Radar interference angle measurement method based on coherent MIMO signal processing

Abstract

The invention discloses a radar interference angle measurement method based on coherent MIMO signal processing, relates to the field of radar signal processing, and mainly solves the problem of improving the detection precision of an interference measurement system in radar signal processing. The method comprises the following steps of: 1, determining basic parameters of a system, wherein the basic parameters comprise position coordinates of two measuring stations, an interference measurement baseline, two groups of orthogonal waveform designs and a signal carrier frequency; 2, the measurement station carries out two groups of matched filtering processing on the received signals; and 3, performing equivalent transmitting beam forming processing on the two groups of matched filtering results of each receiving station. 4, respectively taking out the phases Phi1 and Phi2 of the synthesized signals R1 and R2 of the two measuring stations, and calculating the phase difference dPhii between the two measuring stations according to a formula dPhii = Phi1-Phi2; and 5, target angle calculation is carried out based on the phase difference dPhi between the two measurement stations. According to the invention, the signal-to-noise ratio of the received signal is improved based on coherent MIMO signal processing, the problem that the interference measurement precision is limited under the condition of low signal-to-noise ratio is solved, and the angle measurement precision is improved.

Description

Technical Field

[0001] The present invention relates to the field of radar signal processing, and is particularly applicable to a radar interference angle measurement method based on coherent MIMO (multiple-input multiple-output) signal processing. Background Art

[0002] The radar interferometry angle measurement algorithm uses the signal phase difference between two separate radar receiving stations to solve the angle between the target and the measurement baseline. It has high-precision measurement capabilities and has been widely used in the fields of high-orbit and low-orbit target measurement, low-speed and small target measurement, etc. However, in a low signal-to-noise ratio environment, the target phase measurement is affected, which is more likely to cause phase ambiguity, seriously affecting the accuracy of interferometry angle measurement. CN201810488689.5 proposes a continuous wave radar phase interference angle measurement method based on receiving channel multiplexing, which controls multiple independent receiving channels through a splitter, receives signals in the form of time division multiplexing, and performs phase-locked tracking and segmented integration on the receiving signals of each independent channel, and then restores them to continuous wave signals for high-precision measurement. Although this method can have high interference angle measurement accuracy in a low signal-to-noise ratio environment, it is complex to implement and requires additional splitters and multi-channel signal joint processing methods, which increases hardware and software resource overhead; the document "Low Signal-to-Noise Ratio Dual-Base MIMO Radar Target Angle Tracking Algorithm" proposes a target angle measurement and tracking algorithm based on improved AAJD (Adaptive Asymmetric JointDiagonalization), which solves the problem of signal subspace expansion of the AAJD algorithm at low signal-to-noise ratio, but this method requires calculation of eigenvalues ​​and signal subspace operations, and is complex to implement and requires more software and hardware computing resources; CN202211303169.5 A two-dimensional interferometric angle measurement method based on spatial geometric relationship constraints is proposed in this paper. Multiple phase differences are collected by antenna arrays, and phase defuzzification is performed based on spatial geometric constraint functions to obtain the optimal path difference combination of multiple baselines. This method can obtain the optimal angle solution by jointly solving multiple baselines, but this method will be seriously affected in low signal-to-noise ratio environments. Therefore, the radar interferometric angle measurement method based on coherent MIMO signal processing has important research significance. Summary of the invention

[0003] The purpose of the present invention is to provide a radar interferometry angle measurement method based on coherent MIMO signal processing to solve the above problems. The method constructs a coherent MIMO radar interferometry angle measurement model by transmitting orthogonal signals from the measuring stations. Coherent MIMO signal processing is used to improve the signal-to-noise ratio of the received signal, solve the problem of limited radar interferometry measurement accuracy under low signal-to-noise ratio conditions, and improve the angle measurement accuracy.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A radar interferometry angle measurement method based on coherent MIMO signal processing comprises the following steps: Step 1: Determine the basic parameters of the system, including the position coordinates of the two measuring stations, the interferometric measurement baseline, two sets of orthogonal waveform designs and signal carrier frequency; Step 2: The two measuring stations transmit orthogonal pseudo code signals respectively. The signals reach the two measuring stations after being reflected by the target. Each measuring station performs correlation operation on the received signals and the matched filters corresponding to the two sets of orthogonal waveforms to obtain two sets of matched filtering results. Step 3: Calculate the phase compensation value p of the two transmission channels according to the current measurement station antenna pointing direction and the measurement baseline length. 1 and p 2 Then, the two sets of matched filtering results of each measuring station are processed with equivalent transmit beam synthesis corresponding to the phase compensation values ​​of the two transmit channels. Step 4: respectively obtain the phases of the beamformed signals of the two measuring stations and calculate the phase difference between the two measuring stations; Step 5: Calculate the target angle based on the phase difference between the two measurement stations.

[0005] Compared with the background technology, the present invention has the following beneficial effects: The interference angle measurement of the present invention has high accuracy. Based on MIMO signal processing, the signal-to-noise ratio of the received signal of the measuring station is improved, thereby reducing the influence of noise on the signal phase, and improving the accuracy of radar interference angle measurement. Taking the carrier frequency of 1GHz, the baseline length of 1m, and the signal-to-noise ratio of 15dB as an example, the angle measurement accuracy of the traditional interference angle measurement method is 0.9214 degrees. Under the same conditions, this method can increase the signal-to-noise ratio by 3dB to 18dB, and reduce the angle measurement error to 0.8411 degrees. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a flow chart of radar interferometry angle measurement based on coherent MIMO signal processing implemented in the present invention.

[0007] Figure 2 It is a schematic diagram of a working scenario of an embodiment of the present invention. DETAILED DESCRIPTION

[0008] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0009] Reference Figure 1 , follow the following process to complete the radar interferometry angle measurement method based on coherent MIMO signal processing. The working scenario is shown as follows Figure 2 .

[0010] Step 1: Determine the basic parameters of the system, including the position coordinates of the two measurement stations, the interferometric measurement baseline, two sets of orthogonal waveform designs and signal carrier frequency.

[0011] First, determine the positions of the two transmitting and receiving measurement stations, denoted as Pos1 and Pos2 respectively. The center distance between the two measurement stations is 1m, and an interferometric angle measurement system with a baseline length of 1m is obtained. Then, the signal carrier frequency is set to 1 GHz, and the signal waveform adopts orthogonal binary code.

[0012] Step 2: Filter the received signal.

[0013] First, the two measuring stations transmit orthogonal pseudo codes respectively. The signals are reflected by the target and reach the two measuring stations. The received signals of the two stations are recorded as R 1 and R 2 ; Then, the received signal is filtered and the received signal of each measuring station is filtered by the matched filter H corresponding to the two sets of orthogonal waveforms. 1 and H 2 Perform convolution related operations; Finally, each measuring station will obtain two sets of matched filtering results, namely R 1 H 1 , R 1 H 2 and R 2 H 1 , R 2 H 2 .

[0014] Step 3: Equivalent transmit beam synthesis.

[0015] First, the phase compensation value p of the two transmission channels is calculated according to the current measurement station antenna pointing alpha and the measurement baseline length d. 1 and p 2 , taking station 1 as the reference center, then p 1 =0, p 2 =d*sin(alpha); Then, the two sets of matched filtering results of each measuring station are processed by equivalent transmit beam synthesis, and the phase compensation values ​​of the two transmit channels are weighted with the corresponding matched filtering results. 1和 =R 1 H 1 *exp(-i*p 1 )+R 1 H 2 *exp(-i*p 2 ), R 2和 =R 2 H 1 *exp(-i*p 1 )+ R 2 H 2 *exp(-i*p 2 ); Finally, the synthesized signals are R 1和 and R 2和 .

[0016] Step 4: Take out the beamformed signals R of the two measurement stations respectively 1和 and R 2和 Phase Phi 1 and Phi 2 , calculate the phase difference between the two measuring stations dPhi = Phi 1 -Phi 2 .

[0017] Step 5: Calculate the target angle based on the phase difference dPhi between the two measuring stations.

Claims

1. A radar interferometry angle measurement method based on coherent MIMO signal processing, characterized in that: The following steps are involved: Step 1: Determine the basic parameters of the system, including the position coordinates of the two measuring stations, the interferometric measurement baseline, two sets of orthogonal waveform designs and signal carrier frequency; Step 2: The two measuring stations transmit orthogonal pseudo code signals respectively. The signals reach the two measuring stations after being reflected by the target. Each measuring station performs correlation operation on the received signals and the matched filters corresponding to the two sets of orthogonal waveforms to obtain two sets of matched filtering results. Step 3: Calculate the phase compensation values ​​p1 and p2 of the two transmit channels according to the current measurement station antenna pointing direction and the measurement baseline length, and then perform equivalent transmit beamforming processing on the two sets of matched filtering results of each measurement station corresponding to the phase compensation values ​​of the two transmit channels. Step 4: respectively obtain the phases of the beamformed signals of the two measurement stations and calculate the phase difference between the two measurement stations; Step 5: Calculate the target angle based on the phase difference between the two measurement stations.

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