Over-The-Air Calibration of a Dual-Beam Dual-Polarized 28-GHz Phased-Array Channel Sounder

This paper describes an over-the-air (OTA) calibration procedure for the impulse response of a 28-GHz phased-array antenna channel sounder. The silicon-germanium (SiGe) antenna board is composed from two 8×8 planar arrays; each array can generate a distinct beam in the vertical and horizontal polarizations that can be steered in both azimuth and elevation within ±50° and ±25°, respectively. As part of the calibration procedure, unique pre-distortion filters were designed per steer angle, achieving a peak-to-sidelobe ratio in the impulse response of up to 56.5 dB, with less than 1 dB variation across the steer angles. Critically, we show that performance degraded up to 10.1 dB when applying the pre-distortion filter designed at one steer angle to the other steer angles, underscoring the need for angle-specific filters. Finally, we show that performance between both polarizations is comparable thanks to the array symmetries in the fabrication process.