Space-based air defense radar signal doppler tolerance expansion method

Abstract

The application discloses a kind of space-based air defense detection radar signal Doppler tolerance extension methods, belong to the technical field of spaceborne microwave radar, including the following steps: S1: carrying out fast Fourier transform, the received radar echo signal is carried out fast Fourier transform;S2: constructing matched filter, matched filter is constructed according to transmitting signal, and compensation is carried out to matched function;S3: spectrum shift is carried out to matched filter, and the matched filter that is well constructed is translated, so that it is aligned with echo signal spectrum;S4: pulse compression, echo signal is multiplied by the matched filter after windowing, then Fourier transform is carried out, and pulse compression is completed.The application is processed by spectrum shift to echo signal, solves the problem that peak power drops after pulse compression, significantly improves the target detection performance of space-based radar in complex dynamic environment.

Description

Technical Field

[0001] This invention relates to the field of spaceborne microwave radar technology, and more specifically, to a method for extending the Doppler tolerance of space-based air detection radar signals. Background Technology

[0002] Space-based radar represents one of the pinnacles of modern radar technology, its core value lying in overcoming the inherent limitations of ground-based and air-based platforms. By deploying radar in outer space, the system can escape the constraints of the Earth's curvature, complex terrain, and atmospheric attenuation, achieving near real-time, all-weather, and all-time coverage of any region globally. This unique "high-altitude" perspective gives it an irreplaceable technological advantage in monitoring global areas, providing effective data support for scientific research.

[0003] To achieve long-range, high-precision detection of moving targets in the air, space-based radars generally employ hourly wideband signal systems. However, this signal system faces inherent technical bottlenecks in engineering practice. Due to the relatively narrow absolute bandwidth of the signal itself, the Doppler frequency offset generated by high-speed targets accounts for a significant proportion of the signal bandwidth, resulting in the inability to achieve effective coherent energy accumulation after pulse compression, causing main lobe broadening and peak power attenuation. This "Doppler mismatch" effect directly weakens the target detection signal-to-noise ratio, significantly shortens the radar's effective detection range, and fundamentally restricts the system's ability to detect and track key threats early and stably. Summary of the Invention

[0004] The purpose of this invention is to address the inherent defect in traditional processing methods for space-based air detection radar using hourly wide bandwidth signals, where Doppler frequency offset leads to a decrease in pulse compression power. This invention proposes a Doppler tolerance extension method for space-based air detection radar signals. Its core objective is to solve the problem of reduced peak pulse compression power for high-speed targets by accurately compensating for Doppler frequency offset in the frequency domain, thus providing key technical support for space-based radar to achieve early detection and stable tracking of moving targets.

[0005] To achieve the above objectives, the technical solution adopted in this invention is as follows: a Doppler tolerance extension method for space-based air detection radar signals. This method first constructs a frequency domain compensation function that precisely matches the target's Doppler frequency shift. By performing spectral shifting on the echo signal, it corrects the Doppler mismatch, ensuring optimal coherent energy accumulation after pulse compression, thereby effectively solving the peak power reduction problem caused by Doppler frequency offset. Specifically, it includes:

[0006] 10) Perform Fast Fourier Transform: Perform Fast Fourier Transform on the received radar echo signal.

[0007] 20) Construct a matched filter: Construct a matched filter based on the transmitted signal and compensate the matched function.

[0008] 30) Spectral shift of the matched filter: The constructed matched filter is shifted to align with the spectrum of the echo signal.

[0009] 40) Perform pulse compression: Multiply the echo signal with the windowed matched filter, and then perform Fourier transform to complete pulse compression.

[0010] As a preferred embodiment of the present invention, step S1 specifically includes:

[0011] For the received digital echo signal Perform a Fast Fourier Transform to obtain the spectrum of the echo signal. The calculation method is as follows:

[0012] ;

[0013] As a preferred embodiment of the present invention, step S2 specifically includes:

[0014] S21: Time-domain sample of the transmitted signal Perform a Fast Fourier Transform to obtain its spectrum. The calculation method is as follows:

[0015] ;

[0016] S22: Spectrum of time-domain samples of the transmitted signal Performing a conjugate operation yields a matched filter. The calculation method is as follows:

[0017] ;

[0018] In a preferred embodiment of the present invention, step S3 specifically includes:

[0019] S31: Based on satellite platform speed and oblique angle The Doppler frequency shift of the echo signal is calculated using the following method:

[0020] ;

[0021] S32: Based on the Doppler frequency caused by platform motion The constructed matched filter is shifted to align with the echo signal spectrum. The shifted matched filter... The calculation method is as follows:

[0022] ;

[0023] In a preferred embodiment of the present invention, step S4 specifically includes:

[0024] S41: Establish the Taylor window function In the frequency domain, the matched filter After Taylor weighting and windowing, the matched filter is as follows:

[0025] ;

[0026] S42: Receive the spectrum of the signal. Frequency domain of matched filters Multiplying these results yields the spectrum of the compressed product, calculated as follows:

[0027] ;

[0028] S43: Yes Performing an inverse fast Fourier transform back to the time domain yields the final compressed pulse, calculated as follows:

[0029] ;

[0030] As described above, the technical solution adopted in this invention has the following beneficial effects:

[0031] This invention solves the core bottleneck of pulse compression power reduction caused by Doppler frequency offset of high-speed targets in traditional space-based radars when using hourly wide bandwidth signals through innovative frequency domain Doppler precision compensation technology. This method improves radar detection performance: significantly enhancing the signal-to-noise ratio for detecting high-speed, highly maneuverable targets, thereby giving space-based radar systems stronger long-range detection capabilities and more stable target tracking performance. Attached Figure Description

[0032] Figure 1 This is a flowchart of a Doppler tolerance extension method for space-based air detection radar signals according to the present invention.

[0033] Figure 2 This is a schematic diagram of the Doppler frequencies without Doppler shifting in this invention.

[0034] Figure 3 This is a schematic diagram illustrating the degree of peak energy reduction under different Doppler frequency offset conditions according to the present invention.

[0035] Figure 4 This is a schematic diagram of the Doppler frequency for Doppler translation according to the present invention. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] The embodiments provided by the present invention will be described in detail below:

[0038] This embodiment proposes a Doppler tolerance extension method for space-based air detection radar signals. This method corrects Doppler mismatch by performing spectrum shifting on the echo signal, ensuring optimal coherent energy accumulation after pulse compression, thereby effectively solving the peak power reduction problem caused by Doppler frequency offset. This embodiment, through spectrum shifting of the echo signal, solves the problem of peak power reduction after pulse compression, significantly improving the target detection performance of space-based radar in complex dynamic environments.

[0039] like Figure 1 As shown, the present invention provides a signal processing method for space-based radar air detection, comprising the following steps:

[0040] 10) Perform Fast Fourier Transform: Perform Fast Fourier Transform on the received radar echo signal.

[0041] 20) Construct a matched filter: Construct a matched filter based on the transmitted signal and compensate the matched function.

[0042] 30) Spectral shift of the matched filter: The constructed matched filter is shifted to align with the spectrum of the echo signal.

[0043] 40) Perform pulse compression: Multiply the echo signal with the windowed matched filter, and then perform Fourier transform to complete pulse compression.

[0044] As a preferred embodiment, step S1 specifically includes:

[0045] For the received digital echo signal Perform a Fast Fourier Transform to obtain the spectrum of the echo signal. The calculation method is as follows:

[0046] ;

[0047] As a preferred embodiment, step S2 specifically includes:

[0048] S21: Time-domain sample of the transmitted signal Perform a Fast Fourier Transform to obtain its spectrum. The calculation method is as follows:

[0049] ;

[0050] S22: Spectrum of time-domain samples of the transmitted signal Performing a conjugate operation yields a matched filter. The calculation method is as follows:

[0051] ;

[0052] As a preferred embodiment, step S3 specifically includes:

[0053] S31: Based on satellite platform speed and oblique angle The Doppler frequency shift of the echo signal is calculated using the following method:

[0054] ;

[0055] Taking a typical low-Earth orbit satellite platform with a speed of 7600 m / s and an oblique angle of 45° as an example, the maximum Doppler frequency offset is 0.344 MHz.

[0056] S32: Based on the Doppler frequency caused by platform motion The constructed matched filter is shifted to align with the echo signal spectrum. The shifted matched filter... The calculation method is as follows:

[0057] ;

[0058] Taking a short-bandwidth signal with a bandwidth of 2.1MHz and a duration of 4µs, and a Doppler frequency offset of 0.344MHz as an example, during matched filtering, the echo and the matched function are multiplied in the frequency domain. Only the aligned portion of their spectra is accumulated; the misaligned portion becomes zero and cannot be accumulated by pulse compression. For a 2.1MHz bandwidth signal, the Doppler frequency offset of 0.344MHz accounts for 16.4% of the bandwidth. A schematic diagram of the Doppler frequency without Doppler shift is shown below. Figure 2 As shown.

[0059] The degree of peak energy reduction under different Doppler frequency offset conditions is as follows Figure 3 As shown, when the Doppler frequency shift is 0.344MHz, the gain of conventional pulse compression deteriorates by 1.30dB. A schematic diagram of Doppler shift is shown below. Figure 4 As shown, shifting the spectrum of the matched function by one Doppler frequency to align it with the spectrum of the echo signal can reduce the power drop caused by Doppler frequency offset.

[0060] As a preferred embodiment, step S4 specifically includes:

[0061] S41: Establish the Taylor window function In the frequency domain, the matched filter After Taylor weighting and windowing, the matched filter is as follows:

[0062] ;

[0063] S42: Receive the spectrum of the signal. Frequency domain of matched filters Multiplying these results yields the spectrum of the compressed product, calculated as follows:

[0064] ;

[0065] S43: Yes Performing an inverse fast Fourier transform back to the time domain yields the final compressed pulse, calculated as follows:

[0066] ;

[0067] Taking a wide-bandwidth signal with a bandwidth of 2.1MHz and a duration of 4µs as an example, the energy ratio of the pulse compression result after spectrum shifting can reduce the power drop caused by Doppler frequency offset compared with the traditional method. The improved pulse compression gain deteriorates to 0dB, which is 1.30dB worse than the pulse compression gain of the traditional method, and the power is increased by 1.30dB.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for extending the Doppler tolerance of space-based air detection radar signals, characterized in that, Includes the following steps: S1: Perform Fast Fourier Transform on the received radar echo signal. S2: Construct a matched filter. Based on the transmitted signal, construct a matched filter and compensate for the matched function. S3: Perform a spectrum shift on the matched filter to align it with the spectrum of the echo signal. S31: Based on satellite platform speed and oblique angle The Doppler frequency shift of the echo signal is calculated using the following method: ； S32: Based on the Doppler frequency caused by platform motion The constructed matched filter is shifted to align with the echo signal spectrum. The shifted matched filter... The calculation method is as follows: ； S4: Perform pulse compression by multiplying the echo signal with the windowed matched filter and then performing a Fourier transform to complete the pulse compression. S41: Establish the Taylor window function In the frequency domain, the matched filter After Taylor weighting and windowing, the matched filter is as follows: ； S42: Receive the spectrum of the signal. Frequency domain of matched filters Multiplying these results yields the spectrum of the compressed product, calculated as follows: ； S43: Yes Performing an inverse fast Fourier transform back to the time domain yields the final compressed pulse, calculated as follows: 。 2. The Doppler tolerance extension method for space-based air detection radar signals according to claim 1, characterized in that: Step S1 specifically includes: For the received digital echo signal Perform a Fast Fourier Transform to obtain the spectrum of the echo signal. The calculation method is as follows: 。 3. The Doppler tolerance extension method for space-based air detection radar signals according to claim 1, characterized in that: Step S2 specifically includes: S21: Time-domain sample of the transmitted signal Perform a Fast Fourier Transform to obtain its spectrum. The calculation method is as follows: ； S22: Spectrum of time-domain samples of the transmitted signal Performing a conjugate operation yields a matched filter. The calculation method is as follows: 。

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