Broadband Pattern-Reconfigurable Filtering Microstrip Antenna With Quasi-Yagi Structure

In this letter, a compact pattern-reconfigurable filtering microstrip antenna is presented with broad bandwidth, good selectivity at the passband edge, and flat gain-frequency response. The pattern-reconfigurable filtering antenna has four resonant modes that can be adjusted independently: Three of them are created by multimode resonator (MMR), and the other one is by radiator. The four resonant modes are well distributed in desired band, and the resonant mode of radiator is located between the first two resonant modes of MMR. By the incorporation of two p-i-n diodes and metal strips, the radiation patterns can be reconfigured. When the resonant mode of radiator shifts slightly, the bandwidth and in-band characteristic of the filtering antenna are basically unaffected. Finally, a pattern-reconfigurable filtering antenna prototype with a fractional bandwidth of 25% at 5.2 GHz is designed and manufactured. The measured results are well-followed designed ones.