A Novel ISAR Imaging Method for Maneuvering Target Based on AM-QFM Model Under Low SNR Environment

Li Li,Li Yan,Dong Li,Hongqing Liu,Chengxiang Zhang

doi:10.1109/access.2019.2943576

Abstract

Inverse synthetic aperture radar (ISAR) imaging for long range maneuvering small/stealth target plays an important role in the field of national defense surveillance. Due to low signal-to-noise (SNR) of received echo signal and the nonstationary Doppler frequency modulated (DFM) during the coherent processing intervals (CPI), the conventional range-Doppler (RD) algorithm is unsuitable to generate a well-focused ISAR image. Furthermore, the dihedral or trihedral components of the maneuvering target or range cell migration caused by the target's complex motion generate the time-varying amplitudes for the received signal, which brings a new challenge for ISAR imaging algorithm design. To overcome those issues, in this work, we propose a new method to obtain the well-focused ISAR image of long range maneuvering small/stealth target. This method consists of two main steps. First, the received signal in a range bin is characterized as multicomponent amplitude modulated-quadratic frequency modulated (AM-QFM) signal with time-varying amplitudes after the translational compensation. After that, a novel coherently integrated general cubic phase function (CIGCPF) is developed to estimate the parameters of multi-component AM-QFM signal. Compared with the existing ISAR imaging methods based on the constant amplitude signal model during the CPI, the well-focused ISAR image can be obtained by the proposed method with time-varying amplitude in a low SNR environment. Finally, the simulation results demonstrate the effectiveness of the proposed algorithm.

Highlights

Inverse synthetic aperture radar (ISAR) has been widely used in many fields of civil and military applications because it has the ability to produce high-resolution images regardless the weather conditions [1]–[3]
Compared with the integrated GCPF (IGCPF)-ICPF method, the proposed method has a slightly lower computational complexity since the fast non-uniform FFT (NUFFT) is utilizing, which benefits from the real-time realization and engineering applications for maneuvering target imaging in the low SNR environment
The azimuth Doppler frequency has modulation characteristics, which makes the target image defocused by using the traditional RD algorithm based on Fourier transform (FT) transform

Summary

INTRODUCTION

Inverse synthetic aperture radar (ISAR) has been widely used in many fields of civil and military applications because it has the ability to produce high-resolution images regardless the weather conditions [1]–[3]. Utilizing the QFM model, a large number of ISAR imaging algorithms have been proposed recently to obtain well-focused ISAR image for a maneuvering target [16]–[23] Those kinds of methods usually require high SNR and they only assume the case where the received echo signal has constant amplitude during the integrated imaging interval. In [24], considering the time-varying characteristics of amplitude, a novel Dechirp and parameter estimation (DAPE) based method is developed with the second-order LFM signal model It is suitable for the target with moderate maneuverability, and the ISAR image obtained will appear to be defocused and smeared for the maneuvering target as has been introduced previously.

ISAR IMAGING GEOMETRY AND SIGNAL MODEL

PARAMETER ESTIMATION OF TIME-VARYING AMPLITUDE QFM SIGNAL

EXPERIMENTAL RESULTS AND ANALYSIS

CONCLUSION