Synthesis and design of filtering antenna based on j/k inverters and ŀ/4 resonators

A compact filtering antenna based on alternative J/K inverters and λ/4 resonators are synthesized and designed in this paper. Parallel coupled line sections, via-holes, as well as L-shape monopole antenna are integrated to be a filtering antenna, with the parallel coupled line sections as J inverters and via-holes as K inverters. The L-shape monopole antenna is considered as a radiating impedance, and its equivalent circuit is first extract to replace the last resonator of the bandpass filter for the size reduction. The impedance matching of the antenna can be achieved by adjusting the last inverter of the filtering antenna and no extra impedance matching network is needed here. Finally, a filtering antenna operating at 2.4 GHz is designed and fabricated. Both the simulated and the measured results show a good frequency selectivity as a bandpass filter, and high radiation efficiency in the operating band as an antenna.