Reconfigurable Microstrip Yagi-Uda Antenna with a Scannable Circularly Polarized Beam

This paper proposes a novel reconfigurable microstrip antenna with circularly polarized beam scanning feature. It is based on a microstrip Yagi-Uda antenna of two square patches. One patch is driven with two orthogonal feeds and the other is a parasitic. The parasitic patch is loaded with four lumped varactors and a DC biasing network, to effectively change its electrical size. Because the main beam direction is determined by the electrical size of the parasitic patch, electronic beam scanning is allowed by changing the capacitance value through the applied DC voltage. Operating at 2.45 GHz, the antenna shows a beam scanning range from -36(sic) to 32(sic) with 2.3 dB gain variation across the entire scanning range and gain peak value of 8.1dBi.