CN109521418A - Ground-based radar angle-measuring method based on interference field - Google Patents

Abstract

A ground-based radar angle measurement method based on interference field mainly solves the problem of improving the azimuth angle measurement accuracy of the target to be estimated under far-field and narrow-band conditions. The steps that the present invention realizes are as follows: (1) construct the angle measurement model of two ground-based radars; (2) design the transmission signal of ground-based radar A and ground-based radar B; (3) by arranging two kinds of transmission signals of different initial phases, obtain Two kinds of interference waves at the target; (4) by taking modulus processing on the sum and difference channels of the two kinds of interference wave signals in the ground-based radar A respectively, and obtaining the sum signal and the difference signal; (5) using the obtained difference and ratio Check the table to get the aurament of the target. The invention can measure the accurate azimuth angle information of the target to be estimated by using the periodically changing angle discrimination curve through the method of measuring the angle of the ground-based radar based on interference, thereby significantly improving the angle-measuring precision of the target to be estimated by the ground-based radar.

Description

Angle measurement method of ground-based radar based on interference field

technical field

The invention belongs to the technical field of radar, and further relates to a radar angle measurement method based on interference in the technical field of radar angle measurement. The invention can be used to measure the azimuth angle of the long-distance static point target to be estimated under the condition of narrow band.

Background technique

The main task of radar angle measurement is to detect the spatial position of the target. With the deepening understanding of the field of radar angle measurement, the tracking of target angle has been widely used and developed in this field, and there are already a large number of angle estimation algorithms to realize the angle estimation of the target. However, due to the continuous deepening of the application of radar systems, the actual tracking requirements have higher and higher detection capabilities for target angles. From conventional sliding window angle measurement technology to amplitude single pulse angle measurement technology, even phase single pulse angle measurement technology, although sliding window angle measurement technology, amplitude single pulse angle measurement technology and phase single pulse angle measurement technology The angle measurement accuracy has been improved, but the degree of improvement in angle measurement accuracy is not high.

Sichuan Jiuzhou Air Traffic Control Technology Co., Ltd. disclosed a single-pulse high-precision angle measurement system and its method in its patent application (patent application number 201410053339.8, publication number CN103792532A). angle measurement method. The concrete steps that this method realizes are, (1) utilize the synchronous PN code to demodulate the baseband digital signal, restore the original useful signal, noise, interference signal are suppressed; Amplitude detection; (3) use the amplitude of the sum and difference channels to perform phase judgment, and calculate the sum and difference amplitude information and phase judgment results; (4) obtain the OBA value function according to the calculated sum and difference amplitude information and phase judgment results and Perform target bearing calculations. The disadvantage of this method is that in the process of using synchronous pseudo-random codes to demodulate the baseband digital signal and restore the original signal from the noise and interference signal, the existing technology cannot make the useful signal and the interference signal and noise completely Separation, that is, useful signals may be mixed with noise and interference signals, resulting in errors in the subsequent single-pulse angle measurement results, making the angle measurement accuracy not high.

Xidian University disclosed a kind of machine-scanned meter-wave radar in the patent document "Angle measurement method of machine-scanned meter-wave radar in the case of multiple targets" (patent application number CN201410018152.4, publication number CN103744077A). Angle measurement method in the target case. The concrete steps that this method realizes are: (1) the antenna is divided into two sub-arrays, and each sub-array is connected with a receiver to form left and right two-way channels; pulse signal; (3) perform clutter target cancellation processing on the received echo signal data; (4) coherently accumulate the two-way data after clutter cancellation; (5) obtain the sum beam from the accumulated two-way data and the difference beam; (6) Use the traditional monopulse method to measure the off-axis angle of the desired target, and add the off-axis angle to the reference angle to obtain the exact angle of the desired target; (7) Repeat steps (3)-(6 ) to obtain the accurate angles of all targets in turn. The disadvantage of this method is that when the clutter target cancellation processing is performed on the echo data received by the left and right channels formed by the two antenna sub-arrays, the echo and clutter cannot be canceled well, resulting in The cancellation results will affect the coherent accumulation, and then affect the accuracy of the measured off-axis angle of the desired target, and the accuracy of the final angle measurement results is still insufficient.

SUMMARY OF THE INVENTION

The object of the present invention is to address the deficiencies of the above-mentioned prior art, and propose a ground-based radar angle measurement method based on interference field, so as to realize high-precision measurement of the azimuth angle of the static point target to be estimated.

The train of thought of realizing the object of the present invention is to construct the angle-measuring models of two ground-based radars; design the transmission signals of ground-based radar A and ground-based radar B, so that the single carrier frequency signals emitted by the two ground-based radars arrive at the stationary point target to be estimated simultaneously; change The initial phase of the transmitted signals of the two ground-based radars generates two kinds of interference field signals at the equidistant ring; the two kinds of interference field signals are received by the ground-based radar A, and the two echo signals are in the sum channel and difference channel of the ground-based radar A Perform processing to generate a sum signal and a difference signal; use the difference and ratio look-up table to obtain the azimuth angle of the static point target to be estimated.

Concrete steps of the present invention are as follows:

(1) Construct the angle measurement model of two ground-based radars:

(1a) With the ground-based radar A as the coordinate origin, the due east direction of the ground-based radar A is the X-axis, and the due north direction of the ground-based radar A is the Y-axis, and a rectangular coordinate system is established;

(1b) Set the ground-based radar B at the distance L from the ground-based radar A on the X axis, and obtain the angle measurement models of the two ground-based radars, 60m≤L≤100m;

(2) Ground-based radar A and ground-based radar B transmit single carrier frequency signals:

(2a) Using the cosine formula, calculate the distance difference between ground-based radar A and ground-based radar B and the stationary point target to be estimated;

(2b) Divide the distance difference by the propagation speed of electromagnetic waves in vacuum to obtain the time delay Δτ of the transmitted signals of the two ground-based radars;

(2c) Ground-based radar A transmits a single-carrier frequency signal, and ground-based radar B transmits a single-carrier frequency signal of the same frequency after the transmission time delay Δτ of ground-based radar A;

(3) Generate two kinds of interference field signals:

(3a) The initial phases of ground-based radar A and ground-based radar B are both set to 0, and the electromagnetic waves emitted by the two ground-based radars are interfered in an equidistant ring to obtain the first type of interference field signal;

(3b) Set the initial phase of ground-based radar A to 0, and the initial phase of ground-based radar B to π, and interfere the electromagnetic waves emitted by the two ground-based radars in an equidistant ring to obtain the second interference field signal;

(4) Generate sum signal and difference signal:

(4a) The ground-based radar A receives the echoes of two kinds of interference field signals, and obtains two kinds of echo signals;

(4b) The first echo signal and the second echo signal are modulo-added in the sum channel of the ground-based radar A to obtain the sum signal;

(4c) taking the modulo subtraction of the first echo signal and the second echo signal in the difference channel of the ground-based radar A to obtain the difference signal;

(5) Obtain the azimuth angle of the static point target to be estimated:

(5a) dividing the difference signal by the sum signal to obtain the difference and ratio;

(5b) Look up the azimuth angle of the static point target to be estimated relative to the ground-based radar A corresponding to the difference and the ratio from the angle discrimination curve table.

Compared with the prior art, the present invention has the following advantages:

First, because the present invention uses the superposition of electromagnetic waves emitted by two ground-based radars to obtain two kinds of interference waves, and uses periodically changing interference waves to accurately characterize the azimuth information of the static point target to be estimated, which overcomes the ground-based radar echo in the prior art The problem of inaccurate description of the space azimuth angle information of the static point target to be estimated caused by the single wave signal waveform change enables the present invention to estimate the azimuth angle of the static point target more accurately.

The second, because the present invention has carried out modulo-taking operation to two kinds of echo signals in the sum difference channel of ground-based radar A, first two kinds of echo signals are taken modulo-adding in the sum channel of ground-based radar A to obtain the sum signal, and then The two echo signals are modulo-subtracted in the difference channel of the ground-based radar A to obtain the difference signal, which overcomes the inability of echo and clutter cancellation in the prior art when the static point target to be estimated is in a complex environment of noise and interference. Thoroughly, it leads to the problem that the correct sum signal and difference signal cannot be obtained, so that the present invention can accurately obtain the sum signal and difference signal of the static point target to be estimated, and enhance the accuracy and reliability of the static point target azimuth estimation.

Description of drawings

Fig. 1 is a flowchart of the present invention;

Fig. 2 is the schematic diagram of the ground-based radar angle measurement model established by the present invention;

Fig. 3 is the angle discrimination curve that traditional monopulse angle measurement method obtains;

Fig. 4 is a simulation result diagram of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

In conjunction with accompanying drawing 1, the specific steps of the present invention are further described.

Step 1. Construct angle measurement models of two ground-based radars.

With the ground-based radar A as the coordinate origin, the due east direction of the ground-based radar A is the X-axis, and the due north direction of the ground-based radar A is the Y-axis, and a rectangular coordinate system is established.

Set ground-based radar B at a distance L from ground-based radar A on the X-axis, and obtain the angle measurement models of the two ground-based radars, as shown in Figure 2, A and B represent the positions of the two ground-based radars on the X-axis, L Indicates the baseline length between ground-based radar A and ground-based radar B, θ indicates the angle range of the observed azimuth dimension, θ ₀ indicates the azimuth angle of the stationary point target to be estimated relative to ground-based radar A, and R ₀ indicates the distance between the stationary point target to be estimated and the ground-based radar. The distance of radar A, P ₀ represents the position of the static point target to be estimated, P ₁ represents the position corresponding to the maximum deflection angle of the 3dB beam width of the signal transmitted by ground-based radar A relative to the center, and the two gray fan-shaped areas are two ground-based The coverage of the 3dB beam of the radar transmission signal, the transparent ring indicates the equidistant ring where the static point target to be estimated is located, 60m≤L≤100m.

Among them, ground-based radar A both transmits and receives single-carrier frequency signals, and ground-based radar B only transmits single-carrier frequency signals.

Step 2, ground-based radar A and ground-based radar B transmit single carrier frequency signals.

Using the cosine formula, calculate the distance difference between ground-based radar A and ground-based radar B and the static point target to be estimated.

The described cosine formula is as follows:

Among them, ΔR represents the difference between the distance between ground-based radar A and the static point target to be estimated and the distance between ground-based radar B and the static point target to be estimated, _R0 represents the distance between ground-based radar A and the static point target to be estimated, represents the square root operation, L represents the distance between ground-based radar A and ground-based radar B, cos represents the cosine function, θ ₀ represents the azimuth angle of the static point target to be estimated relative to ground-based radar A, and c represents the propagation velocity of electromagnetic waves in vacuum.

Divide the distance difference by the propagation speed of electromagnetic waves in vacuum to obtain the time delay Δτ of the two ground-based radars' transmitted signals.

In order to make the single-carrier frequency signals transmitted by the two ground-based radars form a stable interference effect at the equidistant ring where the stationary point target is located, it is necessary to make the single-carrier frequency signals transmitted by the two ground-based radars reach the location of the static point target to be estimated at the same time equidistant area. Ground-based radar A transmits a single carrier frequency signal, and ground-based radar B transmits a single carrier frequency signal of the same frequency after ground-based radar A transmits a time delay Δτ.

The signal transmitted by ground-based radar A is:

The signal transmitted by the ground-based radar B is:

Among them, T _p represents the pulse repetition period, f _c represents the carrier frequency of the transmitted signal, φ ₁ and φ ₂ represent the initial phases of the transmitted signals of ground-based radar A and ground-based radar B, respectively.

Step 3, generating two kinds of interference field signals.

The initial phases of ground-based radar A and ground-based radar B are both set to 0, and the electromagnetic waves emitted by the two ground-based radars are interfered in an equidistant ring to obtain the first interference field signal.

The initial phase of ground-based radar A is set to 0, the initial phase of ground-based radar B is set to π, and the electromagnetic waves emitted by the two ground-based radars are interfered in an equidistant ring to obtain the second interference field signal.

The time delay difference between the transmitted signals of two ground-based radars arriving at any point on the equidistant ring is:

Among them, Δτ(θ) represents the time delay of the two ground-based radars transmitting signals at any point on the equidistant ring, and Δτ(θ ₀ ) represents the time delay of the two ground-based radars transmitting signals at the static point target to be estimated.

In the target area (θ-θ ₀ )≤θ _3dB , the maximum value of the arrival time difference of the transmitted signals of the two ground-based radars is:

Since the 3dB beamwidth of the radar antenna is usually small under narrow-band conditions, it can be approximated that the transmission signals of ground-based radar A and ground-based radar B can reach any point on the equidistant ring at the same time, so the transmission signals of ground-based radar A and ground-based radar B can be at A stable interference effect is formed in the target area of the stationary point to be estimated.

The interference field signal in the equidistant ring can be expressed as:

Set the initial phase of ground-based radar A to 0, and the initial phase of ground-based radar B to π, the obtained first interference wave can be expressed as:

Set the initial phase of ground-based radar A to 0, and the initial phase of ground-based radar B to π, the obtained first interference wave can be expressed as:

Step 4, generating a sum signal and a difference signal.

The ground-based radar A receives the echoes of two kinds of interference field signals and obtains two kinds of echo signals.

The first type of echo signal and the second type of echo signal are modulo-added in the sum channel of the ground-based radar A to obtain the sum signal.

The first type of echo signal and the second type of echo signal are modulo subtracted in the difference channel of the ground-based radar A to obtain the difference signal.

The first echo signal received by ground-based radar A can be expressed as:

The second echo signal received by ground-based radar A can be expressed as:

The sum signal of the integrated channel of ground-based radar A can be expressed as:

The sum signal of the integrated channel of ground-based radar A can be expressed as:

Step 5, obtain the azimuth angle of the static point target to be estimated.

According to the following formula, the difference signal at the target to be estimated is divided by the sum signal to obtain the difference sum ratio:

in, Indicates the difference and ratio of the target to be estimated.

Divide the difference signal in the equidistant ring by the sum signal to obtain the following difference and ratio function as a function of azimuth:

Taking the angle range of the equidistant ring relative to the ground-based radar A as the abscissa, and the difference and ratio as the ordinate, the angle discrimination curve table of the angle range is drawn from the difference and ratio corresponding to the angle range, as shown in Figure 3.

Find the azimuth angle of the static point target to be estimated relative to the ground-based radar A corresponding to the difference and the ratio from the angle discrimination curve table in Fig. 3 .

The effects of the present invention will be further described below in combination with simulation experiments.

1. Simulation experimental conditions:

The hardware test platform of the simulation experiment of the present invention is: processor is CPU intel Core i5-6500, main frequency is 3.2GHz, internal memory 4GB; Software platform is: Windows 7 ultimate edition, 64 operating systems, MATLAB R2012b.

2. Simulation content Simulation result analysis:

There are two simulation experiments of the present invention, the first simulation is to use the monopulse angle measurement method of the prior art to simulate the azimuth measurement of the static point target to be estimated, and the second simulation is to use the angle measurement method of the present invention , to simulate the azimuth measurement of the stationary point target to be estimated.

Simulation 1, use the existing monopulse angle measurement technology to simulate the azimuth measurement of the stationary point target to be estimated, and obtain the angle detection curve shown in Figure 3. The angle detection curve is the angle of the stationary point target to be estimated relative to the ground-based radar The range is the abscissa, and the unit of the abscissa is radian, and the difference and ratio are the ordinate, and the unit of the ordinate is 1. Analysis of the simulation results shows that within the angle range of the stationary point target to be estimated relative to the ground-based radar, the angle detection curve obtained by the prior art only changes monotonously once, and the angle measurement accuracy is not high.

Simulation 2, using the angle measurement method of the present invention, simulates the azimuth measurement of the stationary point target to be estimated, and the simulation parameters used in the simulation experiment of the present invention are as shown in table 1:

Table 1 list of simulation parameters

carrier frequency 3GHz pulse repetition frequency 100KHz Radar A [0,0] Radar B [0,65] Target [R₀cosθ₀,R₀sinθ₀] Baseline length L 65m assumed target angle 30° Transmit signal bandwidth 8MHz

Use the simulation method of the present invention to obtain the angle detection curve as shown in Figure 4, the angle detection curve is based on the angle range of the equidistant ring relative to the ground-based radar A as the abscissa, the unit of the abscissa is the angle, and the difference and ratio is the ordinate .

Comparing the simulation results of Fig. 3 and Fig. 4, it can be seen that the angle detection curve of the simulation of the present invention changes periodically, and the period of change is restricted by the carrier frequency of the transmitted signal and the baseline length between the bistatic radars. By changing the carrier frequency of the signal transmitted by the ground-based radar and the baseline length between the ground-based radar, the size of the change period can be changed, thereby changing the measurement accuracy of the azimuth angle. Therefore, the accuracy of the interference-based ground-based radar angle measurement technology used in the present invention is far higher than the angle measurement accuracy of the existing single-pulse angle measurement method.

Claims (2)

1. a ground-based radar angle measurement method based on interference field, is characterized in that, generates two kinds of interference field signals, generates and signal and difference signal; The step of this method comprises as follows: (1) Construct the angle measurement model of two ground-based radars: (1a) With the ground-based radar A as the coordinate origin, the due east direction of the ground-based radar A is the X-axis, and the due north direction of the ground-based radar A is the Y-axis, and a rectangular coordinate system is established; (1b) Set the ground-based radar B at the distance L from the ground-based radar A on the X axis, and obtain the angle measurement models of the two ground-based radars, 60m≤L≤100m; (2) Ground-based radar A and ground-based radar B transmit single carrier frequency signals: (2a) Using the cosine formula, calculate the distance difference between ground-based radar A and ground-based radar B and the stationary point target to be estimated; (2b) Divide the distance difference by the propagation speed of electromagnetic waves in vacuum to obtain the time delay Δτ of the transmitted signals of the two ground-based radars; (2c) Ground-based radar A transmits a single-carrier frequency signal, and ground-based radar B transmits a single-carrier frequency signal of the same frequency after the transmission time delay Δτ of ground-based radar A; (3) Generate two kinds of interference field signals: (3a) The initial phases of ground-based radar A and ground-based radar B are both set to 0, and the electromagnetic waves emitted by the two ground-based radars are interfered in an equidistant ring to obtain the first type of interference field signal; (3b) Set the initial phase of ground-based radar A to 0, and the initial phase of ground-based radar B to π, and interfere the electromagnetic waves emitted by the two ground-based radars in an equidistant ring to obtain the second interference field signal; (4) Generate sum signal and difference signal: (4a) The ground-based radar A receives the echoes of two kinds of interference field signals, and obtains two kinds of echo signals; (4b) The first echo signal and the second echo signal are modulo-added in the sum channel of the ground-based radar A to obtain the sum signal; (4c) taking the modulo subtraction of the first echo signal and the second echo signal in the difference channel of the ground-based radar A to obtain the difference signal; (5) Obtain the azimuth of the static point target: (5a) dividing the difference signal by the sum signal to obtain the difference and ratio; (5b) Look up the azimuth angle of the static point target to be estimated relative to the ground-based radar A corresponding to the difference and the ratio from the angle discrimination curve table. 2. the ground-based radar angle measuring method based on interference field according to claim 1, is characterized in that, the cosine formula described in step (2a) is as follows: Among them, ΔR represents the difference between the distance between ground-based radar A and the static point target to be estimated and the distance between ground-based radar B and the static point target to be estimated, _R0 represents the distance between ground-based radar A and the static point target to be estimated, represents the square root operation, L represents the distance between ground-based radar A and ground-based radar B, cos represents the cosine function, θ ₀ represents the azimuth angle of the static point target to be estimated relative to ground-based radar A, and c represents the propagation velocity of electromagnetic waves in vacuum.