Improved multi-order extended cancellation batch processing method for GNSS external source signal

Abstract

The GNSS external source signal improved multi-order spread phase cancellation batch processing moving clutter suppression method is: first, read the received reference signal and echo signal; then, according to the preset theoretical maximum detection distance and Doppler shift threshold of the detection scene, set the segment number and cancellation order in the ECA algorithm for clutter suppression processing, and obtain signal peak value data; finally, judge whether the Doppler shift exceeds the preset Doppler threshold, reconstruct the moving clutter signal, and update the echo signal. The improved method can realize the moving clutter suppression within the Doppler threshold range by the detection-reconstruction cascade cancellation method under the condition of occupying lower computing resources.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of GNSS satellite signals, specifically to a GNSS external radiation source signal improved multi-order extended cancellation batch processing clutter suppression method. BACKGROUND

[0002] In addition to the detected target echo, the signal received by the echo antenna is mixed with many other signals, such as satellite direct waves, various noises and ground reflection clutter. Moreover, the power of the target signal is much smaller than that of these clutters, so the echo signal needs to be processed to extract the target echo containing target information from numerous signals. Currently, there are three commonly used methods for clutter suppression of echo signals in external radiation source radars: frequency domain filtering, spatial domain filtering and time domain filtering. Frequency domain filtering is to filter out unnecessary frequency components in the frequency domain to suppress clutter. Spatial domain filtering is usually used on array antennas to reduce the side lobes of the monitoring antenna and suppress clutter. Time domain filtering treats multi-path clutter as time-delayed signals of the reference signal, and adjusts the filter weights by certain criteria to filter out these time-delayed components. In engineering practice, the time domain filtering method shows good clutter suppression effect, so it has been widely used.

[0003] In target detection, most of the time, the interference is static multi-path clutter, but there are also phenomena of dynamic clutter interference caused by non-interested targets such as pedestrians or various scatterers such as wind-blown leaves. When there is dynamic clutter in the echo signal, the dynamic clutter will shield the weak target and affect the detection of the weak target. In addition, the ECA-B algorithm uses the reference signal and its time-delayed signal to construct the clutter subspace. Since the clutter time delay is unknown, it needs to traverse multiple time delay units to estimate the clutter parameters. The open-loop ECA-B algorithm involving matrix inversion operation has a larger computational load as the cancellation order increases. Therefore, it is necessary to improve the ECA-B algorithm.

[0004] Compared with the prior art:

[0005] Comparison with the technology of patent CN115113208A "Continuous wave radar clutter cancellation method based on clutter feature accurate recognition":

[0006] Patent CN115113208A is to solve the problem of clutter suppression of continuous wave radar in complex terrain such as cities or suburbs, and complex weather detection environment such as clouds and rain, while our method aims to provide a low-altitude target detection technology algorithm based on satellite radiation source signals.

[0007] The patent CN115113208A is a technical improvement based on adaptive moving target display technology, which effectively eliminates the interference of extended static clutter or dynamic clutter such as cloud and rain, while we improve the technology based on the extended cancellation algorithm to eliminate the interference of dynamic clutter.

[0008] The patent CN115113208A is a clutter cancellation method for target echo signals in continuous wave radar to eliminate static clutter and dynamic clutter, while we solve the problem of shielding weak targets when dynamic clutter and weak targets exist simultaneously based on the time-domain adaptive filtering algorithm to solve the interference of static clutter.

[0009] Comparison with the technology of patent CN109143231A "Digital television passive bistatic radar target detection method based on cyclic cancellation":

[0010] The patent CN109143231A reconstructs strong clutter echo signals using a target detection algorithm, and realizes the suppression of moving clutter through a time delay Doppler sliding resistor, while we obtain the target echo signal after clutter cancellation through the extended cancellation algorithm, and realize the filtering of dynamic clutter through improved clutter suppression processing.

[0011] The patent CN109143231A mainly processes a large number of sheet-shaped moving clutter such as cloud and rain clutter and ocean current clutter scanned by radar, while we mainly process static multipath clutter, which also includes dynamic clutter caused by pedestrians and other targets.

[0012] The patent CN109143231A does not consider the processing speed when suppressing clutter, while the improved algorithm realizes the suppression of dynamic clutter within the Doppler threshold range by using the cascade cancellation method of detection-reconstruction, which occupies lower computing resources and reduces the processing time and computational complexity to a certain extent. SUMMARY

[0013] To solve the above problems, the GNSS external radiation source signal improved multi-order extended cancellation batch processing dynamic clutter suppression method is provided, which improves the ECA-B algorithm. Since the multipath clutter is sparsely distributed in a small number of distance units, the strong clutter delay is estimated in advance, the cancellation order is reduced, and the computational complexity is reduced. Through the cascade cancellation method of detection-reconstruction, the dynamic clutter suppression within the Doppler threshold range is realized under the condition of occupying lower computing resources.

[0014] To achieve the above purpose, the technical scheme adopted by the present application is:

[0015] The GNSS external radiation source signal improved multi-order extended cancellation batch processing dynamic clutter suppression method comprises the following steps:

[0016] (1) Read the reference signal S ref(t) and echo signal S echo (t);

[0017] (2) According to the preset theory farthest detection distance R of the detection scene max and Doppler shift threshold value;

[0018] (3) Set the segment number B and cancellation order K in the ECA-B algorithm;

[0019] (4) Perform ECA-B clutter suppression processing according to the set segment number and cancellation order;

[0020] (5) Perform range-Doppler processing on the echo data after clutter suppression and the reference signal to obtain the time delay τ, Doppler shift f and amplitude A' corresponding to the signal peak value detected at this time; d

[0021] (6) Judge whether the Doppler shift exceeds the preset Doppler threshold value, if it exceeds the threshold value, it is indicated that the peak value detected is a weak target signal, if it does not exceed the threshold value, it is indicated that the peak value detected at this time is a moving clutter signal, and the moving clutter signal S' is reconstructed ref ;

[0022] (7) Reconstruct the moving clutter signal and update the echo signal.

[0023] As a further improvement of the application, step (2) specifically comprises:

[0024] (2.1) The theory farthest detection distance can be preliminarily estimated by combining the detection scene and the farthest detection distance formula

[0025] .

[0026] (2.2) Generally, the Doppler shift of the moving clutter is smaller than that of the moving target, so it can be considered that the signal smaller than a certain Doppler shift threshold value is a moving clutter, thereby subsequent operations are performed. The Doppler shift can be initialized by combining the detection scene and .

[0027] As a further improvement of the application, step (3) specifically comprises:

[0028] (3.1) The segment number B can be appropriately selected according to the data length of processing, and the cancellation order K can be set according to the farthest detection distance: τ max represents the time delay of the receiver at R max , and c is the propagation speed of electromagnetic wave.

[0029] (3.2) Convert the time delay τ max into the number of points in a sampling period, that is, the theory maximum cancellation order of ECA-B has:​

[0030] In this algorithm, the cancellation order K = K max / 3, and since the cancellation order is generally an integer, we round up K.

[0031] As a further improvement of the present invention, step (7) specifically includes:

[0032] (4.1) The reconstructed dynamic clutter signal can be expressed as: The result S after the last ECA-B processing eca-b As a new echo signal, namely S′ echo (t)=S eca-b (f), then return to step (4).

[0033] (4.2) After processing by the ECA-B algorithm in step 4, the moving clutter signal can be filtered out, and the detection of weak targets under moving clutter masking can be realized.

[0034] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0035] This invention proposes an improved multi-order extended phase cancellation batch processing method for suppressing dynamic clutter in GNSS external radiation source signals. The method first reads the received reference signal and echo signal; then, based on the preset theoretical maximum detection distance and Doppler frequency shift threshold for the detection scenario, it sets the number of segments and cancellation order in the ECA algorithm to perform clutter suppression processing and obtain the signal peak data; finally, it determines whether the Doppler frequency shift exceeds the preset Doppler threshold, reconstructs the dynamic clutter signal, and updates the echo signal. This improved method can achieve dynamic clutter suppression within the Doppler threshold range with lower computational resources through a detection-reconstruction cascaded phase cancellation method. Attached Figure Description

[0036] Figure 1 This is a flowchart of one embodiment of the present invention. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0038] Figure 1 This is a flowchart of one embodiment of the present invention. Detailed Implementation

[0040] like Figure 1 As shown, the dynamic clutter suppression method based on improved multi-order extended phase cancellation batch processing described in this invention includes:

[0041] (1) Read the reference signal S ref (t) and echo signal S echo(t);

[0042] (2) Based on the preset theoretical maximum detection distance R of the detection scenario max And Doppler frequency shift threshold.

[0043] (2.1) The theoretical maximum detection distance can be determined by combining the detection scenario and the formula for calculating the maximum detection distance.

[0044] Make a preliminary estimate.

[0045] (2.2) Generally, the Doppler frequency shift of moving clutter is relatively small compared to the moving target being detected. Therefore, signals with a Doppler frequency shift less than a certain threshold can be considered moving clutter for subsequent operations. Perform parameter initialization.

[0046] (3) Set the number of segments B and the cancellation order K in the ECA-B algorithm.

[0047] (3.1) The number of segments B can be appropriately selected based on the length of the data being processed, while the cancellation order K can be set based on the farthest detection distance: τ max R represents max The value at the corresponding receiver delay is denoted as c, where c is the propagation speed of electromagnetic waves.

[0048] (3.2) Delay τ max The number of points within a sampling period, i.e., the theoretical maximum cancellation order of ECA-B, is:

[0049] In this algorithm, the cancellation order K = K max / 3, and since the cancellation order is generally an integer, we round up K.

[0050] (4) Perform ECA-B clutter suppression processing according to the set number of segments and cancellation order.

[0051] (5) Perform range-Doppler processing on the echo data and reference signal after clutter suppression to obtain the time delay τ and Doppler frequency shift f corresponding to the peak signal detected at this time. d And amplitude A′.

[0052] (6) Determine whether the Doppler frequency shift exceeds the preset Doppler threshold. If it exceeds the threshold, it means that the detected peak is a weak target signal; if it does not exceed the threshold, it means that the detected peak is a clutter signal, and reconstruct the clutter signal S′. ref .

[0053] (7) Reconstruct the dynamic clutter signal and update the echo signal.

[0054] (7.1) The reconstructed dynamic clutter signal can be expressed as: The result S after the last ECA-B processing eca-b As a new echo signal, namely S′ echo (t)=S eca-b (t), and then return to step (4).

[0055] (7.2) After processing by the ECA-B algorithm in step 4, the moving clutter signal can be filtered out, and the detection of weak targets under moving clutter masking can be realized.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. An improved multi-order extended phase-deletion batch processing method for suppressing dynamic clutter in GNSS external radiation source signals, comprising the following steps, characterized in that: (1) Read the reference signal and echo signal ; (2) Based on the preset theoretical maximum detection distance of the detection scenario and Doppler frequency shift threshold; (3) Set the number of segments B and the cancellation order K in the ECA-B algorithm; (4) Perform ECA-B clutter suppression processing according to the set number of segments and cancellation order; (5) Perform range-Doppler processing on the echo data and reference signal after clutter suppression to obtain the time delay τ and Doppler frequency shift corresponding to the peak signal detected at this time. and amplitude ; (6) Determine whether the Doppler frequency shift exceeds the preset Doppler threshold. If it exceeds the threshold, it means that the detected peak is a weak target signal; if it does not exceed the threshold, it means that the detected peak is a dynamic clutter signal. Reconstruct the dynamic clutter signal. ; (7) Reconstruct the dynamic clutter signal and update the echo signal; Step (7) specifically includes: (7.1) The reconstructed dynamic clutter signal is represented as: and the results after the last ECA-B processing As a new echo signal, i.e. Then return to step (4); (7.2) After processing by the ECA-B algorithm in step 4, the dynamic clutter signal in the new echo signal can be filtered out, realizing the detection of weak targets under dynamic clutter masking.

2. The improved multi-order extended phase cancellation batch processing method for suppressing dynamic clutter in GNSS external radiation source signals according to claim 1, characterized in that: Step (2) specifically includes: (2.1) The theoretical maximum detection distance is calculated by combining the detection scenario and the formula for finding the maximum detection distance. Make a preliminary estimate; (2.2) Doppler frequency shift is achieved by combining the detection scenario and Perform parameter initialization.

3. The improved multi-order extended phase cancellation batch processing method for suppressing dynamic clutter in GNSS external radiation source signals according to claim 1, characterized in that, Step (3) specifically includes: (3.1) The number of segments B can be appropriately selected based on the length of the data being processed, while the cancellation order K is set based on the farthest detection distance: , express The corresponding receiver delay is at that location. The speed at which electromagnetic waves propagate; (3.2) Delay The number of points within a sampling period, i.e., the theoretical maximum cancellation order of ECA-B, is: Take the cancellation order Round up K.

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