High-Resolution Squinted SAR Imaging Algorithm Applied in the Near-Field Environment

Shijia Wang,Wanli Liu,Shibo Wang

doi:10.1155/2020/1647957

Shijia Wang, Wanli Liu + Show 1 more

Open Access

https://doi.org/10.1155/2020/1647957

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Journal: Complexity	Publication Date: May 22, 2020
License type: CC BY 4.0

Affiliation: China University of Mining and Technology

Abstract

In the squinted synthetic aperture radar (SAR) imaging of the near-field environment, range-dependent characteristic of squint angle cannot be ignored, which causes azimuth-dependent range cell migration (RCM) after linear range walk correction (LRWC). In this study, an efficient SAR imaging algorithm applied in the near-field environment is proposed. In the processing of the range focusing, LRWC is firstly used to remove the linear RCM. Then, the residual LRCM is expanded into azimuth-invariant and azimuth-variant terms in consideration of the residual LRCM of azimuth-dependent. Range cell migration azimuth scaling (RCMAS) is designed to remove the azimuth-variant term before secondary range compression (SRC) and range compression (RC). In the azimuth focusing, azimuth distortion compensation (ADC) is performed to compensate the azimuth distortion, following which azimuth nonlinear chirp scaling (ANCS) is applied to equalize the frequency modulation (FM) rate for azimuth compression (AC). The simulated results show that more accurate and improved imaging result can be obtained with the proposed algorithm.

Highlights

Due to the ability of high-resolution imaging for the observed scene with any time and any weather, synthetic aperture radar (SAR) has become one of the most attractive radar techniques [1, 2]. ere are many imaging modes for SAR, such as stripmap [3, 4], spotlight [5, 6], and sliding spotlight [7, 8]
Liu et al [16] first used linear range walk correction (LRWC), secondary range compression (SRC), and range compression (RC) to accomplish the range focusing. en, in order to solve the problem of the azimuth-dependent frequency modulation (FM) rate caused by LRWC, a filter function and a scaling function, Complexity called the nonlinear chirp scaling (NCS) algorithm, were constructed
Azimuth-dependent residual linear RCM (LRCM) is removed through range cell migration azimuth scaling (RCMAS) processing. ird, SRC is applied to remove the coupling of range and azimuth

Summary

Introduction

Due to the ability of high-resolution imaging for the observed scene with any time and any weather, synthetic aperture radar (SAR) has become one of the most attractive radar techniques [1, 2]. ere are many imaging modes for SAR, such as stripmap [3, 4], spotlight [5, 6], and sliding spotlight [7, 8]. Azimuth-dependent residual LRCM is removed through range cell migration azimuth scaling (RCMAS) processing. Since the target squint angle varies with the slant range, targets P1, P0, and P2 have different LRCMs. the red dotted line denotes LRWC function. After LRWC processing, the residual LRCMs of targets P3, P0, and P4 located in the same range cell are azimuth-dependent. The residual LRCM and the QRCM and higher-order RCM vary with the target azimuth position. Where Φ(fr, fa) is expressed as (17), and the second exponential term represents the target azimuth position. (38) Substitute (28) into (38); Θ(fa) is approximately (33) expressed as a power series of tn and fa as follows: Transforming (33) into the azimuth time domain yields.

Simulation

Conclusion