Strabismus high-orbit SAR non-stop phase modulation compensation method and device

Abstract

The invention provides a squint high-orbit SAR non-stop phase modulation compensation method and device, and relates to the technical field of synthetic aperture radar signal processing. The method comprises the steps that under satellite-ground continuous motion, a slope distance model of radar pulses from transmitting to receiving is established, and the slope distance model is related to changes of fast time; the method comprises the following steps: presetting a transmitted pulse of a radar as a linear frequency modulation signal, and performing orthogonal demodulation on the linear frequency modulation signal according to a slope distance model to obtain a baseband echo signal of a point target in a two-dimensional time domain; fourier transform is carried out on the baseband echo signal to obtain a two-dimensional frequency domain echo signal and a two-dimensional frequency domain modulation phase caused by satellite-ground continuous motion; preprocessing the two-dimensional frequency domain modulation phase to preliminarily compensate the two-dimensional frequency domain modulation phase; and sequentially performing imaging processing and post-processing on the preprocessed two-dimensional frequency domain echo signal, and performing secondary compensation on a two-dimensional frequency domain modulation phase to obtain a target echo signal in a distance Doppler domain.

Description

technical field [0001] The present disclosure relates to the field of synthetic aperture radar (Synthetic Aperture Radar, SAR) signal processing technology, in particular to the field of spaceborne synthetic aperture radar imaging processing technology, and more specifically to a squint high orbit SAR non-stop phase modulation compensation method and device. Background technique [0002] With the development of spaceborne SAR technology, a remote sensor that places SAR payloads on geosynchronous orbit satellites has become an emerging research hotspot in the field of SAR. Compared with low-orbit SAR, geosynchronous orbit SAR has the advantages of large coverage, short revisit period, strong anti-strike and anti-destroy capabilities, and has very broad application prospects in both civilian and military fields. [0003] Spaceborne SAR adopts a pulse system to transmit and receive signals at a fixed pulse repetition frequency (Pulse Repeat Frequency, PRF). The SAR signal prop...

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Problems solved by technology

Therefore, if the imaging method of low-orbit SAR is directly used, it will be difficult to achieve precise focusing of geosynchronous orbit SAR.

[0005] In terms of squint high-orbit SAR stop-go phase modulation compensation, there are two main problems in the existing technology: first, for high-orbit satellites, the stop-go hypothetical model is no longer applicable, and the general spaceborne SAR two-dimensional time-domain echo signal model The description is not precise enough; second, the method of intra-pulse stop-and-go error compensation is not simple enough

[0006] (1) The existing technology is based on the stop-and-go assumption, and does not consider the change of the platform movement distance and the change of the slant distance with fast time within a few or even dozens of pulses between pulse transmission and reception

[0007] (2) The existing technology uses mathematical approximations such as linear partial derivatives in the derivation of the transmit slant distance and the receive slant distance, and simplifies the unary high-order equation into a linear equation for solution. Although the calculation process is simple, additional errors are introduced

[0008] (3) The existing technology is often combined with a specific imaging algorithm processing flow when compensating the error caused by the "stop-go" assumption, which is not universal

[0009] Therefore, the existing technical solutions are not comprehensive enough to consider the continuous motion of the satellite in the squint high-orbit satellite, which makes the two-dimensional time-domain echo signal model of the squint high-orbit SAR inaccurate, thus causing modulation phase errors, and the error It will be aggravated with the increase of synthetic aperture time, the increase of squint imaging angle, and the increase of satellite orbit altitude, which will affect the precise focus

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