A communication-aware integrated waveform optimization method for interference mitigation

Abstract

The application relates to a communication and sensing integrated waveform optimization method for anti-interference, and belongs to the wireless communication field.The application is characterized in that: a transmitter generates a basic pseudo-random noise (PRN) code, and generates a plurality of CSK symbols through cyclic shift; a CSK modulated signal uses a multi-ary coding mode, so that data bits can correspond to a plurality of different code sequences, thereby realizing signal modulation and obtaining modulated communication information data; a communication and sensing integrated waveform is designed based on a code shift keying (CSK) signal and a radar linear frequency modulation signal, the distance resolution and the detection distance of the radar can be improved without increasing the peak power, the CSK high-order modulation has higher frequency band utilization, higher reliability and stronger anti-interference capability; in addition, the sidelobe level of the fuzzy function of the optimized anti-interference communication and sensing integrated waveform is lower, so that the dual targets of efficient communication and accurate sensing can be realized in the integrated system, and the communication and radar performance is excellent.

Description

TECHNICAL FIELD

[0001] The application relates to an anti-interference communication and sensing integrated waveform optimization method, and belongs to the wireless communication field. BACKGROUND

[0002] As the basis of wireless communication and sensing, spectrum resources are limited and scarce. With the development of wireless communication technology and wireless detection technology, radar and communication gradually have more similarities in hardware structure and spectrum resources. The working frequency bands of wireless communication and radar sensing systems largely overlap. In order to explore more available spectrum resources, communication and sensing integration design has become an inevitable trend and has rapidly become one of the core research directions of 6G communication technology. In the six application scenarios defined by the International Telecommunication Union (IMT-2030) for 6G, an integrated sensing and communication (ISAC) system can sense the spatial information, motion state and surrounding environment of a target, thereby providing support for intelligent transportation, smart agriculture, low-altitude economy and many other emerging applications. Integrated waveform design, as one of the key technologies of integrated sensing and communication, has become a hot issue of common concern in the academic and industrial circles.

[0003] Currently, the integrated waveform mainly falls into two categories. Among them, the multiplexed waveform is to use radar and communication waveforms in different time, frequency, space, and other dimensions respectively. However, this approach results in low resource utilization and insufficient integration level. In contrast, the shared waveform integrates radar and communication into one waveform and shares the transmitting end, while the receiving end processes the signals separately. This design not only improves the utilization of spectral resources and hardware and software devices, reduces the use cost, and has a higher integration level. The integrated waveform design is the cornerstone of the integrated sensing. The literature "L. Jiang, S. Yan, Y. Wu, X. Ma et al. Sonar detection performance with LFM-BPSK combined waveforms[C]. OCEANS 2016 - Shanghai, Shanghai China, 2016: 1-4, doi: 10.1109 / OCEANSAP.2016.7485501." studies the binary phase shift keying-linear frequency modulation (BPSK-LFM) integrated signal, which has attracted widespread attention due to its simple structure and wide applicability. However, this type of signal has the problem that the radar ambiguity function is easily disturbed by communication data. Specifically, random communication signals can cause the sidelobe amplitude of the ambiguity function to exceed the threshold, causing the receiver to misjudge false signals and affect the detection performance of the radar. To further improve the anti-interference ability of the integrated signal, the literature "Ren Zhimin, Tang Gaoming, Liu Yuhong, et al. Chirp-DS-BPSK radar communication integrated waveform design[J]. Communications Technology, 2024, 57(8): 783-792. doi: 10.3969 / j.issn.1002-0802.2024.08.004." uses a chaotic sequence to non-periodically spread the BPSK based on the BPSK-LFM integrated signal, thereby forming a direct sequence spread spectrum BPSK-LFM (Direct Sequence Spread Spectrum-BPSK-LFM, DSSS-BPSK-LFM) integrated signal waveform. Compared with BPSK-LFM, this design exhibits superior ambiguity function characteristics. During pulse compression, the peak-to-sidelobe ratio is significantly reduced, and the communication bit error rate is also effectively improved. However, its frequency band utilization is low, greatly limiting the communication information rate, making it difficult to meet the high-speed transmission requirements of the integrated system. SUMMARY

[0004] In view of the problem that the radar signal ambiguity function is seriously affected by communication data, the purpose of the present application is to provide an anti-interference communication and perception integrated waveform optimization method, which designs a communication and perception integrated waveform based on a code shift keying (CSK) signal and a radar linear frequency modulation (LFM) signal, can improve the range resolution and detection distance of the radar without increasing the peak power, and the CSK high-order modulation has higher frequency band utilization, high reliability and strong anti-interference ability; in addition, the sidelobe level of the anti-interference communication and perception integrated waveform optimized by the present application is lower, so that the dual goals of efficient communication and accurate perception can be realized in the integrated system, and the communication and radar performance is excellent.

[0005] The purpose of the present application is realized by the following technical solutions:

[0006] The anti-interference communication and perception integrated waveform optimization method disclosed by the present application comprises the following steps:

[0007] Step one: a transmitter generates a basic pseudo-random noise (PRN) code, and generates a plurality of CSK symbols through cyclic shift, the CSK modulated signal uses a multi-ary encoding mode, so that the data bits can correspond to a plurality of different code sequences, thereby realizing modulation of the signal, and obtaining modulated communication information data.

[0008] CSK (U, N) represents that each CSK symbol represents U bits of information, and lasts for N CSK code periods. The modulation principle of CSK is that the U bits of information originally transmitted in series are mapped to different basic code sequences through cyclic shift of the basic code sequence, and each cyclic shift processed CSK symbol can carry U bits of information. The total number of independent waveforms generated after each round of basic code cyclic shift is , the basic code of CSK is denoted as , and the i-th symbol of CSK is denoted as , wherein i=0, 1, 2, …, M-1, when the code period is equal to T, there are L chips, and L is greater than or equal to M. The i-th cyclic shift version is denoted as:

[0009] (1)

[0010] Wherein: represents an integer of the cyclic shift of the i-th waveform, is the duration interval of the chip, is the code length of the basic code (not necessarily M), and the LFM signal is a common waveform in a pulse radar system, which improves the range resolution and detection distance of the radar without increasing the peak power. The LFM signal is represented as:

[0011] (2)

[0012] (3)

[0013] wherein, is the amplitude; is the frequency modulation slope, which is determined by the radar pulse duration T and the bandwidth B, i.e.

[0014] (4)

[0015] Step two: In order to achieve high-precision radar perception and high communication rate transmission, the transmitter uses CSK-LFM integrated signal for waveform design. LFM signal is used as the waveform in the pulse radar system, and through pulse compression, the distance resolution and detection distance of the radar are improved without increasing the peak power. The new integrated waveform formed by the combination of CSK signal and LFM signal comprehensively displays the advantages of CSK signal and LFM signal, and the waveform is still a pulse waveform, each pulse duration carries a CSK signal, and the LFM signal is the carrier of the CSK signal. The communication information data and PRN code generated in step one are mapped to obtain the CSK signal, and then the LFM signal is used as the carrier to generate the CSK-LFM modulated signal into the channel; during demodulation, the intermediate frequency signal is subjected to digital down conversion, matched filtering and decision of the best sampling point to obtain the baseband signal, and the demodulated baseband signal is subjected to CSK demapping to output the communication data information.

[0016] The expression of the CSK-LFM communication and perception integrated signal is

[0017] (5)

[0018] wherein: the CSK basic code is denoted as , the i-th symbol of the CSK is denoted as , and the linear frequency modulation signal is denoted as , represents the integer of the cyclic shift of the i-th waveform, the duration interval of the chip, the code length of the basic code, the carrier frequency.

[0019] Step 3: To achieve high reliability and strong anti-interference capability, the receiver receives the CSK-LFM integrated signal, performs digital signal processing on it, calculates the communication bit error rate and bandwidth utilization, and analyzes the bit error rate of the CSK-LFM integrated signal. The random communication data generated by the transmitter is converted from digital to analog, and an analog signal is transmitted through the antenna. After passing through an additive white Gaussian noise channel, the receiver receives the analog signal, performs analog-to-digital conversion, makes a decision on the digital signal, and calculates and compares the bit error rate with the CSK-LFM signal. Compared with low-order modulated integrated inductive signals, the bandwidth utilization of the CSK-LFM integrated inductive signal is significantly improved.

[0020] CSK stands for M-ary orthogonal signaling (MOS), and its vector representation is as follows:

[0021] (6)

[0022] The distance between any two signals is Send signal The received signal is obtained through the channel.

[0023] (7)

[0024] in: Indicates the signal amplitude. The mean is 0 and the variance is 0. Independent Gaussian random variables

[0025] (8)

[0026] send ,when When the receiver makes a correct decision, the probability of a correct decision is:

[0027] (9)

[0028] (10)

[0029] According to equations (9) and (10), the probability of making an incorrect judgment is:

[0030] (11)

[0031] (12)

[0032] in: Number in base 1 For spreading ratio, The amplitude attenuation coefficient caused by the Doppler frequency shift. This refers to the number of bits per symbol. The bandwidth utilization of CSK-LFM is... Where: N is the length of the code sequence, and each symbol can transmit Bit information, M is the number of available code patterns. Where B is the symbol rate and B is the bandwidth. The CSK-LFM signal is characterized by improved anti-interference capability through spread spectrum, making it suitable for high-robust scenarios. However, the bandwidth utilization of CSK-LFM is significantly higher than that of DSSS-BPSK-LFM. .in: Where B is the symbol rate, B is the bandwidth, and N is the length of the code sequence.

[0033] Step 4: Characterize the radar's resolution capability in both range and Doppler frequency shift dimensions using a radar ambiguity function. (This involves the ambiguity function and communication code metadata of the CSK-LFM integrated signal.) and LFM carrier The first part is the autocorrelation function of the communication symbol, which is shaped like a thumbtack; the second part is equal to the ambiguity function of the classic LFM, which is shaped like a knife edge. Therefore, the ambiguity function of the integrated waveform is the superposition of the two shapes, which can realize the dual functions of sensing and communication. Moreover, the ambiguity function based on the CSK-LFM integrated signal exhibits a thumbtack-like feature with low sidelobes and high main lobes, which improves the range and velocity resolution of the radar system and is beneficial for low-altitude multi-target detection and tracking.

[0034] Ambiguity function and communication code metadata of CSK-LFM integrated signal and LFM carrier Regarding, Part 1 The first part is the autocorrelation function of the communication symbols, shaped like a thumbtack; the second part is equal to the ambiguity function of the classic LFM, shaped like a knife edge. Therefore, the ambiguity function of the integrated waveform is the superposition of the two shapes, enabling the dual functions of sensing and communication.

[0035] The radar ambiguity function characterizes the radar's resolution capability in two dimensions: range and Doppler frequency shift. The radar ambiguity function is represented by the transmitted signal. The modulus of the two-dimensional cross-correlation function .

[0036] (13)

[0037] in For time delay, For Doppler frequency shift, For signal The conjugate of the signal. Divided into communication code metadata With LFM carrier The normalized complex envelope CSK-LFM signal is

[0038] (14)

[0039] Substituting equation (15) into equation (14), the CSK-LFM signal ambiguity function is:

[0040] (15)

[0041] In the formula: For communication code metadata conjugate, linear frequency modulated carrier The conjugate of . Equation (15) is the product of two parts, the first part being The autocorrelation function is used, while the second part is the same as the traditional LFM fuzzy function. The second part is...

[0042] (16)

[0043] Ambiguity function and communication code metadata of CSK-LFM integrated signal and LFM carrier Regarding, Part 1 The first part is the autocorrelation function of the communication symbol, which has a thumbtack-like shape; the second part is equal to the ambiguity function of the classic LFM, which has a blade-like shape. Therefore, the ambiguity function of the integrated waveform is the superposition of the two shapes, which can realize the dual functions of sensing and communication. The ambiguity function based on the CSK-LFM integrated signal exhibits a thumbtack-like feature with low sidelobes and high main lobes, which improves the range and velocity resolution of the radar system and is beneficial for low-altitude multi-target detection and tracking.

[0044] Step 5: The receiver receives the backscattered integrated signal and processes it through the system function. After the matched filter, envelope detection is performed. The envelope detection output signal... The maximum value is sampled and used for decision-making. The system function of the matched filter is derived from the integrated CSK-LFM waveform. The radar detects target echoes in two states: with or without a target echo. A target echo is detected when the echo voltage exceeds a threshold voltage; otherwise, no target echo is detected. A false alarm occurs when no target echo enters the radar receiver, but the radar mistakes a noise signal for a target echo. A correct detection occurs when a target echo enters the radar receiver and is detected by the radar receiver. False alarm probability. Receive signal in the presence of only noise The detected value exceeds the threshold voltage. The probability of a false alarm is calculated. The detection probability expression for CSK-LFM signals is the same as that for LFM signals because the output of the matched filter depends only on the signal energy and is independent of the specific form of the signal. Analysis of the detection probability shows that, with the false alarm probability remaining constant, the detection probability increases accordingly due to the increase in the signal-to-noise ratio.

[0045] The receiver receives the backscattered integrated signal and passes it through the system function. After the matched filter, envelope detection is performed. The envelope detection output signal... The maximum value is sampled and used for decision-making. The system function of the matched filter is derived from the integrated CSK-LFM waveform. Decision. False alarm probability. Receive signal in the presence of only noise The detected value exceeds the threshold voltage. The probability of.

[0046] (17)

[0047] (18)

[0048] Detection probability It is receiving signals The detected value exceeds the threshold voltage under conditions of added noise. The probability of.

[0049] (19)

[0050] In the formula For signal amplitude, Let V be the variance of the noise signal. It is a zero-order Bessel function. The power is Therefore, the output signal-to-noise ratio of the envelope detector is

[0051] (20)

[0052] The Marcum Q function is defined as

[0053] (twenty one)

[0054] Combining equations (18), (19), (20), and (21), the detection probability is rewritten as follows:

[0055] (twenty two)

[0056] The detection probability expressions for CSK-LFM and LFM signals are the same because the output of the matched filter depends only on the signal energy and is independent of the specific form of the signal. Analysis of the detection probability expressions (19) and (22) shows that, with the false alarm probability remaining constant, the detection probability increases accordingly due to the increase in the signal-to-noise ratio.

[0057] Beneficial effects:

[0058] 1. This invention discloses an integrated communication sensing waveform optimization method for anti-interference. Based on Code Shift Keying (CSK) signals and radar linear frequency modulation (LFM) signals, it designs an integrated sensing waveform. This method can improve the radar's range resolution and detection range without increasing peak power. Furthermore, high-order CSK modulation offers higher bandwidth utilization, higher reliability, and stronger anti-interference capabilities. Employing multi-level CSK modulation, the bandwidth utilization is higher than traditional DSSS-BPSK-LFM waveforms, and the bit error rate is lower under the same signal-to-noise ratio (SNR). The performance advantage is particularly significant when the SNR is higher than -14 dB. In AWGN channels, the proposed CSK-LFM signal has a lower bit error rate than the DSSS-BPSK-LFM signal. Optimized to Bit error rate 10 -6 Under these conditions, the CSK-LFM signal has a 1.3dB signal-to-noise ratio gain advantage over the DSSS-BPSK-LFM signal.

[0059] 2. This invention discloses a waveform optimization method for integrated communication and sensing for anti-interference purposes, using a radar ambiguity function to characterize the radar's resolution capability in two dimensions: range and Doppler frequency shift. The ambiguity function of the CSK-LFM integrated signal and the communication code data are also discussed. and LFM carrier The first part is the autocorrelation function of the communication symbol, which is shaped like a thumbtack; the second part is equal to the ambiguity function of the classic LFM, which is shaped like a knife edge. Therefore, the ambiguity function of the integrated waveform is the superposition of the two shapes, which can realize the dual functions of sensing and communication. Moreover, the ambiguity function of the CSK-LFM integrated signal presents a thumbtack-like feature with low sidelobes and high main lobes. Furthermore, the sidelobes of the CSK-LFM signal are reduced by 3dB compared to the DSSS-BPSK-LFM signal, which improves the range and velocity resolution of the radar system and is beneficial for low-altitude multi-target detection and tracking.

[0060] 3. The present invention discloses a waveform optimization method for communication and sensing integration for anti-interference. The optimized CSK-LFM communication and sensing integrated waveform has lower ambiguity function sidelobe level and bit error rate and higher bandwidth utilization, enabling it to achieve the dual goals of efficient communication and accurate sensing in the integrated system, and has excellent communication and radar performance.

[0061] 4. The present invention discloses a waveform optimization method for communication and sensing integration for anti-interference. The waveform structure is compatible with existing radar and communication systems, requires no additional hardware, and is easy to implement in software radio platforms or dedicated integrated systems. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of chip cyclic shifting in CSK modulation;

[0063] Figure 2 This is a schematic diagram of the structure implemented by CSK modulation;

[0064] Figure 3 This is a block diagram of the CSK-LFM integrated signal generation and demodulation system;

[0065] Figure 4 This is a schematic diagram of the composition of the simulation system of the present invention;

[0066] Figure 5 This is a comparison curve of the bit error rate performance of CSK-LFM and DSSS-BPSK-LFM;

[0067] Figure 6 The figures are three-dimensional plots of the ambiguity functions for LFM, DSSS-BPSK-LFM, and CSK-LFM signals, respectively. Figure 6 (a) is the ambiguity function of the LFM signal. Figure 6 (b) is the ambiguity function of the DSSS-BPSK-LFM signal. Figure 6 (c) is the ambiguity function of the CSK-LFM signal;

[0068] Figure 7 Contour plots of the ambiguity function for LFM, DSSS-BPSK-LFM, and CSK-LFM signals, respectively. Figure 7 (a) is a contour plot of the ambiguity function of the LFM signal. Figure 7 (b) is a contour plot of the ambiguity function of the DSSS-BPSK-LFM signal. Figure 7 (c) is a contour plot of the ambiguity function of the CSK-LFM signal;

[0069] Figure 8 This displays the relationship between the false alarm probability and the detection threshold.

[0070] Figure 9 Showing the relationship between detection probability and signal-to-noise ratio under different false alarm probabilities;

[0071] Figure 10 This shows the impact of different target velocities on the detection probability;

[0072] Figure 11The results are from the simulation of joint range-velocity detection in a multi-target environment. Detailed Implementation

[0073] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0074] Example 1:

[0075] like Figure 3 As shown in the figure, the communication sensing integrated waveform optimization method for anti-interference disclosed in this embodiment has the following specific implementation steps:

[0076] Step 1: As Figure 2 As shown, the transmitter generates a basic pseudo-random noise (PRN) code and generates multiple CSK symbols through cyclic shifting. The CSK modulated signal uses a multi-level encoding method, which enables data bits to correspond to various different code sequences, thereby achieving signal modulation and obtaining modulated communication information data.

[0077] like Figure 1 As shown, CSK(4,1) represents that each CSK symbol represents 4 bits of information, lasting for one CSK code cycle. The modulation principle of CSK is to map the 4 bits of message information that originally needed to be transmitted serially into different basic code sequences through cyclically shifted basic code sequences. Each cyclically shifted CSK symbol can carry 4 bits of information. The total number of independent waveforms generated after each round of basic code cyclic shift is... The CSK basic code is denoted as The i-th symbol of CSK is denoted as Where i = 0, 1, 2, ..., 15, and when the symbol period is equal to T, and there are L chips, L is greater than or equal to M. The i-th cyclic shift version is represented as:

[0078] (twenty three)

[0079] in: The integer representing the cyclic displacement of the i-th waveform. The duration of the chip interval, The LFM signal, a commonly used waveform in pulse radar systems, is the code length of the basic code (not necessarily M). Through pulse compression, it improves the radar's range resolution and detection range without increasing peak power. The LFM signal is represented as:

[0080] (twenty four)

[0081] (25)

[0082] in, Amplitude; frequency modulation slope It is determined by the radar pulse duration T = 100 μs and the bandwidth B = 10 MHz, that is...

[0083] (26)

[0084] Step Two: To achieve high-precision radar sensing and high-speed communication transmission, the transmitter uses an integrated CSK-LFM signal for waveform design. The LFM signal, as a waveform in a pulse radar system, improves the radar's range resolution and detection range without increasing peak power through pulse compression. The new integrated sensing waveform, combining the CSK and LFM signals, leverages the advantages of both signals. The waveform remains a pulse waveform, with one CSK signal carried within each pulse duration, and the LFM signal serving as the carrier of the CSK signal. The communication information data and PRN code generated in Step One are mapped to hexadecimal to obtain the CSK signal. Then, the LFM signal is used as the carrier to generate a CSK-LFM modulated signal that enters the channel. During demodulation, the intermediate frequency signal undergoes digital down-conversion, matched filtering, and selection of the optimal sampling point to obtain the baseband signal. The demodulated baseband signal is then demapped using CSK to output the communication data information.

[0085] The CSK-LFM integrated communication and sensing signal is represented as follows:

[0086] (27)

[0087] Where: the CSK basic code is denoted as The i-th symbol of CSK is denoted as The linear frequency modulated signal is denoted as , The integer representing the cyclic displacement of the i-th waveform. The duration of the chip interval, The code length of the base code, For carrier frequency.

[0088] Step 3: As Figure 5 As shown, to achieve high reliability and strong anti-interference capability, the receiver receives the CSK-LFM integrated signal, performs digital signal processing on the integrated signal, calculates the communication bit error rate and bandwidth utilization, and analyzes the bit error rate of the CSK-LFM integrated signal. The random communication data generated by the transmitter is converted from digital to analog, and an analog signal is transmitted through the antenna. After passing through an additive white Gaussian noise channel, the receiver receives the analog signal, performs analog-to-digital conversion, makes a decision on the digital signal, and calculates and compares the bit error rate with the CSK-LFM signal. Compared with low-order modulated integrated inductive signals, the bandwidth utilization of the CSK-LFM integrated inductive signal is significantly improved.

[0089] CSK stands for M-ary orthogonal signaling (MOS), and its vector representation is as follows:

[0090] (28)

[0091] The distance between any two signals is Send signal The received signal is obtained through the channel.

[0092] (29)

[0093] in: Indicates the signal amplitude. The mean is 0 and the variance is 0. Independent Gaussian random variables

[0094] (30)

[0095] send ,when When the receiver makes a correct decision, the probability of a correct decision is:

[0096] (31)

[0097] (32)

[0098] According to equations (9) and (10), the probability of making an incorrect judgment is:

[0099] (33)

[0100] (34)

[0101] Where: number base The spreading ratio is 16. The amplitude attenuation coefficient due to the Doppler frequency shift is 256. The number of bits per symbol is 0.85. The bandwidth utilization rate is 4. Where: the length N of the code sequence is 256, and each symbol can transmit Bit information, the number of available code patterns M is 16, symbol rate The bandwidth (B) is 10 MHz, with a value of 10 Msps. The CSK-LFM signal is characterized by improved anti-interference capability through spread spectrum, making it suitable for high-robust scenarios. However, the bandwidth utilization of CSK-LFM is significantly higher than that of DSSS-BPSK-LFM. Among them: symbol rate The bandwidth B is 10Msps, the length N of the code sequence is 256.

[0102] Step 4: Characterize the radar's resolution capability in both range and Doppler frequency shift dimensions using a radar ambiguity function. (This involves the ambiguity function and communication code metadata of the CSK-LFM integrated signal.) and LFM carrier The first part is the autocorrelation function of the communication symbols, which is pin-shaped; the second part is equal to the ambiguity function of the classic LFM, which is blade-shaped, such as... Figure 6 As shown in (a), the ambiguity function of the integrated waveform is the superposition of two shapes, which can realize the dual functions of sensing and communication. Furthermore, the ambiguity function based on the CSK-LFM integrated signal exhibits a pinhead-like feature with low sidelobes and high main lobes, which improves the range and velocity resolution of the radar system and is beneficial for low-altitude multi-target detection and tracking.

[0103] Ambiguity function and communication code metadata of CSK-LFM integrated signal and LFM carrier Regarding, Part 1 The first part is the autocorrelation function of the communication symbols, shaped like a thumbtack; the second part is equal to the ambiguity function of the classic LFM, shaped like a knife edge. Therefore, the ambiguity function of the integrated waveform is the superposition of the two shapes, enabling the dual functions of sensing and communication.

[0104] The radar ambiguity function characterizes the radar's resolution capability in two dimensions: range and Doppler frequency shift. The radar ambiguity function is represented by the transmitted signal. The modulus of the two-dimensional cross-correlation function .

[0105] (35)

[0106] in For time delay, For Doppler frequency shift, For signal The conjugate of the signal. Divided into communication code metadata With LFM carrier The normalized complex envelope CSK-LFM signal is

[0107] (36)

[0108] Substituting equation (15) into equation (14), the CSK-LFM signal ambiguity function is:

[0109] (37)

[0110] In the formula: For communication code metadata conjugate, linear frequency modulated carrier The conjugate of . Equation (15) is the product of two parts, the first part being The autocorrelation function is used, while the second part is the same as the traditional LFM fuzzy function. The second part is...

[0111] (38)

[0112] Ambiguity function and communication code metadata of CSK-LFM integrated signal and LFM carrier Regarding, Part 1 The first part is the autocorrelation function of the communication symbols, shaped like a thumbtack; the second part is equal to the ambiguity function of the classic LFM, shaped like a knife edge. Therefore, the ambiguity function of the integrated waveform is the superposition of the two shapes, enabling the dual functions of sensing and communication. For example... Figure 6 (c) shows that the ambiguity function based on the CSK-LFM integrated signal exhibits a pinhead-like feature with low sidelobes and high main lobes, which improves the range and velocity resolution of the radar system and is beneficial for low-altitude multi-target detection and tracking.

[0113] Step 5: The receiver receives the backscattered integrated signal and processes it through the system function. After the matched filter, envelope detection is performed. The envelope detection output signal... The maximum value is sampled and used for decision-making. The system function of the matched filter is derived from the integrated CSK-LFM waveform. The radar detects target echoes in two states: with or without a target echo. A target echo is detected when the echo voltage exceeds a threshold voltage; otherwise, no target echo is detected. A false alarm occurs when no target echo enters the radar receiver, but the radar mistakes a noise signal for a target echo; a correct detection occurs when a target echo enters the radar receiver and is detected by the radar receiver. For example... Figure 8 As shown, the false alarm probability Receive signal in the presence of only noise The detected value exceeds the threshold voltage. The probability of detection. The detection probability expression for CSK-LFM signals is the same as that for LFM signals because the output of the matched filter depends only on the signal energy and is independent of the specific form of the signal. For example... Figure 9 As shown, the detection probability analysis shows that, with the false alarm probability remaining constant, the detection probability increases accordingly due to the increase in the signal-to-noise ratio.

[0114] The receiver receives the backscattered integrated signal and passes it through the system function. After the matched filter, envelope detection is performed. The envelope detection output signal... The maximum value is sampled and used for decision-making. The system function of the matched filter is derived from the integrated CSK-LFM waveform. Decision. False alarm probability. Receive signal in the presence of only noise The detected value exceeds the threshold voltage. The probability of.

[0115] (39)

[0116] (40)

[0117] Detection probability It is receiving signals The detected value exceeds the threshold voltage under conditions of added noise. The probability of.

[0118] (41)

[0119] In the formula For signal amplitude, Let V be the variance of the noise signal. It is a zero-order Bessel function. The power is Therefore, the output signal-to-noise ratio of the envelope detector is

[0120] (42)

[0121] The Marcum Q function is defined as

[0122] (43)

[0123] Combining equations (18), (19), (20), and (21), the detection probability is rewritten as follows:

[0124] (44)

[0125] The detection probability expressions for CSK-LFM and LFM signals are the same because the output of the matched filter depends only on the signal energy and is independent of the specific form of the signal. Analysis of the detection probability expressions (19) and (22) shows that, with the false alarm probability remaining constant, the detection probability increases accordingly due to the increase in the signal-to-noise ratio.

[0126] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waveform optimization method integrating communication sensing for interference suppression, characterized in that: Includes the following steps: Step 1: The transmitter generates a basic pseudo-random noise (PRN) code and generates multiple CSK symbols through cyclic shifting. The CSK modulated signal uses a multi-level encoding method, which enables data bits to correspond to multiple different code sequences, thereby achieving signal modulation and obtaining modulated communication information data. Step 2: The transmitter uses an integrated CSK-LFM signal for waveform design. The LFM signal, as the waveform in the pulse radar system, improves the radar's range resolution and detection range without increasing peak power through pulse compression. The new integrated sensing waveform, formed by combining the CSK and LFM signals, is still a pulse waveform, with each pulse carrying a CSK signal and the LFM signal serving as the carrier of the CSK signal. The communication information data and PRN code generated in Step 1 are mapped using a multi-level method to obtain the CSK signal. Then, the LFM signal is used as the carrier to generate a CSK-LFM modulated signal that enters the channel. During demodulation, the intermediate frequency signal undergoes digital down-conversion, matched filtering, and selection of the optimal sampling point to obtain the baseband signal. The demodulated baseband signal is then demapped using CSK to output the communication data information. Step 3: The receiver receives the CSK-LFM integrated signal, performs digital signal processing on the integrated signal, calculates the communication bit error rate and bandwidth utilization, analyzes the bit error rate of the CSK-LFM integrated signal, converts the random communication data generated by the transmitter into analog signals through digital-to-analog conversion, transmits analog signals through the antenna, passes through an additive white Gaussian noise channel, the receiver receives the analog signals, performs analog-to-digital conversion, makes a decision on the digital signals, and calculates and compares the bit error rate of the CSK-LFM signal. Step 4: Use radar ambiguity functions to characterize the radar's resolution capabilities in both range and Doppler frequency shift dimensions; Ambiguity function and communication code metadata of CSK-LFM integrated signal and LFM carrier The first part is the autocorrelation function of the communication symbol, which is shaped like a thumbtack; the second part is equal to the ambiguity function of the classic LFM, which is shaped like a knife edge. Therefore, the ambiguity function of the integrated waveform is the superposition of the two shapes. Moreover, the ambiguity function based on the CSK-LFM integrated signal exhibits a thumbtack-like feature with low sidelobes and high main lobes, which improves the range and velocity resolution of the radar system. Step 5: The integrated backscattered signal received by the receiver passes through a matched filter and then undergoes envelope detection; the envelope detection output signal... The maximum value is sampled and used for decision-making; the system function of the matched filter is determined by the integrated CSK-LFM waveform. The radar detects target echoes in two states: with or without a target echo. A target echo is detected when the echo voltage exceeds a threshold voltage; otherwise, no target echo is detected. A false alarm occurs when no target echo enters the radar receiver, but the radar mistakes a noise signal for a target echo. A correct detection occurs when a target echo enters the radar receiver and is detected by the radar receiver. The false alarm probability... Receive signal in the presence of only noise The detected value exceeds the threshold voltage. The probability of detection is the same for CSK-LFM and LFM signals because the output of the matched filter depends only on the signal energy and is independent of the specific form of the signal. Analysis of the detection probability shows that, with the false alarm probability remaining constant, the detection probability increases accordingly due to the increase in the signal-to-noise ratio.

2. The integrated waveform optimization method for communication sensing for interference suppression as described in claim 1, characterized in that: The implementation method for step one is as follows: CSK(U,N) represents that each CSK symbol represents U bits of information, lasting for N CSK code cycles. The modulation principle of CSK is to map the U bits of message information that originally needed to be transmitted serially into different basic code sequences through cyclically shifted basic code sequences. Each cyclically shifted CSK symbol can carry U bits of information. The total number of independent waveforms generated after each round of basic code cyclic shift is... The CSK basic code is denoted as The i-th symbol of CSK is denoted as Where i = 0, 1, 2, ..., M-1, when the symbol period is equal to T and there are L chips, L is greater than or equal to M; the i-th cyclic shift version is represented as: (1) in: The integer representing the cyclic displacement of the i-th waveform. The duration of the chip interval, The code length of the basic code; the LFM signal is represented as: (2) (3) in, The amplitude; The frequency modulation slope is determined by the radar pulse duration T and bandwidth B, i.e. (4)。 3. The integrated waveform optimization method for communication sensing for anti-interference as described in claim 2, characterized in that: In step two, The CSK-LFM integrated communication sensing signal is represented as follows: (5) Where: the CSK basic code is denoted as The i-th symbol of CSK is denoted as The linear frequency modulated signal is denoted as , The integer representing the cyclic displacement of the i-th waveform. The duration of the chip interval, The code length of the base code, For carrier frequency.

4. The integrated waveform optimization method for communication sensing for interference suppression as described in claim 3, characterized in that: In step three, CSK stands for M-ary orthogonal signaling (MOS), and its vector representation is as follows: (6) The distance between any two signals is Send signal The received signal is obtained through the channel. (7) in: Indicates the signal amplitude. The mean is 0 and the variance is 0. Independent Gaussian random variables (8) send ,when When the receiver makes a correct decision, the probability of a correct decision is: (9) (10) According to equations (9) and (10), the probability of making an incorrect judgment is: (11) (12) in: Number in base 1 For spreading ratio, The amplitude attenuation coefficient caused by the Doppler frequency shift. The number of bits per symbol; the bandwidth utilization of CSK-LFM is... Where: N is the length of the code sequence, and each symbol can transmit Bit information, M is the number of available code patterns. B is the symbol rate, and B is the bandwidth.

5. The integrated waveform optimization method for communication sensing for interference suppression as described in claim 4, characterized in that: Step four is implemented as follows: Ambiguity function and communication code metadata of CSK-LFM integrated signal and LFM carrier Regarding Part One It is the autocorrelation function of the communication symbol, and its shape is thumbtack-shaped; the second part is equal to the fuzzy function of the classic LFM, and its shape is blade-shaped; the fuzzy function of the integrated waveform is the superposition of the two shapes, which can realize the dual functions of sensing and communication. The radar ambiguity function characterizes the radar's resolution capability in two dimensions: range and Doppler frequency shift. The radar ambiguity function is represented by the transmitted signal. The modulus of the two-dimensional cross-correlation function ; (13) in For time delay, For Doppler frequency shift, For signal conjugate; signal Divided into communication code metadata With LFM carrier The normalized complex envelope CSK-LFM signal is (14) Substituting equation (15) into equation (14), the CSK-LFM signal ambiguity function is: (15) In the formula: For communication code metadata conjugate, For linear frequency modulated carrier The conjugate of; Equation (15) is the product of two parts, the first part being The autocorrelation function, while the second part is the same as the traditional LFM fuzzy function; the second part is (16) Ambiguity function and communication code metadata of CSK-LFM integrated signal and LFM carrier Regarding Part One The first part is the autocorrelation function of the communication symbol, which is shaped like a thumbtack. The second part is equal to the ambiguity function of the classic LFM, which is shaped like a knife edge. The ambiguity function of the integrated waveform is the superposition of the two shapes, which can realize the dual functions of sensing and communication. The ambiguity function based on the CSK-LFM integrated signal presents a thumbtack-like feature with low sidelobes and high main lobes, which improves the range and velocity resolution of the radar system and is beneficial for low-altitude multi-target detection and tracking.

6. The integrated waveform optimization method for communication sensing for interference suppression as described in claim 5, characterized in that: Step five is implemented as follows: The receiver receives the backscattered integrated signal and passes it through the system function. After the matched filter, envelope detection is performed; the envelope detection output signal The maximum value is sampled and used for decision-making; the system function of the matched filter is determined by the integrated CSK-LFM waveform. Decision; False alarm probability Receive signal in the presence of only noise The detected value exceeds the threshold voltage. The probability of; (17) (18) Detection probability It is receiving signals The detected value exceeds the threshold voltage under conditions of added noise. The probability of; (19) In the formula For signal amplitude, Let V be the variance of the noise signal. It is a zero-order Bessel function. The power is Therefore, the output signal-to-noise ratio of the envelope detector is (20) The Marcum Q function is defined as (21) Combining equations (18), (19), and (20) with equation (21), the detection probability is rewritten as follows: (22) The detection probability expressions for CSK-LFM and LFM signals are the same because the output of the matched filter depends only on the signal energy and is independent of the specific form of the signal. From the expression (19) (22) of the detection probability, it can be seen that when the false alarm probability remains constant, the detection probability increases accordingly due to the increase in the signal-to-noise ratio.

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