Study of 2-bit Antenna–Filter–Antenna Elements for Reconfigurable Millimeter-Wave Lens Arrays

This paper presents a new reconfigurable antenna-filter-antenna (AFA) element based on slot antennas and switchable resonators. This reconfigurable AFA can operate in four modes of operation as a three- or four-pole filter, and yields a 2-bit variable phase delay. As a result, the multimode AFA can be used as the building block of 2-bit adaptive lens arrays. This paper details design, modeling, and miniaturization of the reconfigurable AFA, and demonstrates its performance through preconfigured prototypes. The proposed AFA has a loss of 1.4-1.6 dB measured at 32 GHz in both three- and four-pole filter modes, and exhibits a frequency response that is almost insensitive to the angle of incidence. Several proof-of-concept fixed lens arrays have been also fabricated for output beams scanned to 0deg, 15deg, 30deg, 45deg, and 60deg in the E- and H-plane. The measurement results show that the output beam can be scanned to plusmn60deg in both principle planes, with a worst case sidelobe level of less than -11 dB and a scan loss that hardly exceeds the theoretical limit