A radar emitter passive positioning method based on multi-channel joint accumulation

Abstract

This invention discloses a passive localization method for radar radiation sources based on multi-channel joint accumulation, applied in the field of radar technology. It addresses the problem that direct localization algorithms based on maximizing the objective function value suffer performance degradation when the received signal-to-noise ratio (SNR) is low. This invention utilizes fractional Fourier transform to accumulate energy in the received signal, aligns the envelopes of each receiving channel based on the time delay characteristics of the fractional Fourier transform, thereby achieving signal energy accumulation across multiple channels. Finally, it locates the radiation source target through a two-dimensional position parameter search. This method effectively fuses signals from multiple receivers, achieving accurate localization of linear frequency modulated (LFM) signal radiation sources even under low SNR conditions.

Description

Technical Field

[0001] This invention belongs to the field of radar technology, and specifically relates to a passive positioning technology for external radiation sources of linear frequency modulated signals under low signal-to-noise ratio conditions. Background Technology

[0002] With the increasing complexity of the electromagnetic environment, the requirements for the concealment of detection equipment are becoming more and more stringent. To meet this demand, passive detection systems that utilize the target's own radiation signals for localization have been widely used. Linear frequency modulated (LFM) signals, due to their large time-bandwidth product and insensitivity to Doppler frequency shift, are widely used in various radiation sources. Therefore, locating LFM signal radiation sources is of great significance.

[0003] However, with the rise of low probability of intercept (LPI) technology, the signals emitted by radiation sources are becoming increasingly directional and the transmission beams are becoming narrower. As a result, receivers often receive signals from the sidelobes of the transmission beam, leading to a low signal-to-noise ratio in the received signal.

[0004] Currently, passive localization methods for radiation sources mainly fall into two categories: a two-step localization method based on cross-correlation-time difference of arrival (TDOA) and a direct position determination (DPD) algorithm based on maximizing the objective function value. Specifically, TDOA first performs cross-correlation processing on the received signals from each receiver to obtain the time difference of arrival between receivers, and then uses the least squares method to solve the hyperbolic / surface equations to achieve target localization. However, this method has large errors and requires sophisticated receiver placement. DPD fuses the signals from each receiving channel and achieves localization through a two-dimensional position grid search method. However, the localization performance of this method degrades when the signal-to-noise ratio (SNR) of the received signal decreases. Therefore, there is an urgent need to study passive localization methods for external radiation sources with linear frequency modulated (LFM) signals under low SNR conditions. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a passive radar radiation source localization method based on multi-channel joint accumulation, which can effectively fuse signals from multiple receivers and achieve accurate localization of linear frequency modulated signal radiation sources under low signal-to-noise ratio conditions.

[0006] The technical solution adopted in this invention is: a passive localization method for radar radiation sources based on multi-channel joint accumulation. The application scenario includes: an external radiation source and multiple receivers; the external radiation source emits a linear frequency modulated pulse signal, and the receivers are used to receive the direct wave signal; the process of locating the external radiation source includes the following steps:

[0007] S1. Perform a fractional Fourier transform on the direct wave signal received by each receiver to obtain the fractional Fourier transform plane, and select any receiver as the reference receiver.

[0008] S2. Grid the detection area, select the search position (x,y), and calculate the time delay difference between the radiation source's transmitted signal at that position and the signal transmitted to each receiver and the reference receiver.

[0009] S3. Based on the time delay characteristics and time delay difference of the fractional Fourier transform, the envelopes of each receiver are aligned in the fractional Fourier transform plane, thereby realizing non-coherent accumulation between receiver channels and outputting the accumulation peak as the target function value at position (x,y).

[0010] S4. Traverse each grid location within the detection area, repeating steps S2-S3, and finally select the location (x) corresponding to the maximum objective function value. o ,y o (This is used as the location result.)

[0011] The beneficial effects of this invention are as follows: This invention provides a passive localization method for linear frequency modulated (LFM) signal radiation sources based on multi-channel joint accumulation, belonging to the field of radar technology. This invention addresses the passive localization problem of radiation sources transmitting LFM pulse signals. It utilizes fractional Fourier transform to accumulate energy in the received signal, aligns the envelopes of each receiving channel based on the time delay characteristics of the fractional Fourier transform, thereby achieving signal energy accumulation across multiple channels. Finally, it locates the radiation source target through a two-dimensional position parameter search. The process included in this invention can be implemented using a fast discrete algorithm based on fractional Fourier transform, which is beneficial for engineering implementation. Attached Figure Description

[0012] Figure 1 This is a flowchart of an embodiment of the present invention.

[0013] Figure 2 These are the received signals of each receiver in the embodiments of the present invention.

[0014] Figure 3 This is a diagram showing the positioning results of the method proposed in this embodiment of the invention.

[0015] Figure 4 The image shows the location results for TDOA.

[0016] Figure 5 This is a diagram showing the DPD localization results. Detailed Implementation

[0017] This invention primarily utilizes the scientific computing software Matlab R2021a for simulation experiments to verify its correctness. The embodiments of this invention are further described below with reference to the accompanying drawings.

[0018] Please see Figure 1 The present invention proposes a passive localization method for linear frequency modulated signal radiation sources based on multi-channel joint accumulation, which is implemented through the following steps:

[0019] Step 1: The external radiation source emits a linear frequency modulated pulse signal and then receives the direct wave signal from the radar.

[0020] In this embodiment, the external radiation source emits a linear frequency modulated signal s tran (t):

[0021]

[0022] Where t represents the time variable, T p Let f be the pulse width, f0 be the center frequency, k be the frequency modulation slope, and A be the pulse signal amplitude. The signal received by the i-th receiver is s. ri (t):

[0023] s ri (t)=A i s tran (t-τ i )

[0024] Where, τ i A represents the time delay from the emitted linear frequency modulated signal to the i-th receiver. i Let be the amplitude of the signal received by the i-th receiver, and let M be the number of receivers. The time delay depends on the distance between the receiver and the radiation source.

[0025]

[0026] Where ||·|| denotes the calculation of the L2 norm of the internal vector, P t =(x t ,y t ) represents the location of the radiation source, x t ,y t P represents the x and y coordinates of the location of the radiation source. i =(x i ,y i Let x be the position of the i-th receiver. i ,y i Let x and y represent the x and y coordinates of the location of the i-th receiver, and c represent the speed of light.

[0027] In this embodiment, the system parameters used are as follows: the radiation source target is located at (12, 60) km in a two-dimensional Cartesian coordinate system; the radiation source emits a linear frequency modulated signal with a center frequency of 210 MHz, a signal bandwidth of 3 MHz, and a pulse width of 100 μs; there are a total of 4 receivers located at (-50, 20) km, (-10, 0) km, (10, 0) km, and (50, 20) km, respectively; the digital down-conversion reference frequency of the receivers is 200 MHz; the sampling frequency of the receivers is 60 MHz; and the signal-to-noise ratio of the direct wave signal received by the receivers is -8 dB.

[0028] Step 2: Perform a fractional Fourier transform on the direct wave signal received by each receiver to obtain the fractional Fourier transform plane, and select any receiver as the reference receiver.

[0029] In this embodiment, the direct wave signal s received by each receiver ri (t) Perform a fractional Fourier transform to obtain the fractional Fourier transform plane:

[0030]

[0031] in:

[0032]

[0033] Among them, A α Let α represent the integral kernel amplitude, α represent the transform order, δ(ut) be the impulse function, n represent an integer, and u represent the coordinates in the fractional Fourier transform domain.

[0034] The first receiver (located at (-50, 20) km) is chosen as the reference receiver, and its received signal, after undergoing a fractional Fourier transform, is denoted as f. ref (α,u).

[0035] Step 3: Grid the detection area, select the search position (x, y), and calculate the time delay difference between the radiation source's transmitted signal at that position and the signal transmitted to each receiver and the reference receiver.

[0036] The detection area is gridded, and a search position (x, y) is selected. The time delay difference between the emitted signal from the radiation source at that position and the signal to each receiver and the reference receiver is calculated.

[0037] τ i-ref =τ i -τ ref

[0038] Where, τ ref =τ1 is the time delay from the emission signal from the radiation source to the reference receiver.

[0039] Step 4: Based on the time delay characteristics and time delay difference of the fractional Fourier transform, the envelopes of each receiver are aligned in the fractional Fourier transform plane to achieve non-coherent accumulation between receiver channels, and the accumulated peak value is output as the target function value at position (x,y).

[0040] In this embodiment, step 4 includes the following process:

[0041] First, for the search position (x, y), the envelopes of each receiver are aligned in the fractional Fourier transform plane based on the time delay characteristics and time delay difference of the fractional Fourier transform:

[0042]

[0043] Then, the fractional Fourier transform results of the signals from each receiver after envelope alignment are noncoherently accumulated, and the maximum value of the accumulation is output as the objective function value at position (x,y):

[0044]

[0045] The accumulated peak value is output as the objective function value at position (x,y).

[0046] Step 5: Traverse each grid location within the detection area, repeating steps 3-4, and find the location (x) corresponding to the maximum objective function value. o ,y o This is the location result.

[0047] In this embodiment, steps 3 to 4 are repeated for each grid location within the detection area to obtain the objective function value l(x,y) for each grid location, and the location (x,y) corresponding to the peak value of the objective function value. o ,y o This is the location result of the LFM pulse signal radiation source.

[0048] To demonstrate the effectiveness of this method, Figure 4 and Figure 5 The passive localization results of the traditional TDOA and DPD algorithms are shown. Due to the low signal-to-noise ratio of the received signal, the localization accuracy of existing methods is far lower than that of the method obtained in this invention.

[0049] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of the claims of the invention.

Claims

1. A passive localization method for radar radiation sources based on multi-channel joint accumulation, characterized in that, Application scenarios include: an external radiation source and multiple receivers; the external radiation source emits linear frequency modulated pulse signals, and the receivers are used to receive direct wave signals; the process of locating the external radiation source includes the following steps: S1. Perform a fractional Fourier transform on the direct wave signal received by each receiver to obtain the fractional Fourier transform plane, and select any receiver as the reference receiver. S2. Grid the detection area and select the search location. Calculate position The time delay difference between the signal emitted by the radiation source to each receiver and to the reference receiver; S3. Based on the time delay characteristics and time delay difference of the fractional Fourier transform, the envelopes of each receiver are aligned in the fractional Fourier transform plane, thereby achieving non-coherent accumulation between receiver channels, and the accumulated peak value is output as the position. The objective function value at that point; S4. Traverse each grid location within the detection area, repeating steps S2-S3, and finally select the location corresponding to the maximum objective function value. As a location result.

2. The passive localization method for radar radiation sources based on multi-channel joint accumulation according to claim 1, characterized in that, The fractional Fourier transform plane representation of the i-th receiver is: ； in, For the i-th receiver to receive the signal, t represents the time variable, A α Let α represent the integral kernel amplitude, α represent the transform order, δ(ut) be the impulse function, n represent an integer, and u represent the coordinates in the fractional Fourier transform domain.

3. The passive localization method for radar radiation sources based on multi-channel joint accumulation according to claim 2, characterized in that, Step S2 specifically involves: Let the time delay from the linear frequency modulated signal emitted by the radiation source to the i-th receiver be denoted as . The time delay from the linear frequency modulated signal emitted by the radiation source to the reference receiver is... Then the time delay difference is .

4. The passive localization method for radar radiation sources based on multi-channel joint accumulation according to claim 3, characterized in that, The fractional Fourier transform result of the signal from the i-th receiver after envelope alignment is expressed as: 。 5. The passive localization method for radar radiation sources based on multi-channel joint accumulation according to claim 4, characterized in that, Location The objective function value at point is expressed as: M represents the number of receivers.

Images