Reducing micro‐Doppler effect in compressed sensing ISAR imaging for aircraft using limited pulses

Abstract

In compressed sensing (CS)-based inverse synthetic aperture radar (ISAR) imaging for aircraft, the image of the target can be reconstructed using fewer pulses with random pulse repetition intervals than with the conventional range-Doppler (RD) method. However, the micro-Doppler (mD) effect induced by the non-stationary parts of aircraft still causes defocusing as in RD imaging. A method is proposed to reduce the mD effect in CS ISAR imaging. The CS-based short-time Fourier transform is deployed to reconstruct the time-frequency (TF) spectrogram of echoes. An L-statistics-based algorithm is applied to separate the non-stationary scatterers from a rigid main body in the TF domain. Furthermore, the CS algorithm is used to reconstruct the cross-range image of the main body after mD separation. Compared with direct CS imaging without mD removal, a better image can be obtained. The results of both simulated and real data processing demonstrate the validity of the proposed method.Introduction: In inverse synthetic aperture radar (ISAR) imaging for aircraft, the images are usually contaminated because of the micro-Doppler (mD) effect, which is induced by the non-stationary mechanical structures such as the rotating blades in helicopters and the propellers or turbofans in airplanes. Some mD separating methods based on time-frequency (TF) analysis have been proposed and proved to be effective in conventional range-Doppler (RD) imaging [1,2].Different from RD imaging, compressed sensing (CS) ISAR imaging can reconstruct the image of the target using much fewer pulses with random pulse repetition intervals (PRIs) [3]. However, how to remove the mD effect in CS ISAR imaging is still an open problem. Since the existing mD extracting methods require that the echoes of targets are uniformly sampled in the cross-range dimension, the validity of these methods is challenged in random sampling. To solve this problem, in this Letter we propose a method to reduce the mD effect for CS ISAR imaging.

Micro‐Doppler effect removal for inverse synthetic aperture radar imaging based on augmented Lagrange multipliers

“…. According to (7), the echo with regard to slow-time t under the range unit r 1 can be expressed as…”

“…Another type reduces MD effect by using time-frequency analysis (TFA). [3][4][5][6][7][8][9] Different from HT or RT, these methods extract the MD effect in the spectrogram of range profile. However, the experimental results are sensitive to image resolution, resulting in a fluctuating performance once the rotating radius of a micro-motion scatterer is smaller than the half of range resolution.…”

Micro-Doppler Effect Removal in ISAR Imaging by Promoting Joint Sparsity in Time-Frequency Domain

“…The L-statistics-based method is combined with the short-time compressed sensing (STCS) [ 11 ] approach in Q.K. Hou et al [ 12 ] to reduce the m-D effect with limited pulses. The STCS was employed to recover the STFT entries where the number of the frequency bins was equal to the number of full pulses.…”

“…As a result, the L-statistics-based method in Q.K. Hou et al [ 12 ] cannot obtain the accurate support of the main body signal in the frequency dimension and some spurious points exist near the main body scatterers in the imaging result.…”

An Isar Imaging Method for Search Radar Involving Nonuniform Angle Samples

“…To obtain clear ISAR images from a signal with nonuniform angle samples, compressed sensing (CS) based approaches can be used [8][9][10][11][12][13]. However, CS-based approaches have two major drawbacks.…”