Frequency Scanning Transmit/Receive Antenna Beam Imaging Mode

Abstract:
The SAR imaging mode described in this paper utilizes the available bandwidth to form a narrow frequency-scanning transmit antenna beam 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. The operation parameters of the frequency SCan On Receive and Transmit (fSCORT) technique may be chosen to significantly reduce the duration of the received radar echo without sacrificing swath width. The frequency scanning SAR technique/mode described in this paper is known from [1, 2, 3]. The paper provides a simple model describing the imaging mode. It is shown that the technique trades range resolution for signal-to-noise ratio, azimuth resolution, and swath width. Further, 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. The imaging mode is especially suitable for spaceborne SAR systems operating at high frequencies, where other advanced digital beam-forming techniques may not be feasible due to technology limitations. The performance metric of the technique is derived, and a comparison to classical stripmap operation mode shows an improvement of several decibels.