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CN108983226B - MIMO radar communication integration method based on antenna array modulation - Google Patents

MIMO radar communication integration method based on antenna array modulation Download PDF

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CN108983226B
CN108983226B CN201810805263.8A CN201810805263A CN108983226B CN 108983226 B CN108983226 B CN 108983226B CN 201810805263 A CN201810805263 A CN 201810805263A CN 108983226 B CN108983226 B CN 108983226B
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waveform
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CN108983226A (en
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王向荣
龙倩
曹先彬
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Beihang University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0891—Space-time diversity
    • H04B7/0897—Space-time diversity using beamforming per multi-path, e.g. to cope with different directions of arrival [DOA] at different multi-paths

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Abstract

The invention discloses an MIMO radar communication integration method based on antenna array modulation, and belongs to the technical field of radar and communication. The method comprises the steps of firstly, constructing a reference dictionary and designing a constellation diagram according to an MIMO radar system; carrying out phase rotation on the transmitted waveform at the transmitting end, and updating a constellation diagram; then dividing a binary communication data stream to be sent into a plurality of code elements, and finding out an array element-waveform pairing mode corresponding to each code element; and finally, the radar transmitting end adjusts the transmitting array structure by changing the state of the radio frequency switch to transmit the corresponding radar pulse waveform. And the radar receiving end processes the radar echo to realize target detection. A communication receiving end processes radar pulse signals to obtain an ordered guide vector estimation value of a radar transmitting array; and traversing the constellation points in the constellation diagram, finding out the constellation point with the minimum distance with the ordered guide vector estimation value, and demodulating the binary information. The invention realizes the downlink transmission of communication, obviously improves the data transmission rate, reduces the communication error rate and enhances the system reliability.

Description

MIMO radar communication integration method based on antenna array modulation
Technical Field
The invention belongs to the technical field of radar and communication, and particularly relates to an MIMO radar communication integration method based on antenna array modulation.
Background
For a long time, the difference of processing mechanisms between radar and communication is studied as two independent systems, and the two systems have a large overlap in frequency spectrum, so that the two systems can be mutually inhibited as interference.
The demand for radio frequency spectrum resources from a wide variety of commercial communication devices has multiplied exponentially, and radar continues to lose spectrum to civilian areas while maintaining proper functionality. For example, existing radar systems, depending on their type and use, can be deployed in the radio frequency spectrum of 0.3 to 100GHz, where many bands are well suited for international mobile communications, e.g., the 700 to 3600MHz band is widely used in 2G, 3G, and 4G cellular mobile communications standards. It is expected that as more and more wireless communication devices access the wireless network, mobile traffic will continue to increase, spectrum resource competition will become more intense, and interference between radar and communication devices will be more severe.
In fact, radar is a communication system that performs a specific task by analyzing and processing radio echoes, and the two have a certain technical compatibility. The radar is used for realizing the communication function, so that coexistence of the radar and the radar is realized, and an effective solution is provided for relieving frequency band congestion and improving spectrum efficiency.
The concept of integration of radar communication has emerged in the 60 s of the 20 th century, and the research thereafter can be roughly divided into three types of mechanisms: the first is a split beam mechanism, i.e. multiple beams are used, with different wave velocities performing different functions, such as detection and communication; the second is a time-sharing mechanism, the radar and communication functions multiplex the aperture and other software and hardware resources in a time-sharing manner, detection cannot be carried out at the same time during communication, and a detection blind area exists. The third is a simultaneous mechanism, namely an integrated mechanism, and the radar detection waveform and the communication modulation waveform are fused together; the waveform carries communication data, and the communication receiver demodulates the waveform signal and extracts communication information; and processing the reflected echo at a radar receiver to extract target information. Meanwhile, communication and radar detection are considered, and a detection blind area does not exist.
The radar communication integration is to realize the communication function by utilizing the radar and modulate communication data on a radar signal, and is the most natural idea of a simultaneous mechanism. However, the biggest problems of the integrated design of radar communication are: how to eliminate mutual interference while sharing spectrum and resources.
To address this problem, prior art document 1: dual-function radar communication: information modulation using sidelobe control and waveform diversity. Moeness g.amin; yimin d.zhang, IEEE signal processing journal, volume 64,8(2015), 2168-; a method based on Amplitude Modulation (AM) is provided, the idea is that communication symbols are represented by controlling Side Lobe Levels (SLL) of radar beams in a communication direction, and a communication receiver demodulates different communication symbols by setting a plurality of threshold detection side lobe Levels. However, such systems can only communicate when the communication receiver is located in the side lobe region of the radar beam, and cannot communicate when the communication receiver is located within the main lobe region of the radar.
Document 2: dual function radar communication based on phase rotation invariance Aboulnasr Hassanien; moeness g.amin; yimin d.zhang; fauzia Ahmad, 23 rd European conference on Signal processing, 2015, 1346-1350; a difunctional radar communication integration mechanism based on phase rotation invariance is provided, the idea is that communication symbols are mapped to phase rotation amount of waveforms, phase rotation is carried out on the transmitted orthogonal waveforms by changing transmitted beam forming weight vectors, the communication symbols are modulated, and a receiving end demodulates and obtains binary information by detecting the phase rotation amount.
The two integrated mechanisms are based on a single-input multi-output phased array radar, and are not suitable for a multi-input multi-output (MIMO) radar.
As a new radar system, the MIMO radar has the advantages of good waveform diversity and space diversity and can obviously improve the performance of the system. Aboulnasr Hassanien et al propose a method for realizing MIMO radar communication integration by using Frequency Hopping (FH) waveform: as in document 3: a dual-function MIMO radar communication system based on frequency hopping waveforms Aboulnasr Hassanien; braham Himed; rising, IEEE radar conference in 2017, 1721-; the method includes the steps of sending orthogonal waveforms generated by frequency hopping codes to achieve radar target detection, modulating a Phase Shift Keying (PSK) communication symbol in each frequency hopping to achieve a communication function, enabling the number of the communication symbols which can be modulated by each radar pulse to be equal to the number of transmitting array elements multiplied by the length of the frequency hopping codes, and detecting the PSK symbols through a Phase discriminator at a receiving end to demodulate. The coexistence of MIMO radar and communication can be achieved not only by the above waveform diversity, but also by making full use of the spatial degree of freedom given by the antenna array structure, which has not been found in the literature at present.
Disclosure of Invention
Aiming at the problems, the invention aims to develop an MIMO radar communication integrated mechanism which does not affect the normal detection function of a radar and simultaneously realizes communication downlink transmission; an MIMO radar communication integration method based on antenna array modulation is provided.
The method comprises the following specific steps:
initializing an MIMO radar system, and constructing a reference dictionary and a design constellation diagram;
the initialization specifically comprises the following steps:
the method comprises the following steps that the number of array elements of a uniform linear transmitting array of the MIMO radar is given to be M, the number of array elements of a receiving array is given to be N, all the array elements are omnidirectional antennas, and the transmitting array is in equal-interval linear distribution;
the number of the radio frequency front ends is K, and the transmitting orthogonal waveform set psi (t) consists of K waveforms psik(t), K ═ 1,. i ',. j',. K; the signals are orthogonal to each other, i.e.:
Figure BDA0001738023970000021
constructing a reference dictionary specifically comprises:
at the radar transmitting end, each radar pulse carries a symbol conveying communication data, each symbol representing NbBit information; each of NbThe bit information combination respectively corresponds to an array element-waveform pairing mode; when the composition mode of the transmitting array and the orthogonal waveform correspondingly transmitted by the array elements are changed, different array element-waveform pairing modes are adopted, and different ordered guide vectors are generated, namely the elements in the guide vectors of the transmitting array are ordered. Selecting the optimal one from all pairing modes to meet the radar performance or communication performance requirements due to different radar performance or communication performance requirements of the system
Figure BDA00017380239700000310
Array element-waveform pairing method, from
Figure BDA0001738023970000031
And sorting to form a reference dictionary.
Transmitting ordered guide vectors of array after array element-waveform pairing
Figure BDA0001738023970000032
The calculation is as follows:
Figure BDA0001738023970000033
where M (τ) ═ Q (τ) P (τ), τ denotes the number of radar pulses; q (tau) is a K multiplied by K dimensional waveform array matrix of the uniform linear emission array; p (tau) is a K multiplied by M dimensional array element selection matrix of a uniform linear emission array; a (θ) is an M × 1 dimensional steering vector of the uniform linear transmit array, e represents an exponential function exp (·); j represents an imaginary number; k0 is 2 pi/lambda to represent wave number, and lambda is the wavelength of radar emission waveform; p is a radical ofkE { 0.. and M-1} represents the array element position in the connected state, and K orthogonal transmission waveforms psik(t) by being located at pkThe array elements are simultaneously transmitted out; d is the array element spacing of the transmitting array distributed in linear equal spacing,
Figure BDA0001738023970000034
θ represents an angle.
When radar performance or communication performance is considered, the specific requirements are as follows:
(a) when the system requires good radar performance, the pairing mode is to enable the beam pattern formed by the transmitting array to be fitted to the expected pattern to the maximum extent;
(b) when the system requires good communication performance, the pairing should be such that the distance between the ordered steering vectors generated by the different transmit arrays is maximized.
The specific design process of the constellation diagram is as follows:
theta when the communication receiver is located at the radar transmitting arraycWhen in azimuth, the dictionary will be referred to
Figure BDA0001738023970000035
Ordered guide vector corresponding to array element-waveform pairing mode
Figure BDA0001738023970000036
Determining constellation points and N as constellation pointsbAnd the mapping relation between the bit information forms a constellation diagram.
Step two, aiming at the azimuth angle of the known communication receiver of the radar, phase rotation is carried out on the transmitted waveform at the transmitting end, and a constellation diagram is updated;
azimuth angle theta of known communication receiver for radarcIntroducing a phase rotation vector at a transmitting array element to carry out phase rotation on a transmitting waveform; the phases generated by the M antennas are uniformly distributed on the circumference, so that the phase ambiguity existing in the transmitting array steering vector is eliminated, and the distance between the ordered steering vectors is increased;
rotation vector of setting phase
Figure BDA0001738023970000037
Wherein the phase rotation factor is:
Figure BDA0001738023970000038
where M denotes the mth array element of the uniform linear transmit array, and M is 1.
After the phase rotation is introduced, the updated steering vector of the transmitting array is equivalent to:
Figure BDA0001738023970000039
after the phase rotation is introduced, the steering vector of the transmitting array is independent of the communication direction, thereby eliminating the phase ambiguity and ensuring the maximum distance between the code elements.
Step three, at the radar transmitting end, the binary communication data stream to be transmitted is carried out according to NbAnd dividing the bits/code elements into a plurality of code elements, wherein each radar pulse carries one code element, and finding out an array element-waveform pairing mode corresponding to each code element according to the reference dictionary index.
And fourthly, aiming at a certain divided code element A, the radar transmitting end changes the state of the radio frequency switch, readjusts the transmitting array structure according to the array element-waveform pairing mode corresponding to the code element A, and transmits the corresponding radar pulse waveform.
The specific process is as follows: and converting the divided code element A into a decimal number B, selecting an array element-waveform pairing mode with the sequence number B from a reference dictionary, reconstructing array element-waveform pairing arrangement by a radar transmitting end, and transmitting radar pulse waveforms to generate corresponding B-number ordered guide vectors.
Processing radar echoes by a radar receiving end to normally realize target detection; meanwhile, the communication receiving end processes radar pulse signals, extracts information of transmitted waveforms through a matched filter bank, removes channel influence and obtains an ordered guide vector estimation value of a radar transmitting array:
at the radar transmitting end, each radar pulse carries a symbol conveying communication information, each symbol representing NbBit information; each of NbThe bit information combination respectively corresponds to an array element-waveform pairing mode; when the composition of the transmitting array and the orthogonal waveforms transmitted by the corresponding array elements (i.e. different array element-waveform pairing modes) are changed, different ordered steering vectors (defined herein as ordered steering vectors, i.e. the elements in the steering vectors of the transmitting array are ordered) are generated. For the τ -th radar pulse, the received signal x (t; τ) of the radar receiving array is expressed as:
Figure BDA0001738023970000041
wherein Q represents the number of far-field targets located within the radar detection area; beta is aq(τ) is the reflection coefficient of the qth target; thetaqAzimuth angle of the qth target relative to the radar transmit array and the receive array; a (theta)q) For a M x 1 dimensional steering vector of a uniform linear transmit array to the qth target, Ψ (t; τ) is the vector of the transmitted signal, b (θ)q) For an Nx 1-dimensional steering vector for the qth target radar receive array: n (t; tau) is an additive noise plus interference term;
theta at radar transmit array for communication receivercReceived signal x of communication receiver in azimuthc(t; τ) is expressed as:
Figure BDA0001738023970000042
wherein alpha ischIs a channel coefficient, nc(t) is the channel noise plus interference term.
The specific process of processing the radar pulse signal by the communication receiving end is as follows:
first, a received signal x to a communication receiverc(t; τ) performing matched filtering to obtain:
Figure BDA0001738023970000051
wherein n isc(τ)＝vec{∫Tnc(t；τ)ΨH(t) dt } and vec {. cndot } represent the pulling of the matrix into a column vector.
Then, the matched filtered output signal y is processedc(τ) removing the influence of the channel parameters to obtain an estimated value of the ordered steering vector of the transmit array;
expressed as:
Figure BDA0001738023970000052
and step six, traversing all constellation points in the constellation map, finding out the constellation point with the minimum distance with the ordered guide vector estimation value, and demodulating the binary information.
Firstly, traversing the constellation points, and finding out the constellation point with the minimum distance to the ordered steering vector estimation value determined in the step five, wherein the formula is as follows:
Figure BDA0001738023970000053
then, the binary information is demodulated according to the mapping relation between the constellation points and the binary bits.
The invention has the following advantages:
1) the MIMO radar communication integration method based on antenna array modulation provides a feasible design scheme for a dual-function MIMO radar communication integration system.
2) The MIMO radar communication integration method based on antenna array modulation can realize downlink transmission of communication under the condition of not influencing normal detection of the radar, and can remarkably improve data transmission rate, reduce communication error rate and enhance system reliability.
3) Compared with the existing integrated system design method, the MIMO radar communication integrated method based on antenna array modulation gives full play to the space diversity advantage of the MIMO radar, and has higher data transmission rate and waveform design freedom.
4) The MIMO radar communication integration method based on antenna array modulation can realize communication downlink transmission, save resources and reduce cost while not influencing normal detection targets of the radar.
Drawings
Fig. 1 is a flowchart of an MIMO radar communication integration method based on antenna array modulation according to the present invention;
FIG. 2 is a schematic diagram of a MIMO radar transmit-receive array structure according to the present invention;
FIG. 3 is a schematic diagram of sparse antenna arrangement of the MIMO radar of the present invention;
FIG. 4 shows the present invention NbUnder the condition of 8, the working principle of the MIMO radar transmitting end is shown schematically;
FIG. 5 shows the present invention NbUnder the condition of 8, the working principle of the communication receiving end is shown in a schematic diagram;
FIG. 6 shows a diagram of N in an embodiment of the present inventionbUnder the condition of 1,2,4 and 8, the signal-to-noise ratio-bit error rate diagram of the dual-function MIMO radar communication integrated system is shown.
Detailed Description
The present invention will be described in further detail below with reference to the accompanying drawings.
The invention relates to an MIMO radar communication integrated method based on antenna array modulation, which is used for sparsely arranging an emission array of an MIMO radar, generating a plurality of ordered steering vectors by an array element-waveform pairing arrangement method, modulating communication information and constructing a radar communication integrated signal; the system complexity can be reduced while the radar spatial resolution is ensured, and high-speed effective downlink communication transmission is realized.
As shown in fig. 1, the specific steps are as follows:
initializing an MIMO radar system, and constructing a reference dictionary and a design constellation diagram;
the initialization specifically comprises the following steps:
the structure of the MIMO radar transmit-receive array is shown in FIG. 2, the number of array elements of a given MIMO radar uniform linear transmit array is M, the number of array elements of a receive array is N, all the array elements are omnidirectional antennas, and the transmit arrays are in equidistant linear distribution;
the number of the radio frequency front ends is K, and the transmitting orthogonal waveform set psi (t) consists of K waveforms psik(t), K ═ 1,. i ',. j',. K; the signals are orthogonal to each other, i.e.:
Figure BDA0001738023970000061
and during a single radar pulse, selecting K array elements to be respectively connected with the radio frequency front end to form a K-antenna sparse transmitting array. Each array element selects a waveform Ψ (t) from a set Ψ (t) of transmit orthogonal waveformsk(t), K1, K emits as shown in fig. 3. For array element-waveform pairing, it is common
Figure BDA0001738023970000062
And (4) selecting.
Let P denote a K × M-dimensional array element selection matrix, Q denote a K × K-dimensional waveform array matrix, and M ═ QP denotes a K × M-dimensional array element-waveform pairing matrix.
Constructing a reference dictionary specifically comprises:
at the radar transmitting end, each radar pulse carries a symbol conveying communication data, each symbol representing NbBit information; each of NbThe bit information combination respectively corresponds to an array element-waveform pairing mode; when the composition of the transmitting array and the orthogonal wave form correspondingly transmitted by the array element are changed, different wave forms are adoptedThe array element-waveform pairing mode generates different ordered guide vectors, namely the elements in the guide vectors of the transmitting array are ordered. Selecting the optimal one from all pairing modes to meet the radar performance or communication performance requirements due to different radar performance or communication performance requirements of the system
Figure BDA0001738023970000063
Array element-waveform pairing method, from
Figure BDA0001738023970000064
And sorting to form a reference dictionary.
K x 1 dimension ordered guide vector of transmitting array after array element-waveform pairing
Figure BDA0001738023970000065
The calculation is as follows:
Figure BDA0001738023970000066
where M (τ) ═ Q (τ) P (τ), τ denotes the number of radar pulses; q (tau) is a K multiplied by K dimensional waveform array matrix of the uniform linear emission array; p (tau) is a K multiplied by M dimensional array element selection matrix of a uniform linear emission array; a (theta) is the M x 1 dimensional steering vector of the uniform linear transmit array,
Figure BDA0001738023970000071
represents an exponential function exp (·); j represents an imaginary number; k is a radical of02 pi/lambda represents wave number, and lambda is the wavelength of radar emission waveform; p is a radical ofkE { 0., M-1}, K ═ 1., K denotes the array element position in the connected state, K orthogonal transmit waveforms Ψk(t), K1, K by being located at pkThe array elements are simultaneously transmitted out; d is the array element spacing of the transmitting array distributed in linear equal spacing,
Figure BDA0001738023970000072
θ represents an angle.
When radar performance or communication performance is considered, the specific requirements are as follows:
(a) when the system requires good radar performance, the pairing mode is to enable the beam pattern formed by the transmitting array to be fitted to the expected pattern to the maximum extent;
(b) when the system requires good communication performance, the pairing should be such that the distance between the ordered steering vectors generated by the different transmit arrays is maximized.
The specific design process of the constellation diagram is as follows:
theta when the communication receiver is located at the radar transmitting arraycWhen in azimuth, the dictionary will be referred to
Figure BDA0001738023970000073
Ordered guide vector corresponding to array element-waveform pairing mode
Figure BDA0001738023970000074
Determining constellation points and N as constellation pointsbAnd the mapping relation between the bit information forms a constellation diagram.
Step two, aiming at the azimuth angle of the known communication receiver of the radar, phase rotation is carried out on the transmitted waveform at the transmitting end, and a constellation diagram is updated, so that the phases generated by the M antennas are uniformly distributed on the circumference, thereby eliminating phase ambiguity possibly existing in the transmitting array steering vector and increasing the distance between the ordered steering vectors;
first, when the azimuth angle theta of the communication receivercGreater than a critical value
Figure BDA0001738023970000075
Obtained in the first step
Figure BDA0001738023970000076
During demodulation, due to the 2 pi periodicity of the phase, phase ambiguity occurs, estimation is inaccurate (for example, the ordered steering vector which should be a is estimated at the receiving end as the ordered steering vector B), and correct transmission of communication data is affected. When theta iscEven more, the communication cannot be performed by using the ordered steering vector. So that the phase rotation is performed to ensure the final demodulation accuracyAnd (8) determining.
Moreover, the phases in the transmitting array steering vectors after phase rotation are uniformly distributed on the circumference, which is beneficial to increasing the distance between the ordered steering vectors and improving the performance of the communication system.
Azimuth angle theta of known communication receiver for radarcIntroducing a phase rotation vector at a transmitting array element to carry out phase rotation on a transmitting waveform; rotation vector of setting phase
Figure BDA0001738023970000077
Wherein the phase rotation factor is:
Figure BDA0001738023970000078
where M denotes the mth array element of the uniform linear transmit array, and M is 1.
After the phase rotation is introduced, the updated steering vector of the transmitting array is equivalent to:
Figure BDA0001738023970000079
(3) the equation shows that after the phase rotation is introduced, the steering vector of the transmitting array is independent of the communication direction, thus eliminating the phase ambiguity.
Step three, at the radar transmitting end, the real binary communication data stream to be transmitted is transmitted according to NbDividing bits/code elements into a plurality of code elements, wherein each code element corresponds to an array element-waveform pairing mode; each radar pulse carries a code element, and the array element-waveform matching mode corresponding to each code element is found out according to the index of the reference dictionary.
And fourthly, aiming at a certain divided code element A, the radar transmitting end changes the state of the radio frequency switch, readjusts the transmitting array structure according to the array element-waveform pairing mode corresponding to the code element A, and transmits the corresponding radar pulse waveform.
The specific process is as follows: and converting the divided code element A into a decimal number B, selecting an array element-waveform pairing mode with the sequence number B from a reference dictionary, reconstructing array element-waveform pairing arrangement by a radar transmitting end, and transmitting radar pulse waveforms to generate corresponding B-number ordered guide vectors.
As shown in FIG. 4, when N isbWhen the number of the array elements is 8, the MIMO radar transmitting end divides a binary sequence '01100100.... 10100100' to be transmitted into 8 bits/code element, converts the code element '01100100' into a decimal number equal to 100, selects an array element-waveform pairing mode with the sequence number of 100 from a reference dictionary, reconstructs array element-waveform pairing arrangement, and transmits radar pulse waveforms, so that corresponding No. 100 ordered guide vectors are generated.
Processing radar echoes by a radar receiving end to normally realize target detection; meanwhile, the communication receiving end processes radar pulse signals, extracts information of transmitted waveforms through a matched filter bank, removes channel influence and obtains an ordered guide vector estimation value of a radar transmitting array:
for the radar receiving end, when the operation of the radar receiving end on the transmitting end is known, the MIMO radar can normally realize the target detection function.
For the τ -th radar pulse, the received signal x (t; τ) of the radar receiving array is expressed as:
Figure BDA0001738023970000081
wherein Q represents the number of far-field targets located within the radar detection area; beta is aq(τ) is the reflection coefficient of the qth target, which is generally considered to follow the Swerling-II target model; thetaqFor a q-th target, the azimuth angle of the target relative to the radar antenna array is defined, for a far-field target, the distance between the transmitting array and the receiving array relative to the far-field detection target is extremely small, and the transmitting array and the receiving array can be considered to have the same azimuth angle; a (theta)q) For a M x 1 dimensional steering vector of a uniform linear transmit array to the qth target, Ψ (t; τ) is the vector of the transmitted signal, b (θ)q) Is an Nx 1-dimensional steering vector for the qth target radar receiving array;
Figure BDA0001738023970000082
n (t; tau) is an additive noise plus interference term;
for a communication receiving end, after a receiver receives a radar pulse signal, information of a transmitting waveform is extracted through a matched filter bank, channel influence is removed, and an ordered guide vector of a radar transmitting array is obtained.
Theta at radar transmit array for communication receivercReceived signal x of communication receiver in azimuthc(t; τ) is expressed as:
Figure BDA0001738023970000091
wherein alpha ischIs a channel coefficient, nc(t) is the channel noise plus interference term.
The specific process of processing the radar pulse signal by the communication receiving end is as follows:
first, a received signal x to a communication receiverc(t; τ) performing matched filtering to obtain:
Figure BDA0001738023970000092
wherein n isc(τ)＝vec{∫Tnc(t；τ)ΨH(t) dt }; vec {. denotes operators that pull the matrix into a column vector.
As can be seen from the equation (6), the output signal after matched filtering contains complete information of the ordered steering vector of the radar transmitting array. When the radar transmits signals, different ordered guide vectors can be generated due to different structures of the radar, and the received signals contain complete ordered guide vector information, so that the invention provides the method for modulating communication information by changing antenna arrangement and utilizing the ordered guide vectors of the radar transmitting array to realize the integration of MIMO radar communication.
Then, the matched filtered output signal y is processedc(tau) removing the influence of the channel parameters to obtain an estimate of the ordered steering vector of the transmit array；
Expressed as:
Figure BDA0001738023970000093
step six, traversing the constellation diagram
Figure BDA0001738023970000094
And (4) finding out the constellation point with the minimum distance from the ordered guide vector estimation value, and demodulating the binary information.
Firstly, traversing the constellation points, and finding out the constellation point with the minimum distance to the ordered steering vector estimation value determined in the step five, wherein the formula is as follows:
Figure BDA0001738023970000095
then, the binary information is demodulated according to the mapping relation between the constellation points and the binary bits specified by the constellation diagram.
As shown in FIG. 5, when N isbAnd when the radar pulse signal is received by the communication receiving end, the radar pulse signal is sent to the matched filter bank to extract the information of the transmitted waveform, the channel influence is removed, and the ordered guide vector estimation value of the radar transmitting array is obtained. Comparing the distances of the steering vectors with all constellation points, the distance between the steering vectors and the No. 100 ordered steering vector is the minimum. According to the mapping relation of the constellation diagram, the binary information obtained by demodulation is '01100100'.
In order to verify the correctness of the invention, relevant simulation experiments are carried out. The simulation parameters are shown in table 1:
TABLE 1
Figure BDA0001738023970000096
Figure BDA0001738023970000101
As shown in FIG. 6, at NbUnder the conditions of 1,2,4 and 8, the signal-to-noise ratio-bit error rate curve of the MIMO radar communication integrated system is drawn. Simulation shows that under the mechanism, when the signal-to-noise ratio is increased, the system bit error rate can reach 10-5The order of magnitude is less.
In summary, the simulation example is only for explaining the idea of the radar communication integration method, and does not limit the protection scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (5)

1. An MIMO radar communication integration method based on antenna array modulation is characterized by comprising the following specific steps:
initializing an MIMO radar system, and constructing a reference dictionary and a design constellation diagram;
constructing a reference dictionary specifically comprises:
at the radar transmitting end, each radar pulse carries a symbol conveying communication data, each symbol representing NbBit information; each of NbThe bit information combination respectively corresponds to an array element-waveform pairing mode; different ordered guide vectors are generated by adopting different array element-waveform pairing modes; selecting the optimal one from all pairing modes to meet the radar performance or communication performance requirements due to different radar performance or communication performance requirements of the system
Figure FDA0002799176490000011
Array element-waveform pairing method, from
Figure FDA0002799176490000012
Sorting to form a reference dictionary;
transmitting ordered guide vectors of array after array element-waveform pairing
Figure FDA0002799176490000013
The calculation is as follows:
Figure FDA0002799176490000014
where M (τ) ═ Q (τ) P (τ), τ denotes the number of radar pulses; q (tau) is a K multiplied by K dimensional waveform array matrix of the uniform linear emission array; p (tau) is a K multiplied by M dimensional array element selection matrix of a uniform linear emission array; a (θ) is an M × 1 dimensional steering vector of the uniform linear transmit array, e represents an exponential function exp (·); j represents an imaginary number; k is a radical of02 pi/lambda represents wave number, and lambda is the wavelength of radar emission waveform; p is a radical ofkE { 0.. and M-1} represents the array element position in the connected state, and K orthogonal transmission waveforms psik(t) by being located at pkThe array elements are simultaneously transmitted out; d is the array element spacing of the transmitting array distributed in linear equal spacing,
Figure FDA0002799176490000015
θ represents an angle;
the specific design process of the constellation diagram is as follows:
when the communication receiver is positioned at the azimuth angle theta of the radar transmitting arraycWhen above, reference will be made to the dictionary
Figure FDA0002799176490000016
Ordered guide vector corresponding to array element-waveform pairing mode
Figure FDA0002799176490000017
Determining constellation points and N as constellation pointsbMapping relation between bit information to form a constellation diagram;
step two, aiming at the azimuth angle of the known communication receiver of the radar, phase rotation is carried out on the transmitted waveform at the transmitting end, and a constellation diagram is updated;
azimuth angle theta of known communication receiver for radarcIntroducing a phase rotation vector at a transmitting array element to carry out phase rotation on a transmitting waveform; the phases generated by the M antennas are uniformly distributed on the circumference, thereby eliminating the existence of the transmitting array steering vectorsThe phase is fuzzy, and the distance between the ordered guide vectors is increased;
rotation vector of setting phase
Figure FDA0002799176490000018
Wherein the phase rotation factor is:
Figure FDA0002799176490000019
wherein M represents the mth array element of the uniform linear transmit array, and M is 1.
After the phase rotation is introduced, the updated steering vector of the transmitting array is equivalent to:
Figure FDA00027991764900000110
after phase rotation is introduced, the guide vector of the transmitting array is irrelevant to the communication direction, so that phase ambiguity is eliminated, and the maximum distance between code elements is ensured;
step three, at the radar transmitting end, the binary communication data stream to be transmitted is carried out according to NbDividing each code element of bits into a plurality of code elements, wherein each radar pulse carries one code element, and finding out an array element-waveform pairing mode corresponding to each code element according to a reference dictionary index;
fourthly, aiming at a certain divided code element A, the radar transmitting end changes the state of a radio frequency switch, readjusts the transmitting array structure according to the array element-waveform pairing mode corresponding to the code element A, and transmits a corresponding radar pulse waveform;
processing radar echoes by a radar receiving end to realize target detection; meanwhile, the communication receiving end processes radar pulse signals, extracts information of transmitted waveforms through a matched filter bank, removes channel influence and obtains an ordered guide vector estimation value of a radar transmitting array:
for the τ -th radar pulse, the received signal x (t; τ) of the radar receiving array is expressed as:
Figure FDA0002799176490000021
wherein Q represents the number of far-field targets located within the radar detection area; q (tau) is a K multiplied by K dimensional waveform array matrix of the uniform linear emission array; p (tau) is a K multiplied by M dimensional array element selection matrix of a uniform linear emission array; beta is aq(τ) is the reflection coefficient of the qth target; thetaqAzimuth angle of the qth target relative to the radar transmit array and the receive array; a (theta)q) For a M x 1 dimensional steering vector of a uniform linear transmit array to the qth target, Ψ (t; τ) is the vector of the transmitted signal, b (θ)q) For an Nx 1-dimensional steering vector for the qth target radar receive array: n (t; tau) is an additive noise interference term;
azimuth angle theta of radar transmission array for communication receivercReceived signal x of communication receiverc(t; τ) is expressed as:
Figure FDA0002799176490000022
wherein alpha ischIs a channel coefficient, nc(t) is a channel noise interference term; m (τ) ═ Q (τ) P (τ), τ denotes the number of radar pulses;
the specific process of processing the radar pulse signal by the communication receiving end is as follows:
first, a received signal x to a communication receiverc(t; τ) performing matched filtering to obtain:
Figure FDA0002799176490000023
wherein n isc(τ)＝vec{∫Tnc(t；τ)ΨH(t) dt }, vec {. cndot } represents the pulling of the matrix into a column vector;
Figure FDA0002799176490000024
indicating the azimuth angle theta when the communication receiver is positioned in the radar transmitting arraycOrdered steering vectors of the upper time; ΨH(t) represents a conjugate transpose of the set of transmit orthogonal waveforms Ψ (t);
then, the matched filtered output signal y is processedc(τ) removing the influence of the channel parameters to obtain an estimated value of the ordered steering vector of the transmit array;
expressed as:
Figure FDA0002799176490000031
and step six, traversing all constellation points in the constellation map, finding out the constellation point with the minimum distance with the ordered guide vector estimation value, and demodulating the binary information.
2. The MIMO radar communication integration method based on antenna array modulation according to claim 1, wherein the initialization in the step one specifically includes:
the method comprises the following steps that the number of array elements of a uniform linear transmitting array of the MIMO radar is given to be M, the number of array elements of a receiving array is given to be N, all the array elements are omnidirectional antennas, and the transmitting array is in equal-interval linear distribution; the number of the radio frequency front ends is K, and the transmitting orthogonal waveform set psi (t) consists of K waveforms psik(t), K ═ 1,. i ',. j',. K; the signals are orthogonal to each other, i.e.:
Figure FDA0002799176490000032
3. the MIMO radar communication integration method based on antenna array modulation according to claim 1, wherein the specific requirements of radar performance or communication performance in the step one are:
(a) when the system requires good radar performance, the pairing mode enables a beam pattern formed by the transmitting array to be fitted to a desired pattern to the maximum extent;
(b) when the system requires good communication performance, the pairing mode maximizes the distance between the ordered steering vectors generated by different transmitting arrays.
4. The MIMO radar communication integration method based on antenna array modulation according to claim 1, wherein the specific process of the step four is as follows: and converting the divided code element A into a decimal number B, selecting an array element-waveform pairing mode with the sequence number B from a reference dictionary, reconstructing array element-waveform pairing arrangement by a radar transmitting end, and transmitting radar pulse waveforms to generate corresponding B-number ordered guide vectors.
5. The MIMO radar communication integration method based on antenna array modulation according to claim 1, wherein the sixth step specifically comprises:
firstly, traversing the constellation points, and finding out the constellation point with the minimum distance to the ordered steering vector estimation value determined in the step five, wherein the formula is as follows:
Figure FDA0002799176490000033
then, the binary information is demodulated according to the mapping relation between the constellation points and the binary bits.
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