Frequency-Selective Beamforming Array Antenna Systems with Frequency-Dependent Phase Shifters

A frequency-selective beamforming array antenna system is proposed for next-generation mobile applications. Whereas a conventional phased array steers antenna beams in the same direction, the proposed system involves a channel-selective beam for each frequency channel using RF/analog processing. A frequency-dependent phase shifter is designed with controllable phase slopes using reconfigurable transmission line configuration. Wideband frequency-dependent phase bits of 0 degrees, +/- 90 degrees, +/- 120 degrees, +/- 180 degrees, +/- 240 degrees, and +/- 270 degrees phase differences are achieved for a frequency band from 3.4 GHz to 3.7 GHz. A wideband planar antenna element with a dual-finger monopole and an 8-way wideband matched feedline are applied to the proposed system. From the experimental results, the frequency-selective beamforming array presents simultaneous channel-selective beams with steering angles of up to about +/- 40 degrees. The adjustable beamforming system can achieve inter-beam hand-off for 5G mobile applications.