Filtering Antenna with High Selectivity Using Multiple Coupling Paths from Source/Load to Resonators

This paper presents a filtering antenna with high selectivity using multiple coupling path from source/load to resonators. The high selectivity of the filtering antenna’s boresight gain response is achieved by a novel coupling scheme, which induces additional coupling between source/load and non-adjacent resonators to construct cross-coupling paths. Thanks to the extra cross-coupling paths, the filtering antenna can generate maximum of N radiation nulls with N resonators. Besides, resonator using a combination of open-ended stub and short-ended stub is adopted to construct this novel coupling scheme more easily. For demonstration, a three-order filtering stacked patch antenna with a center frequency of 2.3 GHz and fractional bandwidth of 15.2% is fabricated. Two independently controllable radiation nulls are located at 1.97GHz and 2.61 GHz. Unidirectional radiation patterns have been achieved with cross-polarization lower than -20 dB and back lobes lower than -18 dB.