CN103401661B - A kind of integrated decoding method based on MIMO radar communication - Google Patents

Abstract

The invention provides an integrated coding method based on MIMO radar communication. Orthogonal spread spectrum coding sequence is based on WalsH matrix to ensure the orthogonality of bipolar phase spread spectrum coding sequence. The genetic algorithm is used to meet the radar's requirements for detecting signal autocorrelation peaks and cross-correlation peaks with low sidelobes. Signal coding is based on the idea of soft-spread bi-orthogonal coding. In order to meet the requirements of MIMO radar for detection signals, different spread spectrum coding sequences are used in different coding symbol positions; a dedicated transmission channel is reserved as a time-frequency synchronization reference, and the first coding symbol position of each transmission channel It is also reserved as a phase reference, and special synchronization spreading codes are arranged on these positions. Aiming at the actual needs of radar/radio frequency integration, the present invention makes targeted improvements to the existing carrier frequency offset extraction technology, carrier phase offset extraction technology, and soft-spread dual-orthogonal decoding method, supplemented by α-β as the core frequency Offset tracking technology ensures the accuracy of data frequency offset correction.

Description

An Integrated Encoding and Decoding Method Based on MIMO Radar Communication

technical field

The present invention relates to radar communication technology.

Background technique

Through the organic combination of radar and communication equipment, a comprehensive radio frequency integrated system is formed, which not only helps to coordinate and control the work of electronic equipment on the combat platform in real time, allocate system resources reasonably, but also facilitates the generalization, miniaturization and Versatility. This has very important practical significance and military value for expanding the scope of application of military equipment and improving the overall combat effectiveness, reliability and maintainability of military electronic equipment.

The existing research on radio frequency integration is mainly carried out on the phased array radar system, and the integrated working mode based on waveform sharing is one of the more popular research directions. However, due to the limitation of its own working method, it is difficult for the narrow beam of traditional phased array radar to simultaneously cover long-range communication objects such as detection and tracking targets, missiles, and own aircraft. Communication and detection tasks must be carried out in time, and the integrated system time and energy efficiency is severely limited.

MIMO (Multiple-Input Multiple-Out-put) communication, that is, multiple antennas are placed at the transmitting station and multiple antennas are placed at the receiving station. Combined with space-time coding technology, a MIMO communication link can be formed between the transmitting station and the receiving station. In this way, the channel fading can be suppressed, and the channel capacity of the wireless communication system can be doubled and the bit error rate can be reduced without increasing the bandwidth and antenna transmission power.

Inspired by MIMO communication, Lincoln Laboratory proposed the concept of MIMO radar. The concept of centralized MIMO radar is a further promotion of the concept of phased array and digital array radar. It divides the antenna array into several blocks, each of which sends out orthogonal signal waveforms, and adopts a wide-sending and wide-receiving working mode. Electromagnetic energy cannot be superimposed in phase in space to synthesize a high-gain narrow beam, but forms a lower-gain beam. The wide beam covers a large airspace range, increasing the duty cycle and accumulation time to compensate for the lack of antenna gain.

For a radar system working in MIMO mode, the target to be detected and tracked and the remote communication object can easily be in the detection beam of the MIMO radar at the same time. Therefore, the integrated radio frequency system based on MIMO technology is more feasible and practical. As long as a reasonable encoding method is selected and the communication information is included in the radar detection waveform in a specific format, the information can be transmitted to the communication equipment within the beam irradiation range while completing target tracking or detection, thereby effectively improving the radio frequency integrated system. time and energy efficiency. When using large time-width phase-coded signals, the system parameters of MIMO radar and spread spectrum communication are very close, and the waveform design and codec scheme of spread spectrum communication are also important foundations of the integrated radio frequency system.

Soft spread spectrum is a kind of spread spectrum communication, which adopts (N, k) coding, that is, a spread spectrum code with a length of N is used to represent k-bit information, and k-bit information has 2 ^k states, and different states correspond to Different spread spectrum codes, so as to achieve the purpose of spread spectrum, the spread rate is N/k (see literature: spread spectrum communication and its multiple access technology [M]. Zeng Xingwen, Liu Naian, Sun Xianpu. Xi'an: Xidian University Press ,year 2004). The spreading codes used in soft spreading must be mutually orthogonal and have low autocorrelation peak sidelobes and low cross-correlation values. The genetic algorithm can be used to optimize the low autocorrelation peak sidelobe under the premise of satisfying the orthogonality. encoding of lobes and low cross-correlation values. (Binary orthogonal code design for MIMO radar systems [C]. Sun Ying, Zishu He, Hongming Liu, Li Jun, Shangwei Gao. 2010 International Symposium on Intelligent Signal Processing and Communication system (ISPACS2010), December 6-8, 2010.).

The soft-spread dual-orthogonal coding scheme is to modulate a certain bit of communication information into the phase of the carrier on the basis of soft-spread, and select two phases of 0 or π according to the positive or negative of the bit. It can reduce the demand for the number of spreading codes when the amount of communication information is constant; or increase the amount of information in communication information when the amount of information is given Ding Wei, Tian Hongxin, Yi Kechu. Radio Engineering [J]. 2003.); This coding scheme is also good for improving the confidentiality of the communication system.

The radio frequency integration technology based on MIMO technology must fully consider the difference in requirements between radar and communication systems, and solve the compatibility design and use of radar-communication signals. Among them, the radar requires that the signals of each transmission channel have low autocorrelation peak sidelobe and low cross-correlation value, and when realizing DOD (radio wave departure angle) measurement, it is also required that the transmission signals of each channel meet strict orthogonality; and for To achieve reliable and efficient information transmission, when designing an integrated waveform, it is necessary to take into account issues such as information volume and decoding synchronization requirements. Finding a reasonable codec scheme is the key to the integrated radio frequency technology under the MIMO background.

Contents of the invention

The technical problem to be solved by the present invention is to provide an integrated encoding and decoding method suitable for MIMO radar communication.

The technical solution sampled by the present invention for solving the above-mentioned technical problems is an integrated encoding method based on MIMO radar communication, comprising the following steps:

MIMO radar setting steps: MIMO radar sets M transmission channels, each channel contains L+1 coding symbols; the Mth transmission channel is reserved as the time-frequency synchronization reference; the first coding code of the remaining M-1 channels The element is reserved as a phase offset reference, and the last L coded symbols are information bits, and each information bit has p states;

Spread spectrum code waveform generation steps: optimize the generated (M-1) Lp+M+L sub-code strings by genetic algorithm, and number these sub-code strings as C ₁ , C ₂ , ..., C _{(M-1 )} L _p+M+L , the subcode string is a basic code sequence used as a spreading code;

Source information encoding step: Divide the communication information to be transmitted by the radar detection beam into two parts and encode them separately; the first part of information is encoded according to the unipolar p-ary encoding rule q ₁ ,q ₂ ,…,q _{( M-1)L} , the second part is coded according to the bipolar binary coding rule b ₁ ,b ₂ ,…b _(M-1)L ; the two parts of communication information are evenly distributed to the front In M-1 channels;

Transmit signal sequence generating step: correspondingly multiply the two parts of communication information in each channel, that is, use the first part of communication information to determine the subcode string of each channel information bit, and combine the subcode string of each information bit with the second part of communication information Multiply correspondingly to obtain the coding sequence of the information part in the detection signal; add the respective phase offset reference codes PR _i to the first M-1 channels, where the corresponding relationship between PR _i and subcode strings is: PR _i =C _{(M -1) Lp+i} , i=1,2,...,M-1; fill in the fixed sequence TF formed by L+1 fixed subcode strings in the reserved time-frequency reference channel, Finally, the transmit signal sequence of each transmit channel of the MIMO radar is obtained.

An integrated decoding method based on MIMO radar communication, comprising the following steps:

Data receiving step: the receiver receives the data X(n) obtained by down-conversion and sampling, the system sampling rate is 1/T _C , and T _C is the chip interval of the sub-code string; judge whether there is a priori information of the frequency offset at the current moment , if there is, enter the time synchronization step, otherwise enter the frequency offset search and tracking initial step;

The initial step of frequency offset search and tracking: search for frequency offset between transceiver stations Start the α-β filter by using the searched frequency offset result, and adjust the frequency offset track, remember

Time synchronization step: generate the same baseband signal sequence H ₀ (n), 1≤n≤(L+1 )N; modulate the baseband signal sequence H ₀ (n) in the α-β filter at the m-1th moment to the predicted value of the frequency offset at the mth moment Above, m is the current moment of receiving data, and the modulated signal H(n) is Process the sampling data X(n) and the modulation signal H(n) to obtain the processing result y(n), *Indicates a conjugate complex number; the starting time n ₀ of the received signal is determined by the peak position of the correlation processing, and the effective data X _C (n) is intercepted according to the starting time n ₀ of the received signal: X _C (n)=X(n) ,n ₀ ≤n≤(L+1)N;

Carrier frequency offset correction steps:

Perform frequency offset correction on the valid data X _C (n) to obtain frequency offset corrected effective data y _C (n), ${\mathrm{the\; y}}_C\left(\mathrm{no}\right)=x_C\left(\mathrm{no}\right)e^{-\mathrm{j\Δ}{\widehat{\mathrm{\ω}}}_{m/m-1}\mathrm{no}{T}_C},$ n ₀ ≤n≤(L+1)N;

Carrier phase offset extraction step: intercept the data corresponding to the phase offset reference in the frequency offset correction effective data y _C (n) will data Multiply and sum with the phase offset reference code PR _i respectively to get the sum result i=1,2,...,M-1; calculate the summation result phase of and will As the estimated value of the phase deviation of the i-th channel;

Splitting processing step: segment the effective frequency offset correction data y _C (n) in units of length N, and send the obtained L segments of data to M-1 related receivers corresponding to the decoding branch for decoding Processing, the data sent to the kth decoding branch is expressed as: y _k (n)=y _C (kN+nn ₀ ), k=1,2,...L,1≤n≤N, k=1,2 ,...,M-1; then divide the data sent into each relevant receiver into p branches, and the signal of each branch is multiplied and summed with the subcode string of its corresponding state; k=1,2,...L, i=1,2,...M-1, q=1,2,...p; It is the result of multiplying and summing the kth signal in the i-th correlation receiver with the subcode string C _{(i-1)Lp+(k-1)p+q} ;

Phase offset correction step: the signal of each branch is multiplied by the subcode string of its corresponding state and the summation result is multiplied by the phase offset estimation factor to obtain the phase offset correction result; i=1,2,…M-1;k=1,2,…,L;q=1,2,…,p, among them, Multiply and sum the k-th signal with its corresponding state subcode string in the i-th correlation receiver The phase offset correction result of is the phase bias estimation factor of the i-th channel;

Comparison decision step: the phase offset correction result Take the real part Make a comparison and judgment to obtain the first part of the communication information q _(i-1)L+k transmitted by the radar transmitter: q _(i-1)L+k =q _i,k ,i=1,2,...M-1 ;k=1,2,...,L, q _i,k is the maximum absolute value output branch number of the i-th correlation receiver of the k-th decoding branch; judge the phase offset correction result Take the real part , get the second part of the communication information b _(i-1)L+k transmitted by the radar transmitter: i=1,2,…M-1;k=1,2,…,L; combine the first part of communication information q _(i-1)L+k with the second part of communication information b _{(i-1)L+ k} are combined separately to obtain two parts of communication information transmitted by the MIMO radar transmitter.

Orthogonal spread spectrum coding sequence is based on WalsH matrix to ensure the orthogonality of bipolar phase spread spectrum coding sequence. The genetic algorithm is used to meet the radar's requirements for detecting signal autocorrelation peaks and cross-correlation peaks with low sidelobes. Signal coding is based on the idea of soft-spread bi-orthogonal coding. In order to meet the requirements of MIMO radar for detection signals, different spread spectrum coding sequences are used in different coding symbol positions; a dedicated transmission channel is reserved as a time-frequency synchronization reference, and the first coding symbol position of each transmission channel It is also reserved as a phase reference, and special synchronization spreading codes are arranged on these positions. Aiming at the actual needs of radar/radio frequency integration, the present invention makes targeted improvements to the existing carrier frequency offset extraction technology, carrier phase offset extraction technology, and soft-spread dual-orthogonal decoding method, supplemented by α-β as the core frequency Offset tracking technology ensures the accuracy of data frequency offset correction. While maintaining the performance of MIMO radar detection and tracking, it solves the problem of using radar detection waveforms to transmit communication information.

Further, during the integrated decoding based on MIMO radar communication, an α-β filter state update step is provided, as follows:

The frequency offset prediction value of the m-th time to the m-th time with the α-β filter As the center, select 2G+1 frequency offset points: g∈[-G,G], is the selected g-th frequency offset point; T _C is the chip interval of the subcode string; the baseband signal sequence H ₀ (n) is modulated to these frequency points respectively to obtain the modulated signal H _g (n); $h_g\left(\mathrm{no}\right)=h_0\left(\mathrm{no}\right)e^{-\mathrm{jn\Δ}{\widehat{\mathrm{\ω}}}_g{T}_C},$ n∈[1,(L+1)N];

Use effective data X _C (n) to process the modulated signal H _g (n), and the output peak value U _g after processing is, g=-G,-G+1,...,G; compare the peak output results, find the largest output peak U _j , U _j =max(U _g );

Calculate the measured value of frequency offset estimation at time m according to the frequency point △ω′ _m corresponding to U _j for:

Among them, k _d is the linear fitting slope of the error voltage, U _j+1 is the output peak value corresponding to the j+1th frequency point, and U _j-1 is the output peak value corresponding to the j-1th frequency point;

Calculate the △(△ω _m ) residual of frequency offset estimation at time m as Get the frequency offset estimate at the current moment Calculate the estimated value of the frequency offset change rate at the current moment ΔT is the time interval between two data collections;

Calculate the estimated value of the frequency offset at the next moment and an estimate of the rate of change of the frequency offset

$\begin{array}{c}\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}\\ {\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\end{array}\begin{array}{c}\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; \&Delta;T</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\end{array}\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}\\ {\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}\end{array}\right]<span\; class="notranslate">\; .</span>$

The benefit of the present invention is that it provides a coding and decoding method for the integrated radar/communication radio frequency system under the background of MIMO technology, so that the MIMO radar can maintain the normal detection and tracking of the target, and at the same time use the radar signal to send a signal to the target within the beam coverage. Transfer information to complete tasks such as guidance or monitoring.

Description of drawings

Figure 1 is a schematic diagram of communication reception.

Fig. 2 is a schematic diagram of phase offset extraction.

FIG. 3 is a schematic diagram of correlation reception of the kth information bit of the i-th channel.

Figure 4 is the self-blurring map of the 4th channel when N=128 and L=6.

Figure 5 is the mutual blurring diagram of the 2nd and 3rd channels when N=128 and L=6.

FIG. 6 is a relationship curve between the signal-to-noise ratio of the received signal and the bit error rate.

detailed description

For a better description, the following definitions are made:

Spreading subcode string: the basic coding sequence optimized by the genetic algorithm and prepared to be used as a spreading code is called a spreading subcode string, referred to as a subcode string;

Coding symbol: When encoding a signal, subcode strings need to be combined according to certain rules, and the position used to place the subcode string is called a coding unit.

Information bit: The coding unit that carries communication information is called an information bit.

Phase offset reference: used to realize the phase offset extraction is called a phase offset reference, and the first coding unit of each transmission channel is reserved as a phase offset reference.

Time-frequency reference channel: The reserved transmission channel specially used to provide carrier synchronization and time reference is called time-frequency reference channel.

Unipolar p-ary encoding: each symbol of the signal has 1, 2,..., p total of p states, and the method of encoding the corresponding state value after quantizing the information is called unipolar p-ary coding.

1. Encoding process:

It is assumed that the MIMO radar has M transmission channels, and each channel contains L+1 coded symbols. Reserve the Mth transmission channel as the time-frequency synchronization reference; the first coding symbol of the remaining M-1 channels is reserved as the phase offset reference, and the last L coding symbols are information bits, and each information bit has p states . An integrated spread-spectrum phase-encoded detection signal generation method capable of taking into account the functions of MIMO radar target detection, tracking and information transmission has the following steps:

Step 1 Spread spectrum code waveform design: use genetic algorithm to optimize (M-1) Lp+M+L sub-code strings, and number these sub-code strings in turn as C ₁ , C ₂ ,...,C _{(M-1 ) Lp+M+L} .

Step 2 source information encoding:

Step 2-1 divides the communication information to be transmitted by the radar detection beam into two parts and encodes them respectively. The first part of information is encoded according to the unipolar p-ary encoding rule, and the second part is encoded according to the bipolar binary encoding rule. The two parts of communication information obtained after encoding can be expressed as:

Part 1: q ₁ ,q ₂ ,…,q _(M-1)L ;

Part 2: b ₁ , b ₂ , . . . b _(M-1)L .

Wherein, 1≤q _j ≤p; b _j =1 or -1; j=1,2,...,(M-1)L. The maximum amount of information in a single frame is (M-1)(log ₂ (p ^L )+L) bits.

In step 2-2, the two parts of communication information are evenly distributed to the first M-1 channels in units of L symbols. The allocation results are shown in Table 1:

Table 1. Communication information that needs to be modulated for each channel

Step 3 Generate MIMO radar quadrature two-phase coding transmit signal sequence:

Step 3-1 Use the first part of communication information to determine the subcode strings of the information bits of each channel, and multiply the subcode strings of the information bits with the second part of the communication information to obtain the coded sequence of the information part in the detection signal, where the i The encoded waveform of the kth information bit of a channel can be expressed as:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; LP</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; q</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}}}$

Step 3-2 Add the respective phase offset reference codes PR _i to the first M-1 channels, and the corresponding relationship between PR _i and subcode strings is:

PR _i =C _(M-1)Lp+i ,i=1,2,...,M-1

Fill the reserved time-frequency reference channel with a fixed sequence composed of L+1 fixed subcode strings, including:

TF=[TF ₁ ,...,TF _L+1 ]

Among them, TF _j =C _{(M-1)Lp+M-1+j} ,j=1,2,...L+1.

Finally, the transmit signal sequence of each transmit channel of the MIMO radar is obtained, as shown in Table 2:

Table 2. Signal encoding of each channel

Step 4 Generate transmit signal:

Through the digital signal generating equipment and the up-conversion circuit of each transmission channel, the code sequence of each channel is modulated to the radar operating frequency to form a dedicated detection signal for the MIMO integrated system.

The integrated coding of radar communication under the background of MIMO needs to convert the communication information into Included in each transmit channel of the radar.

The invention uses the idea of soft-spreading dual-orthogonal to code each transmitting channel of the radar, and uses a genetic algorithm to optimize the spread-spectrum code. In order to successfully demodulate the information carried in the soft-spreading biorthogonal encoding phase, the present invention uses the first encoding symbol of each channel as a phase offset reference to realize the phase offset estimation of its own channel; at the same time, in order to realize time synchronization For the tracking of carrier frequency offset, the present invention reserves a special channel as a time-frequency reference channel. This channel does not carry communication information, and always sends a specific coded signal known to both parties.

After the integrated encoding, each transmission channel of the radar still satisfies strict orthogonality; Figure 4 and Figure 5 draw the self- and mutual ambiguity function diagrams between channel signals when the number of transmission channels M=5. From the results of the fuzzy diagram, we can see that In the integrated system, the signals of each transmitting channel of the radar have low autocorrelation peak sidelobe and low cross-correlation value.

2. Decoding process:

Under the background of integration, the decoding process of communication receiving equipment mainly includes the following contents:

(1) Time synchronization

In the integrated working mode, the radar transmits communication information to the communication equipment in the form of pulses. Therefore, the communication equipment first needs to achieve time synchronization in order to intercept effective pulse signals and extract information.

(2) Carrier frequency offset tracking

Radar and communication receiving equipment use different local oscillators. After the received signal is digitally down-converted, the signal will still be modulated by the carrier frequency offset, which will affect the subsequent decoding process. Therefore, the communication receiving equipment needs to adjust the carrier frequency offset. Do track memory. The α-β filter is used to realize the real-time memory of the frequency offset value, which can ensure the accuracy of data frequency offset correction.

(3) Phase deviation extraction

During the transmission process of each channel signal, the initial phase will have a certain deviation, which will affect the accurate demodulation of the initial phase of each channel signal, thereby affecting the extraction of the second part of the communication information carried by the radar detection waveform. Therefore, communication decoding must extract the phase deviation of each channel signal and perform phase compensation on each channel signal.

(4) Communication decoding

As shown in Figure 1, the specific steps of decoding are as follows:

Step 1 Data reception:

Step 1-1 Receive the down-converted and sampled data from the receiver, denoted as X(n), the system sampling rate is 1/T _C , and T _C is the chip interval of the subcode string.

Step 1-2 judges whether the receiving end has the prior information of the frequency offset at the current moment, if yes, directly go to step 3, otherwise go to step 2.

Step 2 frequency offset search and tracking start

Step 2-1 Search for frequency offset between transceiver stations

Step 2-2 utilizes several search results from step 2-1 Start the alpha-beta filter and start to Track and remember.

Step 3 time synchronization

Assuming that the time of receiving data this time is time m, the frequency offset prediction value of the α-β filter at the m-1th time to the m-th time is

Step 3-1 generates the baseband signal sequence H ₀ (n), 1≤n≤(L+1)N, which is the same as the Mth transmission channel of the radar according to the coding rules, expressed in the form of a table:

TF ₁ TF ₂ … TF _L+1

Step 3-2 modulates H ₀ (n) at Above, the modulated signal is denoted as H(n), and H(n) can be expressed as:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Step 3-4 Correlate H(n) and X(n) according to the following formula.

$\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; N</span>}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Step 3-5 Determine the starting time n ₀ of the received signal according to the peak position of the correlation operation, and intercept valid data, which is recorded as X _C (n):

X _C (n)=X(n),n ₀ ≤n≤(L+1)N(3)

Step 4 Carrier frequency offset correction

Use the following formula to correct the frequency offset of X _C (n):

${\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j\&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Step 5 Extract carrier phase offset:

Step 5-1 intercepts the data corresponding to the phase deviation reference in y _C (n), expressed as:

${\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Step 5-2 is shown in Figure 2, the Multiply and sum with PR _i , i=1,2,...,M-1 respectively:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; P</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Step 5-3 Calculate complex numbers The phase of i=1,2,…,M-1 is denoted as i=1,2,…,M-1, and As the estimated value of the phase offset of the i-th channel.

In step 6, the effective data is processed in a branch with the length N as the unit.

Step 6-1: Segment y _C (n) in units of length N, and send the obtained L-segment data to M-1 related receivers corresponding to the decoding branch for decoding processing, and a single decoding branch As shown in Figure 3. Among them, the data sent to the kth decoding branch can be expressed as:

y _k (n)=y _C (kN+nn ₀ ),k=1,2,…L,1≤n≤N(7)

Step 6-2 As shown in Figure 3, the data sent to each relevant receiver is divided into p branches, and the signal of each branch is multiplied and summed with the subcode string of its corresponding state, as shown in formula (8):

$Y_q^{i,k}=\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{the\; y}}_k\left(\mathrm{no}\right)C_{(i-1)\mathrm{LP}+(k-1)p+q}\left(\mathrm{no}\right);$ (8)

k=1,2,...L,i=1,2,...M-1,q=1,2,...p

(8) where is the result of multiplying and summing the k-th channel signal and the subcode string C _{(i-1)Lp+(k-1)p+q} in the i-th correlation receiver.

Step 7 Phase Offset Correction

Will multiplied by the bias estimator The result is as follows:

Step 8 compares the judgment and obtains the communication information transmitted by the radar transmitter

Step 8-1 will Take the real part for comparison and judgment, record the maximum absolute value output branch number of the i-th correlation receiver of the k-th decoding branch as q _i,k , and obtain the first part of the communication information transmitted by the radar transmitter:

q _(i-1)L+k =q _i,k ,i=1,2,…M-1;k=1,2,…,L(10)

Step 8-2 Judgment The symbol of , get the second part of the communication information transmitted by the radar transmitter:

${\mathrm{<span\; class="notranslate">\; b</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Y</span>}}_{{\mathrm{<span\; class="notranslate">\; q</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{{\mathrm{<span\; class="notranslate">\; q</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; |</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

Step 8-3 Combine q _(i-1)L+k , b _(i-1)L+k , i=1,2,...M-1,k=1,2,...,L respectively to get Two parts of communication information transmitted by the MIMO radar transmitter.

Step 9 α-β filter status update

Step 9-1 to As the center, select 2G+1 frequency offset points:

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; g</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; \&Element;</span><span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Step 9-2 modulates H ₀ to these frequency points respectively:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; jn\&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; g</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \&Element;</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

Step 9-3 uses these modulated signal sequences to perform correlation processing on the data obtained in step 4, and record the output peak value as U _g , g=-G, -G+1,...,G.

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; |</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; *</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

Step 9-4 Compare the peak output results, find the largest output peak and record it as U _j =max(U _g ,g=-G+1,…,G-1), and record the frequency point corresponding to U _j as △ω′ _m , the measured value of frequency offset estimation is

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 15</span>}<span\; class="notranslate">\; )</span>$

Among them, k _d is the linear fitting slope of the error voltage.

Step 9-5 calculates the residual error of frequency offset estimation as

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 16</span>}<span\; class="notranslate">\; )</span>$

Steps 9-6 utilize the formula

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 17</span>}<span\; class="notranslate">\; )</span>$

Get the frequency offset estimate at the current moment

Steps 9-7 utilize the formula

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&Delta;T</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 18</span>}<span\; class="notranslate">\; )</span>$

Calculate the estimated value of the frequency offset change rate at the current moment In the formula, ΔT is the time interval between two data collections.

Steps 9-8 utilize the formula

$\begin{array}{c}\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}\\ {\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\end{array}\begin{array}{c}\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; \&Delta;T</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\end{array}\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}\\ {\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; m</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 19</span>}<span\; class="notranslate">\; )</span>$

Calculate the frequency offset prediction value at the next moment and update the state variables.

Example

1. Coding

Set M=5, L=6, p=2, reserve the fifth channel as the time-frequency reference channel; and assume that the chip width of the subcode string is Tc=10 ^-6 s, the length of the subcode string is N=128, and the carrier Frequency ω/2π=10 ⁹ Hz.

In the first step, use the genetic algorithm to obtain 59 subcode strings with a length of 128 and number them.

In the second step, use MATLAB to randomly generate the communication information of the first part and the communication information of the second part respectively:

Part 1: 2, 1, 2, 2, 2, 1, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2.

Part 2: -1, 1, 1, -1, -1, 1, 1, 1, 1, -1, -1, -1, 1, -1, -1, 1, 1, -1, - 1, 1, -1, -1, -1, -1.

In the third step, the two parts of communication information are allocated to the information bits of the four transmission channels, and the allocation results are shown in Table 3:

Table 3. Communication information that needs to be modulated for each channel

Step 4: From the first part of the information in Table 3, select the corresponding subcode strings for the information bits of each transmission channel, and the second part of the information modulates the initial phase for the selected subcode strings, so as to obtain the information of the first four transmission channels of the radar The bits are encoded as follows:

First channel: -C ₂ , C ₃ , C ₆ , -C ₈ , -C ₁₀ , C ₁₁ ;

Second channel: C ₁₃ , C ₁₆ , C ₁₈ , -C ₁₉ , -C ₂₁ , -C ₂₄ ;

The third channel: C ₂₅ , -C ₂₈ , -C ₃₀ , C ₃₁ , C ₃₄ , -C ₃₅ ;

Fourth channel: -C ₃₈ , C ₄₀ , -C ₄₂ , -C ₄₄ , -C ₄₆ , -C ₄₈ .

The fifth step is to encode the phase offset reference bits of the first 4 channels and the fifth channel (time-frequency synchronization channel), and obtain the final encoding results of each transmission channel of the radar as shown in Table 4:

Table 4. Coding of each transmission channel of the radar

Figure 4 and Figure 5 show the self-blurring diagram of the 4th emission channel and the mutual blurring diagram of the 2nd and 3rd channels. From the results in Fig. 4 and Fig. 5, it can be seen that the transmitted signal has very low autocorrelation peak sidelobe and small cross-correlation value; moreover, it can be seen from the signal self-fuzzy map that it is in the shape of a thumbtack, and the radar detection waveform has a significant effect on the Doppler The information is more sensitive, the ability to detect low-speed targets is strong, and it has better range resolution. In addition, because MIMO radar uses low-gain wide-beam irradiation, it has better anti-intercept performance than traditional phased array radar.

Two, decoding

Suppose the distance between the communication equipment and the radar is 5000m, the carrier frequency offset △ω/2π=500Hz, the signal-to-noise ratio of the received signal is 12dB, and the sampling rate of the receiving equipment is 1/T _C .

The first step is to capture the carrier frequency offset.

In the second step, use the results of the first step to perform time synchronization and carrier frequency offset correction on the next set of data.

Step 3, estimate the phase offset of the corrected signal.

The fourth step is to decode the communication, and the decoding result is as follows:

The first part of information after decoding

The second part of information after decoding

Step 5, calculate the frequency offset prediction value from the current moment to the next moment.

It can be seen from the decoding result that when the signal-to-noise ratio is 12dB, the despreading decoding method of the present invention can accurately obtain the original coded information.

Get the signal-to-noise ratio-30～30dB, draw the relationship curve of the signal-to-noise ratio and the bit error rate as shown in Figure 6, as can be seen from the curve, when the signal-to-noise ratio is greater than 10dB, the despreading decoding method of the present invention can accurately solve the radar emission The communication information contained in the signal.

Claims (3)

1. an integrated coding method based on MIMO radar communication, is characterized in that, comprises the following steps: MIMO radar setting steps: MIMO radar sets M transmission channels, each channel contains L+1 coding symbols and reserves the Mth transmission channel as the time-frequency synchronization reference; the first coding symbols of the remaining M-1 channels Reserved as a phase offset reference, the last L coded symbols are information bits, and each information bit has p states; Spreading code waveform generation steps: use the genetic algorithm to optimize the generated (M-1)Lp+M+L sub-code strings, and number these sub-code strings in turn as C ₁ , C ₂ , ..., C _{(M-1 )Lp+M+L} , the subcode string is a basic code sequence used as a spreading code; Source information encoding step: Divide the communication information to be transmitted by the radar detection beam into two parts and encode them separately; the first part of information is encoded according to the unipolar p-ary encoding rule q ₁ ,q ₂ ,…,q _{( M-1)L,} the second part is coded according to the bipolar binary coding rules b ₁ ,b ₂ ,…b _(M-1)L ; the two parts of communication information are evenly distributed to the front In M-1 channels; Transmit signal sequence generation step: use the first part of communication information to determine the subcode string of each channel information bit, and multiply the subcode string of information bit by the second part of communication information to obtain the code sequence of the information part in the detection signal; Add their respective phase offset reference codes PR _i to the first M-1 channels, where the corresponding relationship between PR _i and subcode strings is: PR _i =C _(M-1)Lp+i , i=1,2,... ., M-1; fill in a fixed sequence TF composed of L+1 fixed subcode strings in the reserved time-frequency reference channel, and finally obtain the transmit signal sequence of each transmit channel of the MIMO radar. 2. an integrated decoding method based on MIMO radar communication, is characterized in that, comprises the following steps: Data receiving step: the receiver receives the data X(n) obtained by down-conversion and sampling, the system sampling rate is 1/T _C , and T _C is the chip interval of the sub-code string; judge whether there is a priori information of the frequency offset at the current moment , if there is, enter the time synchronization step, otherwise enter the frequency offset search and tracking initial step; The initial step of frequency offset search and tracking: search for frequency offset between transceiver stations Start the α-β filter by using the searched frequency offset result, and adjust the frequency offset track, remember Time synchronization step: generate the same baseband signal sequence H ₀ (n), 1≤n≤(L+1 )N; modulate the baseband signal sequence H ₀ (n) in the α-β filter at the m-1th moment to the frequency offset prediction value at the mth moment Above, m is the current moment of receiving data, and the modulated signal H(n) is Process the sampling data X(n) and the modulation signal H(n) to obtain the processing result y(n), *Indicates a conjugate complex number; the starting time n ₀ of the received signal is determined by the peak position of the correlation processing, and the effective data X _C (n) is intercepted according to the starting time n ₀ of the received signal: X _C (n)=X(n) ,n ₀ ≤n≤(L+1)N; Carrier frequency offset correction steps: Perform frequency offset correction on the valid data X _C (n) to obtain frequency offset corrected effective data y _C (n), Carrier phase offset extraction step: intercept the data corresponding to the phase offset reference in the frequency offset correction effective data y _C (n) will data Multiply and sum with the phase offset reference code PR _i respectively to get the sum result Compute the sum result phase of and will As the estimated value of the phase deviation of the i-th channel; Splitting processing step: segment the effective frequency offset correction data y _C (n) in units of length N, and send the obtained L segments of data to M-1 related receivers corresponding to the decoding branch for decoding Processing, the data sent to the kth decoding branch is expressed as: y _k (n)=y _C (kN+nn ₀ ), k=1,2,...L,1≤n≤N, k=1,2 ,...,M-1; then divide the data sent into each relevant receiver into p branches, and the signal of each branch is multiplied and summed with the subcode string of its corresponding state; k=1,2,...L, i=1,2,...M-1, q=1,2,...p; It is the result of multiplying and summing the kth signal with the subcode string C _{(i-1)Lp+(k-1)p+q} in the i-th correlation receiver; Phase offset correction step: the signal of each branch is multiplied by the subcode string of its corresponding state and the summation result is multiplied by the phase offset estimation factor to obtain the phase offset correction result; i=1,2,...M-1; k=1,2,...,L; q=1,2,...,p, where, Multiply and sum the k-th signal with its corresponding state subcode string in the i-th correlation receiver The phase offset correction result of is the phase bias estimation factor of the i-th channel; Comparison decision step: the phase offset correction result Take the real part Make a comparison and judge to obtain the first part of the communication information q _(i-1)L+k transmitted by the radar transmitter: q _(i-1)L+k =q _i,k ,i=1,2,...M-1 ;k=1,2,...,L, q _i,k is the maximum absolute value output branch number of the i-th correlation receiver of the k-th decoding branch; judge the phase offset correction result Take the real part , get the second part of the communication information b _(i-1)L+k transmitted by the radar transmitter: i=1,2,...M-1; k=1,2,...,L; combine the first part of the communication information q _(i-1)L+k with the second part of the communication information b _{(i-1)L+ k} are combined separately to obtain two parts of communication information transmitted by the MIMO radar transmitter. 3. a kind of integrated decoding method based on MIMO radar communication as claimed in claim 2, is characterized in that, also comprises α-β filter status update step: The frequency offset prediction value of the m-th time to the m-th time with the α-β filter As the center, select 2G+1 frequency offset points: g∈[-G,G], is the selected g-th frequency offset point; T _C is the chip interval of the subcode string; the baseband signal sequence H ₀ (n) is modulated to these frequency points respectively to obtain the modulated signal H _g (n); n∈[1,(L+1)N]; Use effective data X _C (n) to process the modulated signal H _g (n), and the output peak value U _g after processing is, g=-G,-G+1,...,G; compare the peak output results, find the largest output peak value U _j , U _j =max(U _g ); Calculate the measured value of frequency offset estimation at time m according to the frequency point Δω′ _m corresponding to U _j for: Among them, k _d is the linear fitting slope of the error voltage, U _j+1 is the output peak value corresponding to the j+1th frequency point, and U _j-1 is the output peak value corresponding to the j-1th frequency point; Calculate the Δ(Δω _m ) residual of the frequency offset estimate at time m as Get the frequency offset estimate at the current moment Calculate the estimated value of the frequency offset change rate at the current moment ΔT is the time interval between two data collections; Calculate the estimated value of the frequency offset at the next moment and an estimate of the rate of change of the frequency offset