阅读说明：本技术 基于时分多址的多用户通信雷达一体化系统 (Multi-user communication radar integrated system based on time division multiple access ) 是由 黄驿轩 胡苏� 叶启彬 胡泽林 于 2021-08-09 设计创作，主要内容包括：本发明属于通信雷达一体化技术领域,涉及一种基于时分多址的多用户通信雷达一体化系统。本发明按照时分原则,首先给用户分配不同发射时隙,每个用户在其发射时隙发射SC-FDE符号,在所有时隙进行雷达接收。在其所属发射时隙内,发送端先将待发送的二进制数据通过相位幅度调制或其他符号调制方式调制为数据符号,加循环前缀后发射入信道中。在接收端,将经过射频前端所得基带信号去CP后,再通过离散傅里叶变换、频域均衡和离散傅里叶逆变换得到数据符号,然后进行相应数据符号解调得到二进制数据。同时,其收发基带信号将被用于雷达处理以得到目标信息。该发明利用基于TDMA的SC-FDE有效实现具备较高数据率的多用户通信雷达一体化。(The invention belongs to the technical field of communication radar integration, and relates to a multi-user communication radar integrated system based on time division multiple access. According to the time division principle, different transmitting time slots are firstly allocated to users, each user transmits an SC-FDE symbol in the transmitting time slot, and radar reception is carried out in all the time slots. In the transmission time slot, the transmitting end firstly modulates binary data to be transmitted into data symbols through phase amplitude modulation or other symbol modulation modes, adds a cyclic prefix and then transmits the data symbols into a channel. At a receiving end, removing CP from a baseband signal obtained by a radio frequency front end, obtaining a data symbol through discrete Fourier transform, frequency domain equalization and inverse discrete Fourier transform, and then demodulating the corresponding data symbol to obtain binary data. Meanwhile, the transceiving baseband signals thereof are used for radar processing to obtain target information. The invention effectively realizes the integration of the multi-user communication radar with higher data rate by using SC-FDE based on TDMA.)

1. A multi-user communication radar integrated system based on time division multiple access is characterized in that a communication radar integrated (Radcom) platform is carried for each user, each platform transmits single carrier frequency domain equalization (SC-FDE) symbols only in a time slot to which the platform belongs, and the number of users is defined as N_uThe PAM modulation order is M, the SC-FDE basic symbol period is T, and the cyclic prefix period is T_cpThe number of PAM symbols transmitted by each SC-FDE symbol is N, and the period of the SC-FDE symbol is T_sym＝T+T_cpSampling rate of F_sN/T, with a sampling period of T_s＝T/N；

The data processing process of the transmitting terminal of the Radcom platform comprises the following steps:

s1, obtaining data symbol with length N after M-PAM modulation of the binary data transmitted by the ith user

S2, adding data symbols with length N_cpTo obtain a CP of length N + N_cpSC-FDE time domain transmission signal

At the same time, the user can select the desired position,is sent to a radar processing end to be used as a reference signal;

s3, after D/A conversion, when the platform belongs to the emitting time slot, the SC-FDE signal is emitted into the channel;

when the time slot is not the time slot to which the platform belongs, the data processing process of the Radcom platform communication receiving end is as follows:

s4, receiving the signal passing through the channel, removing CP after the signal passes through analog-to-digital conversion (A/D), and then mapping to the frequency domain by discrete Fourier transform through serial-to-parallel conversion (S/P) to obtain the frequency domain receiving signalPerforming frequency domain channel equalization to compensate for channel distortion, wherein the frequency domain equalization can adopt Minimum Mean Square Error (MMSE) equalization, Zero Forcing (ZF) equalization or Least Square (LS) equalization, and MMSE and ZF equalization coefficients are

Wherein, H [ k]Is a frequency domain representation of the channel impulse response, ε_bAnd N₀The power spectral density of the white additive gaussian noise and the energy per bit of the signal, respectively, the equalized signal is represented as an inverse discrete fourier transform of the multiplication of the frequency domain signal and the equalization coefficient:wherein IDFT (-) is an IDFT operation;

s5, performing parallel-to-serial conversion (P/S) and M-PAM symbol demodulation on the equalized signal to obtain binary data, namely finishing communication receiving processing;

the data processing process of the Radcom platform radar processing end is as follows:

s6, starting from the initial time slot of the platform transmission, i.e. assuming the time slot of the platform transmission as T e [0, T ∈_sym) For t e [0, N ] in the pulse repetition period_uT_sym) Is received by an echo signal of a sampling rate F_sAfter A/D of N/T, a length of N is obtained_u(N+N_cp) Of the discrete received signal

S7, using reference signalBased on the reference signal, performing sliding correlation operation with the discrete received signal y to extract the distance information of the environmental target to obtain a correlation vectorThe elements are

Wherein (·)^*Is a conjugate operation;

s8, adding N_fEach length is (N)_u-1)(N+N_cp) The +1 correlation vector z is arranged in a matrix form according to each z as a column, and the following matrix is obtained

For matrix M_zEach row of (1) is respectively performed with N_fPoint DFT operation to extract the relevant speed information of the environment target;

and S9, drawing a three-dimensional radar display image by the absolute value of the matrix element obtained in the step S8, and judging the number, the distance and the related speed information of the targets in the three-dimensional radar display image by using the preset threshold height, so that radar processing is completed.

Technical Field

The invention belongs to the technical field of Communication Radar integration (Radcom), and relates to a Multi-User Radcar and Communication (MU-Radcom) system based on Time Division Multiple Access (TDMA) Single Carrier Frequency Domain Equalization (SC-FDE).

Background

With the continuous development of science and technology, in order to meet the wireless requirements under the electromagnetic environment which is updated day by day, electronic equipment assembled on the same platform is increased gradually, so that the problems of system volume, energy consumption and weight increase, complex operation, increased redundancy, aggravated electromagnetic interference among equipment, system performance reduction and the like are caused. The adoption of a multifunctional integrated electronic system is an effective way for solving the problems, and the integration of communication radars is one of the most important development directions. The integration of the communication radar can be realized by a signal multiplexing mode and a signal fusion mode, and the signal fusion mode can realize that the radar and the communication share the same waveform and share system resources. The improved waveform based on SC-FDE is widely used as the uplink transmission waveform of the fourth generation mobile communication. While the traditional Pulse Doppler (PD) radar uses a Linear Frequency Modulation (LFM) signal, it cannot effectively load data. Meanwhile, how to realize multi-user communication and radar detection under networking conditions is still a difficult point of a communication radar integrated system. Therefore, multi-user implementation is a key technology to be solved urgently in the field of communication radar integration.

The multi-user communication radar integrated system based on the TDMA and the SC-FDE takes the SC-FDE as a transmitting waveform, adopts a stop/transmit system, and can regard an SC-FDE symbol as a transmitting pulse of a PD radar. And at a radar processing end, performing radar processing by using the transmitted SC-FDE symbol as a reference signal together with the echo signal, and finishing sensing the distance and the speed of the environmental target. Due to the special signal modulation mode of SC-FDE, the system can realize multi-user communication radar integration under the TDMA condition.

Disclosure of Invention

The invention aims to provide a MU-Radcom system based on TDMA and SC-FDE with higher data rate. Conventional SC-FDEs are not considered for radar detection, and conventional PD radars are not efficient for loading data. The invention provides a multi-user Radcom system based on TDMA and SC-FDE, which completes multi-user realization of the Radcom system by allocating user transmitting time slots under the condition of keeping higher communication data rate.

A schematic time-frequency structure diagram of a MU-RadCom waveform based on TDMA and SC-FDE is shown in fig. 1, where each user carries one RadCom platform, and each platform transmits an SC-FDE symbol only in its belonging time slot. Let the number of users be N_uThe order of Phase Amplitude Modulation (PAM) is M, the basic symbol period of SC-FDE is T, and the cyclic prefix period is T_cpAnd the number of PAM symbols transmitted by each SC-FDE symbol is N. The SC-FDE symbol period is T_sym＝T+T_cpSampling rate of F_sN/T, with a sampling period of T_sT/N. Fig. 2 shows a block diagram of a RadCom system based on TDMA and SC-FDE, where a data processing procedure at a transmitting end is as follows:

1) let the i-th user transmit binary data to obtain data symbol with length N after M-PAM modulation (or other symbol modulation mode)i＝0,1,...,N_u-1。

2) Adding data symbols with length N_cpTo avoid intersymbol interference, to obtain a length of N + N_cpSC-FDE time domain transmission signal

At the same time, the user can select the desired position,is sent to the radar processing end as a reference signal. Finally, after digital-to-analog conversion (D/A), the SC-FDE signal is transmitted into the channel when the platform belongs to the transmission time slot.

When the time slot is not the time slot to which the platform belongs, the data processing process of the Radcom platform communication receiving end is as follows:

1) firstly, receiving signals passing through a channel, removing CP (cyclic redundancy check) after the signals pass through analog-to-digital conversion (A/D), and then mapping the signals to a frequency domain by Discrete Fourier Transform (DFT) through serial-to-parallel conversion (S/P) to obtain frequency domain received signalsFrequency domain channel equalization is performed to compensate for channel distortion. The frequency domain equalization may employ Minimum Mean-Squared Error (MMSE) equalization, Zero Forcing (ZF) equalization, or Least Square (LS) equalization. MMSE and ZF equalization coefficients are respectively

Andwherein, H [ k]Is a frequency domain representation of the channel impulse response, ε_bAnd N₀The power spectral density of the signal per bit energy and Additive White Gaussian Noise (AWGN), respectively. The equalized signal may be represented as an Inverse Discrete Fourier Transform (IDFT) of the frequency domain signal multiplied by the equalization coefficients:n-0, 1.., N, where IDFT (·) is an IDFT operation.

2) And performing parallel-to-serial conversion (P/S) and M-PAM symbol demodulation (or other corresponding symbol demodulation modes) on the equalized signal to obtain binary data, namely finishing the communication receiving processing.

The data processing process of the Radcom platform radar processing end is as follows:

1) starting from the initial transmitting time slot of the platform, namely, assuming the transmitting time slot of the platform as T e [0, T ∈_sym) For t ∈ [0, N ] within a Pulse Repetition Interval (PRI)_uT_sym) Is received by an echo signal of a sampling rate F_sAfter A/D of N/T, a length of N is obtained_u(N+N_cp) Of the discrete received signal

2) Using reference signalsBased on the reference signal, performing sliding correlation operation with the discrete received signal y to extract the distance information of the environmental target to obtain a correlation vectorThe elements are

Wherein (·)^*Is a conjugate operation.

3) Will N_fEach length is (N)_u-1)(N+N_cp) The +1 correlation vector z is arranged in a matrix form according to each z as a column, and the following matrix is obtained

For matrix M_zEach row of (1) is respectively performed with N_fPoint DFT operation to extract relevant speed information of the environmental target.

4) And drawing a three-dimensional radar display image according to the absolute value of the matrix element obtained in the last step, and judging the number, distance and related speed information of the targets in the three-dimensional radar display image by using the preset threshold height, so as to finish radar processing.

The radar processing method adopted by the invention can detect the maximum distance r of the detectable target_max＝(N_u-1)T_symc/2, maximum relative velocity v_max＝c/(2f_cN_uT_sym) Whereinc and f_cThe distance resolution of the method is cT/(2N), the velocity resolution is c/(2N)_uN_ff_cT_sym)。

The invention has the beneficial effects that:

the invention provides a MU-Radcom system based on TDMA and SC-FDE on a traditional SC-FDE communication system and a traditional PD radar system. The method takes SC-FDE symbols as transmission pulses and completes multi-user realization through TDMA. The transmitting end of each user directly transmits the symbol data added with the CP into the channel in the transmitting time slot of each user. Except adding corresponding frequency domain equalization operation after removing CP, when the platform time slot is not the time slot of the communication receiving end, the data demodulation processing of the communication receiving end is the inverse operation of the transmitting end. And the radar processing firstly performs sliding correlation and then performs array processing by using the received signals in the pulse repetition period and the transmitted signals in the transmitting time slot to obtain the information of the number, the distance and the speed of the environmental targets. By adopting the MU-Radcom system based on TDMA and SC-FDE, respective radar detection and multi-user communication among networking users can be realized. Particularly, when the symbol modulation mode is PAM, the emission waveform of the symbol modulation mode is constant envelope, and the efficiency of the power amplifier can be greatly improved.

Drawings

FIG. 1 is a schematic diagram of a multi-user Radcom waveform time-frequency structure based on TDMA and SC-FDE (3 users).

FIG. 2 is a block diagram of a RadCom system based on TDMA and SC-FDE.

Detailed Description

The detailed technical solutions of the present invention have been described in the summary section, and the core contents of the present invention are summarized here.

At the transmitting end of Radcom platform, firstly, binary data is modulated and mapped into data symbols in the transmitting time slot to which the binary data belongs through PAM or other symbol modulation modes, and after CP is added, the obtained signals are divided into two paths: one path of signal is sent to a radar processing end to be used as a reference signal; and the other path of signal is transmitted to a channel through digital-to-analog conversion and an antenna to finish the transmission of the signal.

When the platform is not transmitting time slot, the communication receiving end of Radcom platform processes the signal received by antenna through A/D conversion, CP removal, serial-to-parallel conversion, DFT, frequency domain equalization, IDFT, parallel-to-serial conversion, and then demodulates PAM or other symbol modulation mode to obtain binary data, and completes communication receiving demodulation.

In the pulse repetition period, the radar processing end of the Radcom platform performs analog-to-digital conversion on the signals received by the antenna, and then sends the signals to the radar processing end for radar processing. In the Radcom system of the present invention, the local radar processing is based on sliding correlation of the transmitted and received signals and DFT array processing. Firstly, the received signal and the reference signal are subjected to sliding correlation, and then N is carried out_fArranging the obtained related vectors in a matrix form according to columns, and dividing the obtained matrix into rows to execute N_fAnd point DFT, and finally, drawing a three-dimensional radar display image by using the absolute values of the elements of the obtained matrix. According to the set threshold height, the number, the distance and the relative speed information of the environmental targets can be judged by the three-dimensional radar display image.