frequency decomposition is the same as that in the embodiment 1-2, and the step (6) of demodulating the radar communication shared signal with the constant envelope specifically comprises the following steps
(6a) After receiving the target echo signal, the radar receiver transmits the echo signal to an amplitude-phase receiver, and extracts the phase information of the signal
And the phase is derived to obtain
(6b) The obtained phase derivative
Multiplied by the corresponding orthogonal basis in the set,
and integrating to obtain parallel communication data an，
Where m (x) is a modulation coefficient, and n is the number of an orthogonal base used for demodulation. In this example k is 64
(6c) The obtained parallel communication data anAnd inputting the data into a parallel-serial converter to be converted into demodulated serial communication data, and outputting the demodulated serial communication data to finish the radar communication process.
(6d) And comparing the demodulated serial communication data with the serial communication data to be transmitted to obtain the proportion of the error code element in the total code element, namely the error rate of the radar communication shared signal with constant envelope, so that the demodulation performance of the radar communication shared signal with constant envelope can be conveniently analyzed.
In the prior art, the number of communication information mapping bits is too high, so that the number of FRFT converters at a communication receiving end is increased rapidly, and demodulation efficiency is reduced. In the invention, one communication code element is demodulated through each orthogonal base, and the high-speed effective demodulation of signals can be realized by utilizing parallel processing at a communication receiving end.
Example 4
The method for designing the radar communication shared signal based on the orthogonal frequency decomposition is the same as the embodiments 1 to 3, and referring to fig. 1, the method comprises the following steps:
(1) generating a frequency modulation signal:
in a frequency modulated signal generator, a center frequency of a frequency modulated signal is set to generate a frequency modulated signal.
(2) Preprocessing radar communication data:
(2a) radar serial communication data is generated.
(2b) The radar transmitting end divides serial communication data to be transmitted into M arrays, and each array has N binary data. In this example, N is 128
(2c) And inputting the grouped serial communication data into a serial-parallel converter, and converting the serial communication data into parallel communication data according to groups to obtain the parallel communication data to be transmitted.
(3) Generating a constant-envelope radar communication shared signal:
(3a) carrying out orthogonal decomposition on the frequency modulation signal to obtain a group of N orthogonal bases; in this example, N is 128, the orthogonal basis is legendre orthogonal basis,
(3b) selecting an orthogonal basis with the same number as that of the parallel communication data group to modulate the parallel communication data group to obtain a frequency orthogonal modulation item;
(3c) integrating the frequency orthogonal modulation term to obtain a radar communication shared signal s (t) with constant envelope, wherein the expression is
Inputting the radar communication shared signal with constant envelope into a matched filter as a reference signal of the matched filter;
(3d) according to the generated radar communication shared signal with the constant envelope, the self-fuzzy function of the radar communication shared signal with the constant envelope is obtained through the definition of the self-fuzzy function, and the resolution analysis of the radar communication shared signal with the constant envelope is facilitated.
(4) Transmitting and receiving pulse modulated signals:
(4a) inputting the radar communication sharing signal with the constant envelope into a pulse modulator, generating a radar communication sharing signal with the constant envelope after pulse modulation, inputting the radar communication sharing signal into a radar transmitter, and transmitting the radar communication sharing signal into space.
(4b) The radar receiver receives an echo signal of the pulse modulated signal.
(5) Range and velocity of the detected radar target:
(5a) and inputting the echo signal to a radar signal processing module.
(5b) And the radar detection processing module inputs the received echo to a matched filter for pulse compression processing to obtain the distance of the radar target.
(5c) And inputting the processing result of the matched filter into a Doppler filter bank, and performing Moving Target Detection (MTD) processing to obtain the speed of the radar target and finish the radar detection process.
(6) Demodulating a constant-envelope radar communication shared signal:
(6a) and inputting the echo into a radar communication data demodulation processing module, extracting the phase of an echo signal, and performing derivation on the phase to obtain a phase derivative.
(6b) And multiplying the phase derivative by the corresponding orthogonal basis in the group, and integrating to obtain demodulated parallel communication data.
(6c) And inputting the obtained parallel communication data into a parallel-serial converter to be converted into demodulated serial communication data, and outputting the demodulated serial communication data to finish the radar communication process.
(6d) And comparing the demodulated serial communication data with the serial communication data to be transmitted to obtain the proportion of the error code element in the total code element, namely the error rate of the radar communication sharing signal with constant envelope.
In fact, in all embodiments of the present invention, step (5) and step (6) are performed in parallel, and the echo signal of the pulse modulation signal received in step (4) is simultaneously input to the radar detection processing module and the radar communication data demodulation module.
When designing a radar communication shared signal, how to ensure that the signal realizes high-speed transmission of data under the condition that the single carrier envelope fluctuation is small or even does not fluctuate is a problem which needs to be considered in a key way, and the radar communication shared signal also has excellent fuzzy function performance and communication demodulation performance. The invention orthogonally decomposes the time-frequency function of the frequency modulation signal, introduces orthogonal diversity, and the communication information binary data after serial-parallel conversion is modulated by the corresponding orthogonal base, and the orthogonal base has larger freedom degree by designing the orthogonal base of the frequency modulation function, and the large freedom degree corresponds to large transmission rate, thereby realizing high-speed transmission of the data. In the above embodiments, three orthogonal bases such as chebyshev orthogonal base, trigonometric orthogonal base, legendre orthogonal base, etc. are used, but in practical application, the present invention is not limited to these three orthogonal bases, and any orthogonal base may be used as long as it satisfies the condition for selecting the orthogonal base.
A more complete and thorough example is provided below to further illustrate the present invention
Example 5
The method for designing the radar communication shared signal based on the orthogonal frequency decomposition is the same as the embodiments 1-4, referring to fig. 1, and the specific implementation steps of the invention are as follows:
step 1, setting frequency modulation signal parameters:
in the signal generator, a center frequency f of a frequency-modulated signal is setcThe number of symbols K to be modulated, and the pulse width T.
Step 2, preprocessing radar communication data:
the radar transmitting end divides the radar communication serial data to be transmitted into a plurality of arrays, and each array has N binary data. N represents the number of binary data transmitted by each pulse, and is determined by the data transmission rate and the pulse repetition period, and is calculated according to the following formula:
L＝[N·PRI]
where L denotes a data transmission rate, PRI denotes a pulse repetition period, and [ ] denotes a rounding operation.
Taking N as an example, radar communication serial data 0,1,1,0,1,0,1,0,0,0,0,1, … to be transmitted are grouped into [0,1,1], [0,1,0], [1,0,0], [0,0,1], ….
The grouped serial data is input to a serial-parallel converter to be converted into parallel data, and a data group, [011], [010], [100], [001], … to be transmitted is obtained.
And 3, generating a radar communication sharing signal with constant envelope.
Orthogonally decomposing the generated frequency modulation signal y (t) to obtain an orthogonal base
In this example, k is 3, and the orthogonal base is a trigonometric orthogonal base. The data a generated in the step (2) are processednModulating with orthogonal base to obtain frequency orthogonal modulation item
Integrating the frequency quadrature modulation term to obtain a phase modulation term
Finally obtainRadar communication shared signal to constant envelope
Wherein the modulation information is contained in betalIn, betal＝alAnd T/l. The self-fuzzy function of the radar communication shared signal with the constant envelope is obtained by utilizing the definition of the self-fuzzy function, and the resolution characteristic of the radar communication shared signal with the constant envelope can be obtained by analyzing the self-fuzzy function.
And 4, transmitting and receiving the pulse modulation signal.
Inputting the radar communication shared signal with constant envelope into a pulse modulator, modulating the radar communication shared signal with constant envelope in a pulse with the pulse width tau and the pulse repetition period PRI, generating the radar communication shared signal with constant envelope after pulse modulation, inputting the pulse modulation signal into a radar transmitter, and transmitting the pulse modulation signal.
The radar receiver receives an echo s' (t) of the pulse modulation signal, wherein the echo comprises a distance time delay t of a radar target1And Doppler shift fdAnd respectively inputting the echo s' (t) into a radar signal processing module and a radar communication data demodulation processing module.
And 5, detecting the distance and the speed of the radar target.
And the radar signal processing module inputs the received echo to a matched filter, performs pulse compression processing to obtain an amplitude value on a time sampling point, and draws a time-amplitude graph corresponding to the amplitude value on a time-amplitude plane.
Retrieving a time dimension coordinate value t of a peak point on a time-amplitude plot1From the coordinate transformation formula R ═ ct1(ii)/2, obtaining the distance of the radar target, wherein R represents the distance of the radar target, c represents the speed of light, t1A time dimension coordinate value representing a peak point.
And inputting the processing result of the matched filter into a Doppler filter bank, performing Moving Target Detection (MTD) processing to obtain a time sampling point and an amplitude value on a frequency sampling point, and drawing a time-frequency-amplitude graph corresponding to the amplitude value on a time-frequency-amplitude plane.
Retrieving a frequency dimension coordinate value f of a peak point on a time-frequency-amplitude plotdFrom the coordinate transformation formula v ═ λ fdAnd/2, obtaining the speed of the radar target, wherein v represents the speed of the radar target, lambda represents the wavelength of the pulse modulation signal, and fdA frequency dimension coordinate value representing a peak point.
And 6, demodulating the radar communication shared signal with the constant envelope.
After receiving the echo signal, the radar antenna inputs the echo signal into a radar communication data demodulation processing module, and extracts phase information of the signal
And the phase is differentiated, multiplied by the orthogonal basis corresponding to each order and integrated to obtain a corresponding modulation coefficient, and the modulation coefficient is mapped according to a corresponding mapping relation to obtain parallel communication data. And inputting the obtained parallel communication data into a parallel-serial converter to be converted into demodulated serial communication data, and outputting the serial communication data to finish the radar communication process. The demodulated serial communication data and the serial communication data to be transmitted are compared to obtain the proportion of error code elements in the total code elements, namely the error rate of the radar communication sharing signals with constant envelopes.
The invention adopts the idea of orthogonal diversity, the time-frequency function of any frequency modulation waveform can be decomposed into a group of linear combination of orthogonal systems, and the orthogonal systems are enabled to carry communication information by modulating each base coefficient in the orthogonal systems. The invention has more accurate transmission of radar communication data and lower error rate, thereby completing the transmission of single-pulse multi-bit data.
The technical effects of the present invention will be described below with reference to simulation experiments.
Example 6
Radar communication shared signal design method based on orthogonal frequency decomposition as in embodiments 1-5
Simulation conditions are as follows:
center frequency f of frequency-modulated signalc10GHz, the number of modulated symbols K128, the pulse width τ 10 μ s, the signal bandwidth B100 MHz, and the signal sampling frequency fs＝400MHz。
Simulation content and result analysis:
simulation 1: the self-fuzzy function of the constant envelope radar communication shared signal generated by the invention is used for simulating the resolution performance of the constant envelope radar communication shared signal constructed by the invention.
The method of the invention is utilized to generate the radar communication sharing signal with constant envelope, and the self-fuzzy function of the radar communication sharing signal with constant envelope is drawn by the definition of the fuzzy function, as shown in figure 2, wherein the X-axis coordinate is a time delay sampling unit, the Y-axis coordinate is a Doppler sampling unit, and the Z-axis coordinate is amplitude. The self-blurring function is subjected to corresponding zero doppler slicing as shown in fig. 3, where the abscissa is the delay sampling unit and the ordinate is the amplitude. The self-blurring function is zero-delay sliced as shown in fig. 4, where the abscissa is the doppler sample unit and the ordinate is the amplitude.
As can be seen from fig. 2, the self-fuzzy function of the constant envelope radar communication shared signal designed by the present invention has a pin-shaped protrusion in the center of the image surface, which shows that the constant envelope radar communication shared signal designed by the present invention has a two-dimensional high resolution capability of range-doppler.
As can be seen from fig. 3, the side lobe of the zero doppler slice of the self-ambiguity function of the constant envelope radar communication shared signal designed by the present invention is below-25 dB, which indicates that the constant envelope radar communication shared signal designed by the present invention can obtain excellent performance of high resolution and low side lobe when the pulse pressure method is used for ranging.
As can be seen from fig. 4, the zero-delay slice of the self-ambiguity function of the constant envelope radar communication shared signal designed by the present invention has the same shape as the LFM signal, and is a Sinc function shape, which indicates that the constant envelope radar communication shared signal designed by the present invention also has a high resolution capability in the doppler dimension.
In the radar communication integrated system, the orthogonal diversity idea is utilized, the frequency modulation item of the shared signal is formed by the linear combination of orthogonal function systems, and the communication information modulation is realized by modulating the coefficients of all the bases. The generated shared signal can realize high-speed transmission of data in a single pulse; the fuzzy function has excellent performance; the envelope does not fluctuate. The radar detection and communication transmission can be better realized.
Example 7
The design method of radar communication shared signal based on orthogonal frequency decomposition is the same as that of embodiments 1-5, and the simulation parameters are the same as that of embodiment 6
Simulation 2: the error rate of the radar communication shared signal of the constant envelope generated by the invention is used for simulating the communication performance of the radar communication shared signal of the constant envelope constructed by the invention.
The method of the invention is utilized to generate the radar communication sharing signal with constant envelope, and the curve of the error rate of the radar communication sharing signal with constant envelope along with the change of the signal-to-noise ratio under different modulation orders can be obtained through simulation, as shown in fig. 5, wherein the abscissa is the signal-to-noise ratio and the ordinate is the error rate. The simulation conditions include three symbol parameters, K128, K256, and K1024.
It can be seen from fig. 5 that at different modulation symbol counts the performance is poor at low signal to noise ratio. When the modulation symbol number K is 256 and the SNR is 5dB, the error rate is 10-4The designed shared signal has excellent communication transmission performance. As the number of modulation symbols increases, the error rate performance deteriorates. Because the radar transmission power is far greater than the communication transmission power and the communication process is single-pass attenuation, a high signal-to-noise ratio can be obtained at a communication receiving end. Compared with the bit error rate curve shown in fig. 5, the performance is better under high signal-to-noise ratio, which shows that the signal can effectively realize the communication function of the integrated system.
In summary, the method for designing the high-speed constant-envelope radar communication shared signal provided by the invention realizes energy sharing of an electronic equipment system, and solves the problems of large envelope fluctuation, poor fuzzy function performance, high error rate and low transmission rate of the radar communication shared signal in the prior art. The method comprises the following specific steps: setting frequency modulation signal parameters; preprocessing radar communication data; generating a radar communication shared signal with a constant envelope; transmitting and receiving a pulse modulated signal; detecting the distance and speed of the radar target; and demodulating the radar communication shared signal with the constant envelope. The invention designs a high-speed constant-envelope radar communication shared signal based on orthogonal frequency decomposition, wherein each base coefficient in an orthogonal system is modulated to carry communication information, and radar detection is realized. The problems that the performance of a radar signal fuzzy function is reduced after communication data are modulated on a radar signal in the traditional technology, the error rate is high in the data demodulation process, and the Doppler is not stable are solved. The fuzzy function performance of the signal is improved, and the error rate in the communication process is reduced. The problems that the signal fuzzy function performance is reduced after communication data are modulated, the error rate is high in the data demodulation process, and the Doppler is not stable in the traditional technology are solved. The fuzzy function performance of the signal is improved, the error rate is reduced, and the method has important significance for realizing the comprehensive integration of an electronic equipment system.
The foregoing description is only an example of the present invention and is not intended to limit the invention, so that it will be apparent to those skilled in the art that various changes and modifications in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (3)
1. The method for designing the radar communication shared signal based on orthogonal frequency decomposition is characterized by comprising the following steps of:
(1) generating a frequency modulation signal: setting a center frequency of a frequency modulation signal in a frequency modulation signal generator, and generating the frequency modulation signal;
(2) preprocessing radar communication data: grouping serial communication data to be transmitted, and performing serial-to-parallel conversion according to groups after grouping to obtain parallel communication data to be transmitted;
(3) generating a radar communication shared signal with a constant envelope: carrying out orthogonal frequency decomposition on the frequency modulation signal to obtain a group of orthogonal bases, carrying out group-based modulation on the parallel communication data to be transmitted and the group of orthogonal bases to obtain a radar communication shared signal with constant envelope, wherein the shared signal realizes multi-bit data modulation in a single pulse, is a single carrier system, and is input into a matched filter to be used as a reference signal of the matched filter; according to the designed radar communication shared signal with the constant envelope, the self-fuzzy function of the radar communication shared signal with the constant envelope is obtained through the self-fuzzy function definition, and the self-fuzzy function can be used for analyzing the resolution of the radar communication shared signal with the constant envelope;
(4) transmitting and receiving pulse modulated signals: the radar antenna transmits a radar communication shared signal with constant envelope to a space and receives an echo signal of a target;
(5) range and velocity of the detected radar target: performing pulse compression and moving target detection processing on the echo signal of the target to obtain the distance and the speed of the radar target and finish the radar detection process;
(6) demodulating a constant-envelope radar communication shared signal: extracting the phase of the echo signal from the target echo signal received in the step (4), demodulating parallel code element data from a phase derivative, performing corresponding group-by-group parallel-serial conversion on the parallel code element data to obtain demodulated serial code element data, and outputting the demodulated serial code element data to finish the radar communication process.
2. The method of claim 1, wherein the method comprises: the generating of the radar communication shared signal with the constant envelope in the step (3) specifically includes the following steps:
(3a) carrying out orthogonal decomposition on the frequency modulation signal to obtain a group of N orthogonal bases;
(3b) selecting an orthogonal basis with the same number as that of the parallel communication data group to modulate the parallel communication data group to obtain a frequency orthogonal modulation item;
(3c) integrating the frequency quadrature modulation term to obtain the radar communication share with constant envelopeThe expression of the radar communication shared signal of the constant envelope is as follows:
wherein beta islFor modulating information, betal＝alT/l, j is an imaginary number symbol, T represents the pulse width, k is the total number of orthogonal bases, l is an orthogonal base variable, l is more than or equal to 1 and less than or equal to k, a0The shared signal realizes multi-bit data modulation in a single pulse for an orthogonal base modulation coefficient, and is a single carrier system, and the radar communication shared signal with constant envelope is input into a matched filter to be used as a reference signal of the matched filter;
(3d) and according to the definition of the self-fuzzy function, obtaining the self-fuzzy function of the radar communication shared signal with the constant envelope, and performing resolution analysis on the radar communication shared signal with the constant envelope later.
3. The method of claim 1, wherein the method comprises: the demodulation of the radar communication shared signal with constant envelope in the step (6) specifically includes the following steps:
(6a) inputting the echo into a radar communication data demodulation processing module, extracting the phase of an echo signal, and performing derivation on the phase to obtain a phase derivative;
(6b) multiplying the phase derivative by the orthogonal basis of each order, and performing integration to obtain demodulated parallel code element data;
(6c) inputting the obtained parallel code element data into a parallel-serial converter to be converted into serial code element data, and outputting the serial code element data to finish the radar communication process;
(6d) and comparing the demodulated serial code element data with the serial communication data to be transmitted to obtain the proportion of the error code element in the total code element, namely the error rate of the radar communication shared signal with constant envelope, and analyzing the demodulation performance of the radar communication shared signal with constant envelope.
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