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  • Research Article
  • Open Access

An Analysis of ISAR Image Distortion Based on the Phase Modulation Effect

EURASIP Journal on Advances in Signal Processing20062006:083727

  • Received: 28 April 2005
  • Accepted: 16 December 2005
  • Published:


Distortion in the ISAR image of a target is a result of nonuniform rotational motion of the target during the imaging period. In many of the measured ISAR images from moving targets, such as those from in-flight aircraft, the distortion can be quite severe. Often, the image integration time is only a few seconds in duration and the target's rotational displacement is only a few degrees. The conventional quadratic phase distortion effect is not adequate in explaining the severe blurring in many of these observations. A numerical model based on a time-varying target rotation rate has been developed to quantify the distortion in the ISAR image. It has successfully modelled the severe distortion observed; the model's simulated results are validated by experimental data. Results from the analysis indicate that the severe distortion is attributed to the phase modulation effect where a time-varying Doppler frequency provides the smearing mechanism. For target identification applications, an efficient method on refocusing distorted ISAR images based on time-frequency analysis has also been developed based on the insights obtained from the results of the numerical modelling and experimental investigation conducted in this study.


  • Rotation Rate
  • Rotational Motion
  • Doppler Frequency
  • Target Identification
  • Image Distortion

Authors’ Affiliations

Defence R&D Canada - Ottawa, 3701 Carling Avenue, Ottawa, ON, K1A 0Z4, Canada


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© Wong et al. 2006