Abstract
According to the limitations of single channel Frequency Modulation Continuous Wave (FMCW) Synthetic Aperture Radar (SAR), Digital Beamforming (DBF) technology is introduced to improve system performance. Combined with multiple receive apertures, DBF FMCW SAR can obtain high resolution in low pulse repetition frequency, which can increase the processing gain and decrease the sampling frequency. The received signal model of DBF FMCW SAR is derived. The continuous antenna motion which is the main characteristic of FMCW SAR received signal is taken into account in the whole signal processing. The detailed imaging diagram of DBF FMCW SAR is given. A reference system is also demonstrated in the paper by comparing with a single channel FMCW SAR. The validity of the presented diagram is demonstrated with a point target simulation results.
Highlights
The combination of Frequency Modulated Continuous Wave (FMCW) technology and Synthetic Aperture Radar (SAR) paves a way to light-weight, cost-effective, high-resolution active microwave remote sensing instrument
The noise equivalent sigma zero (NESZ) is a quantity directly related to SAR imaging performance, which is defined as the target Radar Cross Section (RCS) when the Signal Noise Radio (SNR) of the image is equal to one [17]
For Digital Beamforming (DBF) Frequency Modulation Continuous Wave (FMCW) SAR, the impact of continuous motion antenna is negligible during multichannel azimuth reconstructing [15]; it must be considered during range cell migration (RCM) correction
Summary
The combination of Frequency Modulated Continuous Wave (FMCW) technology and Synthetic Aperture Radar (SAR) paves a way to light-weight, cost-effective, high-resolution active microwave remote sensing instrument. In pulsed SAR systems, wide unambiguous swath coverage and high azimuth resolution are contradicting requirements Several proposals, such as multiple beam SAR system operating in a squinted imaging geometry [7], displaced phase center antenna technique [8], quad array system [9], and High-Resolution Wide-Swath (HRWS) SAR system [10], have been presented to resolve the aforementioned dilemma. Those systems have their own advantages and disadvantages.
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