On Predistortion Filtering for Switched Beamforming With Phased-Array Antennas

In recent work on channel sounding, we proposed switching the antennas of phased arrays and beamforming in postprocessing – what we coined switched beamforming – instead of scanning beams through analog beamforming – what the arrays are designed for. Not only is switched beamforming orders of magnitude quicker than analog beamforming, it also synthesizes beam patterns that are quasi-ideal. In the same work, we proposed predistortion filtering to calibrate the channel sounder by designing a separate filter for each of the switched antennas. It was later found that the design neglects the mutual leakage between the antennas on the printed circuit board. In this paper, we propose an improved design that considers all antennas collectively to account for the leakage. Not only does it increase the peak-to-sidelobe ratio of the channel impulse response by up to 21 dB, the response is also stable across the range of beamformed angles.