In this work, a novel rotation approach for the antenna elements of a linear phased array is presented. The proposed method improves by up to 14 dB the cross-polarization level within the main beam by performing a sequential 90° rotation of the identical array elements, and achieving measured cross-polarization suppressions of 40 dB. This configuration is validated by means of simulation and measurements of a manufactured linear array of five dual-polarized cavity-box aperture coupled stacked patch antennas operating in L-Band, and considering both uniform amplitude and phase distribution and beamforming with amplitude tapering. The analysis is further extended by applying and comparing the proposed design with the 180° rotation and non-rotation topologies. This technique is expected to be used for the next generation L-Band Airborne Synthetic Aperture Radar Sensor of the German Aerospace Center (DLR).

The Microwaves and Radar Institute at the German Aerospace Center (DLR) operates an airborne versatile multi-frequency SAR sensor (F-SAR). Due to the applications of remote-sensing imaging at low frequencies, a new dual polarized L-Band antenna system for the next generation sensor is presented in this paper. Despite the restricted size of the used aircraft, the new antenna optimizes the available space in the antenna carrier by providing more antenna elements, in comparison with the current L-Band sensor, without increasing the inter-element mutual coupling and thereby enhancing the radiation properties of the antenna.

In this work, a new ultra-wideband Grounded Coplanar Waveguide to Substrate Integrated Waveguide transition is presented. The proposed design improves the performance of the triangular tapered slot transition, by providing a return loss level better than 28 dB in the X-Band frequency range (with enhancements of up to 29 dB at higher frequencies in such a band), and a flatter response for the insertion losses. The analysis of the new transition is performed using a dielectric material with high permittivity (εr = 9.8) which leads to an extremely compact implementation. In order to validate the proposed design, several back-to-back transitions with different lengths were manufactured, measured and compared with the simulated data. Further experimental results, after performing an additional Thru-Reflect-Line calibration for de-embedding undesired effects of involved connectors, are also shown.

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Phased array antennas are often built from sub-arrays with identical or symmetrical layout. At an early project stage, performance verification measurements of the sub-array are valuable to proof the single module design. However, the characteristics of the final antenna are questionable without further processing. This work presents a concept that is based on far-field measurements of a sub-array in a Compact Antenna Test Range (CATR) in conjunction with planar near-field (PNF) processing to synthesize the entire phased array antenna characteristics. The procedure is explained with an example of a dual linear polarized L-band planar phased array antenna for an airborne synthetic aperture radar application. It is shown that the measured sub-array can be complemented by the synthesized twin to evaluate the characteristics of a final antenna that is not yet available in this form. The resulting performance of the synthesized entire phased array is presented and compared with simulations. The presented post-processing method would be beneficial to characterizing radiation patterns of large phased arrays by measuring only sub-arrays in a limited test-zone with any measurement principle.