Synthetic Aperture Radar Frequency Scan for Time-of-Echo Compression Imaging Mode

Abstract

The paper details a SAR imaging mode named frequency SCan On Receive and Transmit (fSCORT) where, a narrow, frequency-scanning transmit antenna beam is formed illuminating the swath of interest from far to near range. Similarly, the frequency-scanning receive antenna beam collects the return echo signal reflected from the ground. It is shown that the imaging technique trades (sacrifices) range resolution for (improved) signal-to-noise ratio, azimuth resolution, and swath width. It is shown that the (transmit) pulse duty cycle may be significantly increased over what is common for pulsed SAR systems, allowing for a lower peak-to-average transmit power ratio. A comparison to classical stripmap operation mode shows an improvement of several decibels. The imaging mode is especially suitable for spaceborne SAR systems operating at high carrier frequencies where other advanced digital beam-forming techniques may not be feasible due to technology limitations, while, on the other hand, a large system bandwidth may be available. The final paper provides a simple mathematical model describing fSCORT operation modes. Closed expressions for the mode performance parameters, such as range resolution, echo window length, signal-to-noise ratio, etc.\ are derived. The performance of fSCORT is compared to a SAR operating in stripmap and SCORE mode.