Highly Integrated Low-Profile Multilayer Dual-Polarized Phased Array Antenna With Truncated Cavities for First Pulsed Bistatic L-Band Airborne SAR Sensor

Synthetic Aperture Radar (SAR) has become, nowadays, one of the most important techniques in remote-sensing, and the increasing interest in Earth monitoring reinforces this trend. Next-generation SAR sensors will enhance the radar resolution capabilities by means of digital beamforming (DBF) techniques along with multistatic systems. In order to support the technological development of future spaceborne SAR missions, airborne sensors become an essential scope of research. Thereby, future airborne SAR systems demand enhanced DBF capabilities that involve phased array antennas with a high density of array elements. However, the antenna aperture size is significantly limited in airborne applications, which leads to low-profile and highly integrated antenna solutions, becoming a more challenging task for lower frequency operations such as L-band. In this work, a compact L-band dual-polarized multilayer phased array antenna with beam steering in elevation, developed for the next-generation German Aerospace Center (DLR) airborne SAR system, is presented. The proposed design makes use of truncated cavities to improve the array element isolation and provides 66% more antenna elements than the previous L-band phased array of the current DLR airborne SAR sensor with the same antenna aperture size. Measurements of a manufactured prototype show an antenna bandwidth of almost 20%, matching levels better than 17 dB, up to 15 dB gain, and cross-polarization suppression values higher than 35 dB. Thus, the proposed work will allow the application of advanced DBF techniques in the upcoming first pulsed bistatic L-band airborne SAR sensor.