Abstract
Narrow-band interference (NBI) and Wide-band interference (WBI) are critical issues for synthetic aperture radar (SAR), which degrades the imaging quality severely. Since some complex signals can be modeled as linear frequency modulated (LFM) signals within a short time, LFM-WBI and NBI are mainly discussed in this paper. Due to its excellent energy concentration and useful properties (i.e., auto-terms pass through the origin of Delay-Doppler plane while cross-terms are away from it), a novel nonparametric interference suppression method using Delay-Doppler iterative decomposition algorithm is proposed. This algorithm consists of three stages. First, we present signal synthesis method (SSM) from ambiguity function (AF) and cross ambiguity function (CAF) based on the matrix rearrangement and eigenvalue decomposition. Compared with traditional SSM from Wigner distribution (WD), the proposed SSM can synthesize a signal faster and more accurately. Then, based on unique properties in Delay-Doppler domain, a mask algorithm is applied for interference identification and extraction using Radon and its inverse transformation. Finally, a signal iterative decomposition algorithm (IDA) is utilized to subtract the largest interference from the received signal one by one. After that, a well-focused SAR imagery is obtained by conventional imaging methods. The simulation and measured data results demonstrate that the proposed algorithm not only suppresses interference efficiently but also preserves the useful information as much as possible.
Highlights
Synthetic aperture radar (SAR) has become an important instrument for earth mapping and been widely utilized in both military surveillance and civilian exploration
In terms of ratio of the interference bandwidth to the useful signal, interference is generally categorized into two groups: narrowband interference (NBI, the ratio is smaller than 1%) and wideband interference (WBI, the ratio is greater than 1%)
We mainly focus on the linear frequency modulated (LFM) Wide-band interference (WBI) (LFM-WBI), since some complex signal can be modeled as an LFM signal within a short time
Summary
Synthetic aperture radar (SAR) has become an important instrument for earth mapping and been widely utilized in both military surveillance and civilian exploration. They employ spectral estimation to distinguish the interference and design a proper filter to remove it in the frequency domain These methods work based on the assumption that only a fraction of frequency bins of NBI are overlapped with that of useful signals. Similar to the parametric methods in NBI suppression, model mismatch and parameter estimation error may lead to great degradation of the SAR image quality. The proposed algorithm has three advantages: (1) both AF and CAF have excellent energy concentration; (2) auto-terms of interferences are more identified and extracted in the AF and CAF domains due to their useful properties; and (3) SSM from AF and CAF is faster and more accurate than the traditional SSM from WD.
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