A Circularly Polarized Switched Beam Antenna with Pattern Diversity for WiFi Applications

This letter presents a switched beam antenna optimized for operation at 2.45 GHz. The antenna is composed of two disc-based patches arranged in a concentric single-layer structure. The beamset is composed of one directive broadside pattern, two symmetrical tilted directive patterns, and one conical pattern. The beams are circularly polarized and only moderately correlated, making the device suitable for space diversity medium access for IEEE 802.11 communication in complex areas. Experimental validations confirm a cumulative pattern with a maximum gain of 2.8 dB, covering the half-plane with only 7 dB of ripple. An axial ratio below 3 dB for the entire beam-set and correlation coefficients as low as 0.17 are also observed at center frequency. The moderate beam correlation for the WiFi band confirms the effectiveness of the device.