A Microstrip Filtering Patch Antenna with Asymmetric Gain Response

This paper presents a novel structure of a compact microstrip filtering patch antenna with asymmetric gain response. A rectangle patch antenna is excited by open-loop resonators through apertures in the co-grounded plane. This coupled patch not only produces three reflection zeros to increase the bandwidth of the antenna, but also generates a radiation null at one side of the band edge to improve selectivity. The design and simulation process follow the design method of a third-order cascade trisection (CT) bandpass filter. This integration approach eliminates the 50 Ohm interfaces between the cascaded filter and antenna while achieving an enhanced frequency selectivity. Measured results of the fabricated circuits show a good agreement with the simulation results.