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An antenna in-situ performance analysis for the hypersonic flight vehicle "HEXAFLY" is presented. Two simulation tools and a Compact Antenna Test Range (CATR) measurement facility are employed to obtain the embedded radiation characteristics of two different antenna systems. In a first step, both antenna types are simulated and measured without the impact of the flight vehicle, but in an environment supporting correct functioning, e.g. on a finite conducting ground plane or on top of a vertical conducting stabilizer. A finite element method (FEM) solver is used for this detailed full-wave analysis of antenna structures with fine geometrical and material details. Next, the FEM solver and a method of moments (MoM) solver with multilevel fast multipole algorithm (MLFMA) acceleration are used to obtain the in-situ radiation characteristic of both antennas mounted on the flight vehicle. The FEM solver is now utilized to simulate the complete setup, whereas the MoM solver works with an equivalent radiation source, which is obtained from CATR measurements of isolated antennas. The results confirm the effectiveness of the measurement data based twostep-approach, which helps to overcome the limitations of pure simulations that are often not feasible for off-the-shelf antennas, and allows the overall validation process to be viewed with added confidence.

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).

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