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CN-121978691-A - Ultra-wideband impulse SAR standing wave suppression method and device

CN121978691ACN 121978691 ACN121978691 ACN 121978691ACN-121978691-A

Abstract

The invention provides a method and a device for restraining standing waves of ultra-wideband impulse SAR, which relate to the field of radars and comprise the steps of acquiring echo data through ultra-wideband impulse SAR scanning and preprocessing the data; the method comprises the steps of carrying out two-dimensional SAR imaging by using preprocessed echo data to obtain a two-dimensional SAR image with standing waves, selecting a non-matching frequency range according to a standing wave signal frequency model and antenna actual parameters, removing the non-matching frequency range from a distance spectrum of the two-dimensional SAR image, extrapolating the removed frequency components by using an energy weighted least square method to obtain a complete distance spectrum, carrying out certain amplitude weighting on the extrapolated distance spectrum, and then converting the extrapolated distance spectrum back to an image domain to obtain the two-dimensional SAR image after standing wave suppression. According to the method, the unmatched frequency components are discarded in the distance spectrum of the two-dimensional SAR image, so that the unmatched signal components are restrained, and then the spectrum leakage and the distance resolution loss caused by removing the frequency components are solved through spectrum extrapolation.

Inventors

  • TANG HAIBO
  • CHEN LONGYONG
  • ZHANG FUBO
  • XU XINHAO
  • LI WENJIE
  • ZHANG CHENGWEI

Assignees

  • 中国科学院空天信息创新研究院

Dates

Publication Date
20260505
Application Date
20260407

Claims (10)

  1. 1. The ultra-wideband impulse SAR standing wave suppression method is characterized by comprising the following steps of: step 1, acquiring echo data through ultra wideband impulse SAR scanning, and preprocessing the data; Step 2, performing two-dimensional SAR imaging by using the preprocessed echo data to obtain a two-dimensional SAR image with standing waves; Step 3, selecting a non-matching frequency range according to the standing wave signal frequency model and the actual parameters of the antenna, and removing the non-matching frequency range in a distance spectrum of the two-dimensional SAR image; Step 4, extrapolation is carried out on the removed frequency components by using an energy weighted least square method to obtain a complete distance spectrum; And step 5, carrying out certain amplitude weighting on the externally-deduced distance spectrum, and then converting the obtained distance spectrum back to an image domain to obtain a two-dimensional SAR image after standing wave suppression.
  2. 2. The method for suppressing ultra-wideband impulse SAR standing waves as claimed in claim 1, wherein, In step 1, an impulse SAR system is used for scanning a scene to be imaged to obtain original echo data Wherein The distance is indicated to be fast to the time, Preprocessing the echo data, converting the signal from real signal to complex signal using Hilbert transform: 。
  3. 3. the method for suppressing ultra-wideband impulse SAR standing waves as claimed in claim 2, wherein, In the step 2, a time domain imaging algorithm is adopted to perform two-dimensional imaging, specifically: ; Wherein, the Is shown in the first The radar echo signals of the individual square points, For the total number of square points, Is the azimuth position and imaging point A two-way delay between; Is a two-dimensional SAR imaging result with standing waves.
  4. 4. The method for suppressing ultra-wideband impulse SAR standing waves as claimed in claim 3, wherein, In step 3, firstly, a frequency model of the standing wave signal is established, the collected echo is expressed as superposition of an ideal signal and the standing wave signal, and the frequency spectrum expression is as follows: ; Wherein, the Is ideally free of standing wave signals Is used for the spectrum of the (c), Is the frequency spectrum of the standing wave signal, wherein For the delay of the standing wave signal from the ideal signal in the time domain, Representing the amplitude of the standing wave signal under different frequency components; Operating frequency of antenna Performing Fourier transform on the two-dimensional SAR imaging result in the distance direction to obtain a distance spectrum, and setting the frequency band to zero: ; the obtained distance spectrum 。
  5. 5. The method for suppressing ultra-wideband impulse SAR standing wave as claimed in claim 4, wherein, In step 4, distance spectrum Is expressed as a vector The measured spectrum, which is the energy weighted least squares, is expressed as: ; Wherein the method comprises the steps of For the spectrum to be extrapolated, For a special fourier transform matrix, expressed as: ; ; Wherein the method comprises the steps of Is the set of numbers corresponding to the selected frequency, Is the azimuth total point number.
  6. 6. The method for suppressing ultra-wideband impulse SAR standing wave as claimed in claim 5, wherein, Step 4 further comprises the spectral extrapolation process expressed as: ; ; Wherein, the Representing the extrapolation solution, Form a diagonal weight matrix Representing the standard inner product in Hilbert space, deriving from the projection theorem: ; thus obtaining the distance spectrum of the ideal two-dimensional SAR image without standing waves.
  7. 7. The method for suppressing ultra-wideband impulse SAR standing waves as claimed in claim 6, wherein, In step 5, the average amplitude ratio of the original spectrum to the extrapolated spectrum is calculated: ; weighting according to the ratio to obtain a distance spectrum of the two-dimensional SAR image to be solved: ; finally, obtaining a two-dimensional SAR image after standing wave suppression through inverse Fourier transform: 。
  8. 8. An ultra-wideband impulse SAR standing wave suppression device, comprising: the data acquisition module acquires echo data through ultra-wideband impulse SAR scanning and performs data preprocessing; The imaging module is used for carrying out two-dimensional SAR imaging by using the preprocessed echo data to obtain a two-dimensional SAR image with standing waves; The removing module is used for selecting a non-matching frequency range according to the standing wave signal frequency model and the antenna actual parameters and removing the non-matching frequency range in the distance spectrum of the two-dimensional SAR image; The extrapolation module extrapolates the removed frequency components by using an energy weighted least square method to obtain a complete distance spectrum; and the result generation module performs certain amplitude weighting on the externally-deduced distance spectrum and then transforms the obtained distance spectrum back to an image domain to obtain a two-dimensional SAR image after standing wave suppression.
  9. 9. An electronic device comprising one or more processors and a memory for storing one or more programs, wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the method of any of claims 1-7.
  10. 10. A computer readable storage medium having stored thereon executable instructions which when executed by a processor cause the processor to implement the method of any of claims 1 to 7.

Description

Ultra-wideband impulse SAR standing wave suppression method and device Technical Field The invention relates to the technical field of radars, in particular to a method and a device for restraining ultra-wideband impulse SAR standing waves. Background The impulse radar is used as a typical ultra-wideband radar system, and obtains extremely large instantaneous bandwidth by transmitting a narrow pulse signal with the magnitude of nanoseconds or picoseconds, so as to realize extremely high range resolution, which provides a technical basis for high-precision imaging of the synthetic aperture radar. However, it is known from the theory of antenna impedance matching that the input impedance of an antenna is a complex frequency function, and when a broadband signal is radiated, the real part and the imaginary part of the impedance vary drastically with frequency, making it difficult to achieve full-band matching with a single circuit. This may lead to degradation of standing waves, which may be accompanied by a secondary signal with a similar frequency component at a fixed distance behind the primary signal, thereby causing ringing, false targets, etc., and affecting subsequent signal processing procedures such as target detection, target identification, etc. In terms of hardware, resistive loading techniques are often used to extend the operating bandwidth of an antenna, i.e., deliberately connecting a resistor in series or parallel at a suitable location (e.g., the middle or end of a transducer) of the antenna to actively and controllably dissipate a portion of the energy and thereby change the performance parameters of the antenna. However, this approach inevitably results in energy loss, which means that for a transmitting antenna, a larger power amplifier power is required to achieve the same radiated power, and for a receiving antenna, a signal to noise ratio is reduced. In terms of signal processing, there are only a few studies on radar standing wave suppression, and these studies are all based on a time domain model of a standing wave signal, which is considered to be a signal identical to the main signal except for amplitude. In practice, the ultra wideband signal is only mismatched in a part of frequency bands, and the frequency component of the standing wave signal is not identical to that of the main signal, so that the existing model is mismatched. Disclosure of Invention In order to solve the technical problems, the invention provides the ultra-wideband impulse SAR standing wave suppression method and the device, which can well suppress the influence caused by standing waves in a two-dimensional SAR image. According to the method, the unmatched frequency components are discarded in the distance spectrum of the two-dimensional SAR image, so that the unmatched signal components are restrained, and then the spectrum leakage and the distance resolution loss caused by removing the frequency components are solved through spectrum extrapolation. The specific technical scheme is as follows: the ultra-wideband impulse SAR standing wave suppression method comprises the following steps: step 1, acquiring echo data through ultra wideband impulse SAR scanning, and preprocessing the data; Step 2, performing two-dimensional SAR imaging by using the preprocessed echo data to obtain a two-dimensional SAR image with standing waves; Step 3, selecting a non-matching frequency range according to the standing wave signal frequency model and the actual parameters of the antenna, and removing the non-matching frequency range in a distance spectrum of the two-dimensional SAR image; Step 4, extrapolation is carried out on the removed frequency components by using an energy weighted least square method to obtain a complete distance spectrum; And step 5, carrying out certain amplitude weighting on the externally-deduced distance spectrum, and then converting the obtained distance spectrum back to an image domain to obtain a two-dimensional SAR image after standing wave suppression. Preferably, in step 1, an impulse SAR system is used to scan a scene to be imaged to obtain original echo dataWhereinThe distance is indicated to be fast to the time,Preprocessing the echo data, converting the signal from real signal to complex signal using Hilbert transform: 。 Preferably, in step 2, a time domain imaging algorithm is used for two-dimensional imaging, specifically: ; Wherein, the Is shown in the firstThe radar echo signals of the individual square points,For the total number of square points,Is the azimuth position and imaging pointA two-way delay between; Is a two-dimensional SAR imaging result with standing waves. Preferably, in step3, a frequency model of the standing wave signal is first established, the collected echo is represented as a superposition of an ideal signal and the standing wave signal, and the spectrum expression is as follows: ; Wherein, the Is ideally free of standing wave signalsIs used for the spectrum of t