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Advanced spaceborne SAR systems with planar antenna

Synthetic aperture radar (SAR) remote sensing allows high-resolution imaging independent of weather conditions and sunlight illumination and is therefore very attractive for the systematic observation of dynamic processes on the Earth's surface. Conventional spaceborne SAR systems are, however, limited in that a wide swath can only be imaged at the expense of a degraded azimuth resolution. This limitation can be overcome by using SAR systems with multiple receive subapertures displaced in along-track, ScanSAR systems with multiple azimuth channels, or multiple elevation beam SAR systems, which use digital beamforming (DBF) on receive for simultaneous mapping of multiple subswaths. In the latter case, a combined transmit-receive planar phased array antenna can be employed, using phase-only tapering to form a wide transmit beam, while exploiting all the available power and ensuring the best possible efficiency of the high power transmit modules. A parametric closed-form expression for the phase tapers can be analytically derived, which result in a wide transmit beam optimized for noise and ambiguity performance.