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Open AccessArticle

Application of S-Transform in ISAR Imaging

School of Electronic Engineering, Xidian University, Xi’an 710126, China
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Electronics 2019, 8(6), 676; https://doi.org/10.3390/electronics8060676
Received: 25 April 2019 / Revised: 6 June 2019 / Accepted: 11 June 2019 / Published: 14 June 2019
In inverse synthetic aperture radar (ISAR) imaging, time-frequency analysis is the basic method for processing echo signals, which are reflected by the results of time-frequency analysis as each component changes over time. In the time-frequency map, a target’s rigid body components will appear as a series of single-frequency signals in the low-frequency region, and the micro-Doppler components generated by the target’s moving parts will be distributed in the high-frequency region with obvious frequency modulation. Among various time-frequency analysis methods, S-transform is especially suitable for analyzing these radar echo signals with micro-Doppler (m-D) components because of its multiresolution characteristics. In this paper, S-transform and the corresponding synchrosqueezing method are used to analyze the ISAR echo signal and perform imaging. Synchrosqueezing is a post-processing method for the time-frequency analysis result, which could retain most merits of S-transform while significantly improving the readability of the S-transformation result. The results of various simulations and actual data will show that S-transform is highly matched with the echo signal for ISAR imaging: the better frequency-domain resolution at low frequencies can concentrate the energy of the rigid body components in the low-frequency region, and better time resolution at high frequencies can better describe the transformation of the m-D component over time. The combination with synchrosqueezing also significantly improves the effect of time-frequency analysis and final imaging, and alleviates the shortcomings of the original S-transform. These results will be able to play a role in subsequent work like feature extraction and parameter estimation. View Full-Text
Keywords: time-frequency analysis; S-transformation; ISAR; micro-Doppler; synchrosqueezing time-frequency analysis; S-transformation; ISAR; micro-Doppler; synchrosqueezing
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Zang, B.; Zhu, M.; Zhou, X.; Zhong, L. Application of S-Transform in ISAR Imaging. Electronics 2019, 8, 676.

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