Trajectory instabilities and onboard navigation system characteristics influence on synthetic aperture radar image quality

DOI: 10.34759/trd-2022-125-14

Аuthors

Kamensky K. V.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

e-mail: kvkmai@mail.ru

Abstract

The goal of this work is to determine requirements imposed on onboard navigation system for the radar that is to be placed on a small unmanned aerial vehicle and to work in stripmap side-looking synthetic aperture mode with linear frequency modulated continuous wave. To achieve this goal the methodology is proposed to investigate trajectory instabilities effects on radar image in continuous wave synthetic aperture radar. The same methodology can be used to obtain the estimates of onboard navigation system characteristics impact on radar image quality. These characteristics are: measurement accuracy of radar antenna system phase center coordinates and data sampling frequency. The proposed methodology is based upon the use of backprojection method to process a track signal obtained through direct simulation in the condition that there is only one point reflector on the illuminated scene. Quality of the amplitude radar image obtained this way can be estimated by objective criteria: main lobe width and side lobes relative level in the point reflector’s response. The results of the proposed methodology implementation are estimates used to choose the onboard navigation system for a specific radar. In this paper the cases were investigated where trajectory instabilities are absent, represent a constant value, a linear function, or a non-linear function (sinusoid). It is concluded that onboard navigation system data sampling frequency should be not less than track signal sampling frequency in slow time, and acceptable accuracy of coordinate measurement depends on expected intensity of trajectory instabilities. The practical value of the conducted work is in that the proposed methodology allowed to provide rationale for requirements imposed on the onboard navigation system characteristics.

Keywords:

synthetic aperture radar, backprojection, track signal, continuous wave, linear frequency modulation

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