Phase Error Calculation Caused by Start-Stop Approximation in Processing FMCW Radar Signals for SAR Imaging

Abstract

The current synthetic aperture radar (SAR) image formation algorithms have been developed for pulse radar systems, and they are desired for use in for frequency-modulated continuous wave (FMCW) radar systems. Since there is a difference between the outputs of pulse radar and FMCW radar, it is necessary to adapt these algorithms to the output of the pulse radar. In addition, the start-stop approximation, which can be used for the signal processing of pulse radar systems, should be taken into account for FMCW radar systems because the pulse duration of the pulse radar is relatively small in comparison to the modulation time of the FMCW radar. In this study, the phase error caused by the start-stop approximation in processing the data measured by an FMCW radar system for synthetic aperture imaging is investigated. The important results of this study indicate that the start-stop approximation is valid for processing FMCW SAR data in many cases. If the following circumstances occur simultaneously, such as a high radar signal frequency, long modulation time, high platform speed, and short propagation range, then the approximation may become invalid. The simulations and experiments performed with a wideband 154 GHz FMCW radar support this statement.INDEX TERMS FMCW, ramp duration, phase error, back-projection.

A Modified Algorithm for Highly Squinted Missile-Borne SAR Imaging With Large Acceleration

“…t is the time when the beam is pointing to the target, c is the light velocity, 0 f is the carry frequency and r K is the chirp rate. The range Fourier transform is implemented in (5), and then we can get…”

“…Synthetic aperture radar (SAR) is one of the high-resolution imaging radars, which can acquire clear two-dimensional images of the ground area [1]- [5]. Since spaceborne SAR was first launched in 1978, the imaging algorithms of SAR have been developed for many years [6]- [10].…”