Electrically tunable integrated patch antenna with planar filter

An electrically tunable planar hairpin filter integrated with a microstrip patch antenna is proposed in this paper. The patch antenna is integrated as a resonator, contributing to a second-order filter. The integration is performed to eliminate 50-ohm transition losses and reduce the overall structure size. The antenna is magnetically coupled to the hairpin resonator and operates at a center frequency of 3.03 GHz with a fractional bandwidth of 2.38%. The gain of the patch antenna is 5.41 dBi. Electrical tuning ability is provided via four varactors with a filter response tuning range from 2.77 GHz to 3.19 GHz.