Detection and communication integrated waveform design method based on multi-sub-pulse time-polar domain joint modulation
Through the integrated waveform design of multi-sub pulse time polar domain joint modulation, the problems of low communication rate and difficult detection of high-speed targets in phased array detection are solved, and high communication rate and good Doppler tolerance are achieved.
Patent Information
- Application Number
- CN202510700932.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-28
- Publication Date
- 2025-08-26
AI Technical Summary
The detection based on phased array is the problem of low communication rate and difficulty in detecting high-speed targets in integrated waveform design.
The exploration-through integrated waveform design method of multi-sub pulse time polar domain joint modulation is adopted, and the communication information is embedded with the multi-sub pulse structure and polarization domain resources, and combined with time domain, frequency domain and airspace resource modulation, the exploration-through integrated waveform of multi-sub pulse time polar domain joint modulation is designed.
The communication rate is improved and the phenomenon that power at the target decays with the increase in speed during high-speed target detection is reduced, thereby enhancing Doppler tolerance.
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Figure CN120539715A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of phased array-based radar and communication integrated systems, and in particular relates to a sounding-through integrated waveform design method based on multi-sub-pulse time-domain joint modulation. Background Art
[0002] Currently, research on integrated sounding and communication waveform design is primarily divided into integrated sounding and communication waveform design with radar detection as its primary function and integrated sounding and communication waveform design with communication as its primary function. In integrated sounding and communication waveform design with radar detection as its primary function, the classic pulse Doppler system is often used to achieve communication information transmission while ensuring no or low loss in detection performance. Integrated sounding and communication waveform design with radar detection as its primary function is divided into integrated sounding and communication waveform design based on multiple-input multiple-output arrays and integrated sounding and communication waveform design based on phased arrays, depending on the antenna array. The former requires the design of multiple different waveforms equal to the number of antennas. The hardware complexity and system cost increase with the number of array elements. Therefore, many civilian and military radar systems still use phased array systems. Phased arrays only require the design of a single waveform, significantly reducing the system hardware complexity and cost. Therefore, research on integrated sounding and communication waveform design based on phased arrays has application value.
[0003] However, the existing integrated waveform design for detection-based sounding based on phased arrays generally has the problem of insufficient information embedding dimension and low communication rate. One type of design method transmits information by modulating the waveform parameters, for example: forming an integrated waveform by modulating the phase parameters of the classic linear frequency modulation waveform or modulating the sidelobe level of the beam pattern to transmit information. Another type is the integrated waveform design method based on optimization theory, which usually takes minimizing the peak sidelobe level of the autocorrelation function of the integrated sounding waveform as the criterion, considers different communication information modulation methods, establishes corresponding communication information modulation constraints, constructs the integrated sounding waveform optimization problem and solves it. Among them, the communication information modulation methods include: frequency zeroing modulation that uses the waveform frequency domain part to zero to transmit communication information, ambiguity function sidelobe zeroing modulation that uses the waveform ambiguity function sidelobe area part to zero to transmit communication information, and index modulation that uses the time domain phase and position of the waveform part to transmit information. The above methods respectively use the time domain, frequency domain and spatial domain resources of the waveform to embed communication information, but have not yet considered using the polarization domain resources of the waveform to embed communication information.
[0004] Furthermore, existing waveform designs for phased array-based detection systems are generally based on the classic pulse Doppler system. This poses the problem of rapid attenuation of power at the target as speed increases when detecting high-speed targets. To detect high-speed targets, research in radar waveform design has explored waveforms designed using multi-sub-pulse structures and radar signal processing methods based on single-pulse echoes. Summary of the Invention
[0005] In order to solve the problems of low communication rate and difficulty in high-speed target detection in the integrated waveform design of phased array detection, the present invention provides a sounding integrated waveform design method based on multi-sub-pulse time-domain joint modulation.
[0006] The present invention provides a sounding-through integrated waveform design method based on multi-sub-pulse time-domain joint modulation, comprising the following steps:
[0007] Step 1: Establish a sounding-through integrated polarization waveform model based on a multi-sub-pulse structure.
[0008] The co-located transmitter-receiver integrated sounding system consists of a transmitting / receiving phased uniform linear array composed of orthogonal electric dipoles parallel to the x-axis and y-axis, which contains M array elements with an array element spacing of d. It is assumed that the complex baseband waveform structure s(t) of the electromagnetic wave is composed of L orthogonal sub-pulse waveforms s1(t), s2(t), ..., s L (t) is composed of multiple sub-pulse waveforms, then the complex baseband waveform is s(t) and is expressed as:
[0009]
[0010] Where T0 is the sub-pulse duration, T=LT0 is the long pulse duration, and rect(t) is the rectangular window function, which is expressed as:
[0011]
[0012] Assuming that the sub-pulse waveform is a phase-encoded waveform, then s l (t) is expressed as:
[0013]
[0014] Among them, t b is the duration of the sub-chip, N is the number of sub-chips, a ln is the amplitude of the nth sub-chip of the lth phase-coded waveform, φ l (n) is the phase of the nth sub-chip of the lth phase-coded waveform.
[0015] Assume that the polarization mode of each sub-pulse waveform is different, where the lth sub-pulse waveform s l The polarization component of (t) is:
[0016]
[0017] where 0≤γ l ≤π is the polarization angle, -π≤η l ≤π is the polarization phase difference, and the waveform transmitted to the spatial orientation θ is expressed as:
[0018]
[0019] Where f0 is the carrier frequency, where a(θ)=[1 e -j2πdsinθ / λ … e -j2πd(M-1)sinθ / λ ] is the direction steering vector and ω is the weight vector.
[0020] Step 2: Multi-pulse time domain joint modulation and demodulation.
[0021] Among them, the polarization domain modulation in the polar domain communication information modulation of multiple sub-pulses is to modulate and demodulate the communication information by using the different polarization modes of the sub-pulse waveforms, specifically:
[0022] Select the polarization component set An element in is taken as the lth sub-pulse waveform s l The polarization component κ of (t) l , different selection methods represent different communication information, and the number of information bits transmitted within one pulse repetition interval is:
[0023] D1=Llog2P
[0024] Assume that the cooperative communication user space position is used as a parameter Expressed as, where θ is the pitch angle, The cooperative communication user receiving end is equipped with a pair of and The orthogonal electric dipole in the direction has the ability to receive polarized electromagnetic waves. The conversion relationship between the rectangular coordinate system and the spherical coordinate system is:
[0025]
[0026] After simple mathematical operations,
[0027] The waveform received by the cooperative communication user is expressed as:
[0028]
[0029] Among them, τ c represents the distance delay between the integrated transmitter and the communication user, β is the channel attenuation parameter, The variance is zero mean Additive white Gaussian noise.
[0030] Polarization domain demodulation is specifically as follows:
[0031] Sub-pulse division: using synchronization information to obtain the received waveform y c At the starting time of (t), the received waveform y is received according to the sub-pulse width T0. c (t) is divided into L sub-pulses to receive waveform yc1 (t),y c2 (t),…,y cL (t).
[0032] Calculating spatial orientation Polarization component set: Assuming the positions of cooperative communication users are known a priori Calculate the set of transmitted polarization components In spatial orientation The corresponding polarization component set in
[0033] Virtual polarization matching: receive waveform y for each sub-pulse cl (t), l=1,2,…,L virtual polarization matching, where the sub-pulse receiving waveform y cl (t) Each element in the conjugate transpose is then combined with the sub-pulse received waveform y cl (t) multiplied by each other, we can get
[0034] Energy selection detection: calculation Energy Select the polarization component corresponding to the maximum energy as the estimate of the transmitted polarization component Output the corresponding waveform y cl (t).
[0035] The time domain modulation in multi-pulse time domain communication information modulation is to transmit information by using different waveform arrangements. Assuming that the orthogonal waveform set is The integrated waveform of the multi-sub-pulse structure is a set of orthogonal waveforms The multi-pulse time domain modulation is a method of arranging the elements in the waveform to transmit information. The number of information bits transmitted within a pulse repetition interval is:
[0036]
[0037] Time-domain demodulation requires first performing polarization demodulation on the waveform within the sub-pulse. Then, each waveform in the orthogonal waveform set is used to perform matched filtering on each sub-pulse after virtual matching. The waveform with the largest peak value is selected as the current sub-pulse transmission waveform, and the arrangement of the sub-pulse waveforms is demodulated.
[0038] In summary, the number of information bits transmitted within one pulse repetition time of the multi-sub-pulse polar domain communication information modulation is:
[0039]
[0040] Step 3: Single pulse sounding integrated echo processing.
[0041] The target echo of the probe-through waveform within a pulse repetition time is expressed as:
[0042]
[0043] in, represents the target echo amplitude, τ r is the target delay, θ t is the target direction, represents additive white Gaussian noise, S represents the target scattering matrix, which is defined as:
[0044]
[0045] Considering the target is a uniform moving target, the target delay τ r =2(R0-vt) / c, where R0 is the initial radial distance of the target and v is the initial velocity of the target. The echo is expressed as:
[0046]
[0047] After receiving beamforming, we get:
[0048]
[0049] in, n r (t) is the noise component after beamforming.
[0050] The integrated echo processing of single pulse sounding with multi-sub-pulse time-polarity joint modulation is as follows:
[0051] Down-conversion of the integrated echo: Use exp(-j2πf0t) to convert the integrated echo y r (t) is down-converted to obtain the baseband echo:
[0052]
[0053] Where n′ r (t) is the noise component after down-conversion.
[0054] Virtual polarization matching of each sub-pulse waveform: Calculate the received polarization component r of each sub-pulse i =(Sκ i ) * ,i=1,2,…,L, use r i Virtual polarization matching echo, we get The specific expression is as follows:
[0055]
[0056] Where n r(t) is the noise component after virtual polarization matching.
[0057] Matched filtering: use s1(t),s2(t),…,s L (t) The waveform after the corresponding matched filter matches the virtual polarization Perform matched filtering and we can get Right now:
[0058]
[0059] in, is the amplitude after matched filtering, For s l (autocorrelation function of t0, is the Doppler frequency, n″′ r (t) is the noise component after matched filtering.
[0060] Range gate alignment: Shift the l=2, 3…, Lth sub-pulse filtering results to the left by cT0(l-1) / 2 meters so that the L sub-pulse filtering results are aligned with the range gate where the target is located.
[0061] Zero padding: Pad the matched filter result after the range gate alignment and shift processing to obtain Make each filtering result restored to the length of the matched filtering processing result.
[0062] Moving target detection processing: The matched filtering results obtained after zero padding are processed for moving target detection to obtain target speed information. The specific steps are as follows:
[0063] Assuming that the distance resolution unit is ΔR and the target movement speed satisfies vT0≤ΔR, the envelope of the above formula changes slowly with respect to the target speed v. Based on the "stop-jump" assumption of the radar system, the above formula is approximately:
[0064]
[0065] in For s l The second exponential term is the discrete sampling of the complex sine wave with a frequency of 2vf0 / c. The 2vf0 / c, that is, the Doppler frequency, is obtained by Fourier transform, and then the target speed is obtained.
[0066] The beneficial technical effects of the present invention are:
[0067] This invention, for the first time, applies joint time-domain and polarization-domain modulation techniques to the design of an integrated sounding waveform based on a multi-subpulse structure. This utilizes the waveform's time-domain and polarization-domain resources to modulate communication information, enabling integration with existing frequency-domain and spatial-domain communication information modulation methods to further increase communication rates. Furthermore, the multi-subpulse structure, inspired by existing radar waveform designs, ensures that the designed integrated waveform possesses excellent Doppler tolerance. Compared to integrated sounding waveforms designed based on pulse Doppler systems, this design achieves lower power attenuation at high-speed targets as speed increases. BRIEF DESCRIPTION OF THE DRAWINGS
[0068] Figure 1 Schematic diagram of the integrated research scenario.
[0069] Figure 2 Schematic diagram of the complex baseband waveform of the multi-sub-pulse structure.
[0070] Figure 3 Schematic diagram of multi-sub-pulse time-domain joint modulation.
[0071] Figure 4 Schematic diagram of multi-pulse polarization domain demodulation.
[0072] Figure 5 Schematic diagram of multi-pulse time domain demodulation.
[0073] Figure 6 It is a single pulse sounding integrated echo processing process.
[0074] Figure 7 Schematic diagram of frequency domain zero modulation.
[0075] Figure 8 is the variation of bit error rate with signal-to-noise ratio.
[0076] Figure 9 Doppler tolerance analysis.
[0077] Figure 10 This is the result of single-pulse sounding integrated echo processing.
[0078] Figure 11 This is the result of integrated echo processing when the speeds are different. DETAILED DESCRIPTION
[0079] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0080] The present invention provides a sounding-through integrated waveform design method based on multi-sub-pulse time-domain joint modulation, comprising the following steps:
[0081] Step 1: Establish a sounding-through integrated polarization waveform model based on a multi-sub-pulse structure.
[0082] The present invention is applicable to the integrated system of transmitting and receiving at the same time as the detection and communication Figure 1 As shown in the figure, the system consists of a uniform linear array of transmit / receive phased arrays parallel to the x-axis and y-axis, consisting of M array elements with an array element spacing of d. Assume that the complex baseband waveform structure s(t) of the electromagnetic wave is as follows: Figure 2 As shown, it is composed of L orthogonal sub-pulse waveforms s1(t), s2(t0,…,s L (t) is composed of multiple sub-pulse waveforms, then the complex baseband waveform is s(t) and is expressed as:
[0083]
[0084] Where T0 is the sub-pulse duration, T=LT0 is the long pulse duration, and rect(t) is the rectangular window function, which is expressed as:
[0085]
[0086] Assuming that the sub-pulse waveform is a phase-encoded waveform, then s l (t) is expressed as:
[0087]
[0088] Among them, t b is the duration of the sub-chip, N is the number of sub-chips, a ln is the amplitude of the nth sub-chip of the lth phase-coded waveform, φ l (n) is the phase of the nth sub-chip of the lth phase-coded waveform.
[0089] Assume that the polarization mode of each sub-pulse waveform is different, where the lth sub-pulse waveform s l The polarization component of (t) is:
[0090]
[0091] where 0≤γ l ≤π is the polarization angle, -π≤η l ≤π is the polarization phase difference, and the waveform transmitted to the spatial orientation θ is expressed as:
[0092]
[0093] Where f0 is the carrier frequency, where a(θ)=[1 e -j2πdsinθ / λ … e -j2πd(M-1)sinθ / λ ] is the direction steering vector and ω is the weight vector.
[0094] Step 2: Multi-pulse time domain joint modulation and demodulation.
[0095] Among them, the polarization domain modulation in the polar domain communication information modulation of multiple sub-pulses uses the different modulation and demodulation modes of the sub-pulse waveform polarization to modulate and demodulate the communication information. The modulation diagram is shown in the figure. Figure 3 As shown, specifically:
[0096] Select the polarization component set An element in is taken as the lth sub-pulse waveform s l The polarization component κ of (t) l , different selection methods represent different communication information, and the number of information bits transmitted within one pulse repetition interval is:
[0097] D1=Llog2P
[0098] Assume that the cooperative communication user space position is used as a parameter Expressed as, where θ is the pitch angle, The cooperative communication user receiving end is equipped with a pair of and The orthogonal electric dipole in the direction has the ability to receive polarized electromagnetic waves. The conversion relationship between the rectangular coordinate system and the spherical coordinate system is:
[0099]
[0100] After simple mathematical operations,
[0101] The waveform received by the cooperative communication user is expressed as:
[0102]
[0103] Among them, τ c represents the distance delay between the integrated transmitter and the communication user, β is the channel attenuation parameter, The variance is zero mean Additive white Gaussian noise.
[0104] Polarization domain demodulation Figure 4 As shown, specifically:
[0105] Sub-pulse division: using synchronization information to obtain the received waveform y c At the starting time of (t), the received waveform y is received according to the sub-pulse width T0. c (t) is divided into L sub-pulses to receive waveform y c1 (t),y c2 (t),…,y cL (t).
[0106] Calculating spatial orientation Polarization component set: Assuming the positions of cooperative communication users are known a priori Calculate the set of transmitted polarization components In spatial orientation The corresponding polarization component set in
[0107] Virtual polarization matching: receive waveform y for each sub-pulse cl (t), l=1,2,…,L virtual polarization matching, where the sub-pulse receiving waveform y cl (t) Each element in the conjugate transpose is then combined with the sub-pulse received waveform y cl (t) multiplied by each other, we can get
[0108] Energy selection detection: calculation Energy Select the polarization component corresponding to the maximum energy as the estimate of the transmitted polarization component Output the corresponding waveform y cl (t).
[0109] The time domain modulation in multi-pulse time domain communication information modulation uses different waveform arrangements to transmit information. The modulation diagram is shown in the figure. Figure 3 As shown, assuming that the orthogonal waveform set is The integrated waveform of the multi-sub-pulse structure is a set of orthogonal waveforms The multi-pulse time domain modulation is a method of arranging the elements in the waveform to transmit information. The number of information bits transmitted within a pulse repetition interval is:
[0110]
[0111] Time domain demodulation requires first performing polarization demodulation on the waveform within the sub-pulse, and then using each waveform in the orthogonal waveform set to perform matched filtering on each sub-pulse after virtual matching, selecting the one with the largest peak as the current sub-pulse emission waveform, and then demodulating the arrangement of the sub-pulse waveforms. The schematic diagram of time domain demodulation is shown in the figure below. Figure 5 shown.
[0112] In summary, the number of information bits transmitted within one pulse repetition time of the multi-sub-pulse polar domain communication information modulation is:
[0113]
[0114] Step 3: Single pulse sounding integrated echo processing.
[0115] The target echo of the probe-through waveform within a pulse repetition time is expressed as:
[0116]
[0117] in, represents the target echo amplitude, τ r is the target delay, θ t is the target direction, represents additive white Gaussian noise, S represents the target scattering matrix, which is defined as:
[0118]
[0119] Considering the target is a uniform moving target, the target delay τ r =2(R0-vt) / c, where R0 is the initial radial distance of the target and v is the initial velocity of the target. The echo is expressed as:
[0120]
[0121] After receiving beamforming, we get:
[0122]
[0123] in, n r (t) is the noise component after beamforming.
[0124] The integrated echo processing flow of single pulse sounding with multi-sub-pulse time-polarity joint modulation is as follows: Figure 6 As shown, specifically:
[0125] Down-conversion of the integrated echo: Use exp(-j2πf0t) to convert the integrated echo y r (t) is down-converted to obtain the baseband echo:
[0126]
[0127] Where n′ r (t) is the noise component after down-conversion.
[0128] Virtual polarization matching of each sub-pulse waveform: Calculate the received polarization component r of each sub-pulse i =(Sκ i ) * ,i=1,2,…,L, use r i Virtual polarization matching echo, we get The specific expression is as follows:
[0129]
[0130] Where n r (t) is the noise component after virtual polarization matching.
[0131] Matched filtering: use s1(t),s2(t),…,sL (t) The waveform after the corresponding matched filter matches the virtual polarization Perform matched filtering and we can get Right now:
[0132]
[0133] in, is the amplitude after matched filtering, For s l The autocorrelation function of (t), is the Doppler frequency, n″′ r (t) is the noise component after matched filtering.
[0134] Range gate alignment: Shift the l=2, 3…, Lth sub-pulse filtering results to the left by cT0(l-1) / 2 meters so that the L sub-pulse filtering results are aligned with the range gate where the target is located.
[0135] Zero padding: Pad the matched filter result after the range gate alignment and shift processing to obtain Make each filtering result restored to the length of the matched filtering processing result.
[0136] Moving target detection processing: The matched filtering results obtained after zero padding are processed for moving target detection to obtain target speed information. The specific steps are as follows:
[0137] Assuming that the distance resolution unit is ΔR and the target movement speed satisfies vT0≤ΔR, the envelope of the above formula changes slowly with respect to the target speed v. Based on the "stop-jump" assumption of the radar system, the above formula is approximately:
[0138]
[0139] in For s l The second exponential term is the discrete sampling of the complex sine wave with a frequency of 2vf0 / c. The 2vf0 / c, that is, the Doppler frequency, is obtained by Fourier transform, and then the target speed is obtained.
[0140] Compared to the traditional pulse Doppler radar echo model, the number of sub-pulses is equivalent to the number of pulses within one coherent processing time of the pulse Doppler radar. Therefore, moving target detection can be achieved within a single pulse echo rather than within the coherent processing time, which greatly reduces the target observation time required for moving target detection.
[0141] Compared with the existing single-pulse radar echo processing method, the single-pulse sounding integrated echo signal processing process proposed in the present invention adds a virtual polarization matching step for each sub-pulse waveform.
[0142] The single-pulse sounding integrated echo processing method is sub-pulse matched filtering. When the sub-pulse waveform reaches the first zero point of the zero-delay intercept of the ambiguity function, the Doppler frequency becomes L times that of the traditional waveform, thereby improving the Doppler tolerance of the designed waveform. Compared with traditional pulse Doppler radar echo processing, the power at the target attenuates more slowly with increasing speed, which is conducive to high-speed target detection.
[0143] Example 1:
[0144] Table 1 shows the communication rate of the integrated waveform designed by the multi-pulse time polarization modulation (TPM) proposed in the present invention under typical parameter settings. For comparative analysis, the communication rate of the integrated waveform designed based on the existing frequency nulling modulation (FNM) technology is given, as well as the communication rate of the integrated waveform designed by the TPM combined with FNM proposed in the present invention, which is named time frequency polarization modulation (TFPM).
[0145] Table 1 Communication rate under some typical parameters (1 PRT time)
[0146] Serial number Parameter settings TPM FNM TFPM ① <![CDATA[L=8,P=8,F num =40]]> 39 40 79 ② <![CDATA[L=16,P=8,F num =40]]> 92 40 132 ③ <![CDATA[L=8,P=16,F num =40]]> 47 40 87 ④ <![CDATA[L=8,P=8,F num =80]]> 39 80 119
[0147] The principle of the integrated sounding waveform designed based on the existing FNM technology is as follows:
[0148] By setting the sub-band of the integrated waveform as the communication sub-band, when the communication sub-band is the passband, the information bit 0 is transmitted, and when the communication sub-band is the stopband, the information bit 1 is transmitted. The modulation diagram is shown as follows Figure 7 At the communication receiving end, the communication sub-band is identified as a channel or a stop band based on the energy size detection, thereby realizing the demodulation of the information. Assuming that the total number of FNM modulation communication sub-band variables is F num When designing an integrated waveform based on TFPM, FNM is used to design each sub-pulse waveform.
[0149] Table 1 shows the communication rates of the integrated waveforms based on the TPM proposed in the present invention and the FNM and TFPM designs. It can be seen that the integrated waveform of the TPM design proposed in the present invention increases with the increase of the number of sub-pulses L and the set of transmitted polarization components. As the cardinality P increases, the communication rate increases, and the impact of the number of subpulses is greater than the cardinality of the transmitted polarization components. Combining TFPM modulation with existing FNM technology to design a sounding-integrated waveform can further increase the communication rate.
[0150] Example 2:
[0151] Figure 8 Given the parameters L=8,P=8,F num =40, the bit error rate (SER) of the integrated waveform designed based on TPM, FNM, and TFPM varies with the signal to noise ratio (SNR). It can be seen that the SER performance of the integrated waveform based on TPM proposed in the present invention is better than that of the integrated waveform based on FNM. When the two methods are jointly modulated, that is, TFPM, the SER performance of the integrated waveform is greatly affected by FNM.
[0152] Example 3:
[0153] Figure 9 Given the parameters L=8,P=8,F num =40, the Doppler tolerance analysis of the integrated waveform designed based on TPM, FNM, and TFPM is shown in the first three figures. The ambiguity function of the integrated waveform designed based on TPM, FNM, and TFPM is shown. It can be obtained that the position of the first zero point of the zero-delay intercept of the ambiguity function of the integrated waveform designed based on the existing FNM technology is 1 / T, while the position of the first zero point of the zero-delay intercept of the ambiguity function of the integrated waveform designed based on TPM proposed in the present invention is 1 / T0, which is consistent with the theoretical analysis. When the ambiguity function characteristics of the integrated waveform designed with TFPM combining FNM and TPM are basically the same as those of the integrated waveform designed based on TPM. The last figure shows the change of the peak sidelobe level (PSL) of the autocorrelation function of the above waveform with Doppler mismatch. The PSL of the integrated waveform designed based on FNM oscillates and increases with the increase of Doppler mismatch, while the PSL of the integrated waveform designed based on TPM proposed in the present invention increases slowly with the increase of speed. The reason is that the position of the first zero point of the zero-delay intercept of the ambiguity function based on the FNM integrated waveform is smaller than the position of the first zero point based on the TPM integrated waveform. Therefore, the TPM-based integrated waveform proposed in the present invention has better Doppler tolerance than the FNM-based integrated waveform.
[0154] Example 4:
[0155] Figure 10 The simulation results of the integrated waveform designed based on TPM and the proposed single-pulse sounding integrated echo processing flow are given, which show that the target range and speed can be accurately estimated by processing the single-pulse echo.
[0156] Example 5:
[0157] Figure 11The results of single-pulse sounding integrated echo processing using integrated waveforms designed based on FNM and TPM are presented for detecting targets at different speeds. Since the integrated waveform designed based on the existing FNM technology uses a classic pulse Doppler system, single-pulse sounding integrated echo processing can only estimate the target range. However, since the integrated waveform designed based on TPM uses a multi-sub-pulse structure, combined with the proposed single-pulse sounding integrated echo processing method, single-pulse echo processing can accurately estimate the target range and speed.
[0158] In addition, as the target speed increases, the peak power at the target after pulse compression of the integrated waveform designed based on the existing FNM technology decreases as the speed increases, while the peak power at the target of the integrated waveform designed based on the TPM technology remains almost consistent as the target speed increases. This is because the integrated waveform designed based on the TPM technology has a higher Doppler tolerance than the integrated waveform designed based on the FNM technology. For a specific analysis, see Example 3.
Claims
1. A sounding-through integrated waveform design method based on multi-sub-pulse time-domain joint modulation, characterized in that: The following steps are involved: Step 1: Establish a polarization waveform model based on a multi-sub-pulse structure; The co-located transmitter-receiver integrated sounding system consists of a transmitting / receiving phased uniform linear array composed of orthogonal electric dipoles parallel to the x-axis and y-axis, which contains M array elements with an array element spacing of d. It is assumed that the complex baseband waveform structure s(t) of the electromagnetic wave is composed of L orthogonal sub-pulse waveforms s1(t), s2(t), ..., s L (t) is composed of multiple sub-pulse waveforms, then the complex baseband waveform is s(t) and is expressed as: Where T0 is the sub-pulse duration, T=LT0 is the long pulse duration, and rect(t) is the rectangular window function, which is expressed as: Assuming that the sub-pulse waveform is a phase-encoded waveform, then s l (t) is expressed as: Among them, t b is the duration of the sub-chip, N is the number of sub-chips, a ln is the amplitude of the nth sub-chip of the lth phase-coded waveform, φ l (n) is the phase of the nth sub-chip of the lth phase-coded waveform; Assume that the polarization mode of each sub-pulse waveform is different, where the lth sub-pulse waveform s l The polarization component of (t) is: where 0≤γ l ≤π is the polarization angle, -π≤η l ≤π is the polarization phase difference, and the waveform transmitted to the spatial orientation θ is expressed as: Where f0 is the carrier frequency, where a(θ)=[1e -j2πdsinθ / λ …e -j2πd(M-1)sinθ / λ ] is the direction vector, ω is the weight vector; Step 2: Multi-sub-pulse time domain joint modulation and demodulation; Among them, the polarization domain modulation in the polar domain communication information modulation of multiple sub-pulses is to modulate and demodulate the communication information by using the different polarization modes of the sub-pulse waveforms, specifically: Select the polarization component set An element in is taken as the lth sub-pulse waveform s l The polarization component κ of (t) l , different selection methods represent different communication information, and the number of information bits transmitted within one pulse repetition interval is: D1=Llog2P Assume that the cooperative communication user space position is used as a parameter Expressed as, where θ is the pitch angle, The cooperative communication user receiving end is equipped with a pair of and The orthogonal electric dipole in the direction has the ability to receive polarized electromagnetic waves. The conversion relationship between the rectangular coordinate system and the spherical coordinate system is: After simple mathematical operations, The waveform received by the cooperative communication user is expressed as: Among them, τ c represents the distance delay between the integrated transmitter and the communication user, β is the channel attenuation parameter, The variance is zero mean Additive Gaussian white noise; Polarization domain demodulation is specifically as follows: Sub-pulse division: using synchronization information to obtain the received waveform y c At the starting time of (t), the received waveform y is received according to the sub-pulse width T0. c (t) is divided into L sub-pulses to receive waveform y c1 (t),y c2 (t),…,y cL (t); Calculating spatial orientation Polarization component set: Assuming the positions of cooperative communication users are known a priori Calculate the set of transmitted polarization components In spatial orientation The corresponding polarization component set in Virtual polarization matching: receive waveform y for each sub-pulse cl (t), l=1,2,…,L virtual polarization matching, where the sub-pulse receiving waveform y cl (t) Each element in the conjugate transpose is then combined with the sub-pulse received waveform y cl (t) multiplied by each other, we can get Energy selection detection: calculation Energy Select the polarization component corresponding to the maximum energy as the estimate of the transmitted polarization component Output the corresponding waveform y cl (t); The time domain modulation in multi-pulse time domain communication information modulation is to transmit information by using different waveform arrangements. Assuming that the orthogonal waveform set is The integrated waveform of the multi-sub-pulse structure is a set of orthogonal waveforms The multi-pulse time domain modulation is a method of arranging the elements in the waveform to transmit information. The number of information bits transmitted within a pulse repetition interval is: Time-domain demodulation requires first performing polarization demodulation on the waveform within the sub-pulse. Then, each waveform in the orthogonal waveform set is used to perform matched filtering on each sub-pulse after virtual matching. The waveform with the largest peak value is selected as the current sub-pulse transmission waveform, and the arrangement of the sub-pulse waveforms is then demodulated. In summary, the number of information bits transmitted within one pulse repetition time of the multi-sub-pulse polar domain communication information modulation is: Step 3: Single pulse sounding integrated echo processing; The target echo of the probe-through waveform within a pulse repetition time is expressed as: in, represents the target echo amplitude, τ r is the target delay, θ t is the target direction, represents additive white Gaussian noise, S represents the target scattering matrix, which is defined as: Considering the target is a uniform moving target, the target delay τ r =2(R0-vt) / c, where R0 is the initial radial distance of the target and v is the initial velocity of the target. The echo is expressed as: After receiving beamforming, we get: in, n r (t) is the noise component after beamforming; The integrated echo processing of single pulse sounding with multi-sub-pulse time-polarity joint modulation is as follows: Down-conversion of the integrated echo: Use exp(-j2πf0t) to convert the integrated echo y r (t) is down-converted to obtain the baseband echo: Where n′ r (t) is the noise component after down-conversion; Virtual polarization matching of each sub-pulse waveform: Calculate the received polarization component r of each sub-pulse i =(Sκ i ) * ,i=1,2,…,L, use r i Virtual polarization matching echo, we get The specific expression is as follows: Where n r (t) is the noise component after virtual polarization matching; Matched filtering: use s1(t),s2(t),…,s L (t) The waveform after the corresponding matched filter matches the virtual polarization Perform matched filtering and we can get Right now: in, is the amplitude after matched filtering, For s l The autocorrelation function of (t), is the Doppler frequency, n″′ r (t) is the noise component after matched filtering; Range gate alignment: Shift the filtering results of the l=2, 3…, L sub-pulses to the left by cT0(l-1) / 2 meters so that the L sub-pulse filtering results are aligned with the range gate where the target is located; Zero padding: Pad the matched filter result after the range gate alignment and shift processing to obtain Make each filtering result restored to the length of the matched filtering processing result; Moving target detection processing: The matched filtering results obtained after zero padding are processed for moving target detection to obtain target speed information. The specific steps are as follows: Assuming that the range resolution unit is ΔR and the target speed satisfies vT0≤ΔR, the envelope of the above formula changes slowly with respect to the target speed v. Based on the "stop-jump" assumption of the radar system, the above formula is approximately: in For s l The second exponential term is the discrete sampling of the complex sine wave with a frequency of 2vf0 / c. The 2vf0 / c, that is, the Doppler frequency, is obtained by Fourier transform, and then the target speed is obtained.