From Antenna to Filter or from Filter to Antenna

This paper presents the two filtering antennas. One (type-A) is to design an antenna, which simultaneously realizes the filtering performance. The other one (type-B) is from a filter to design an antenna. The type-A filtering antenna obtained a high selectivity by etching slots on a single patch. The radiation nulls can be controlled individually. On the other hand, the high selectivity of type-B filtering antenna's boresight gain response was achieved by a novel coupling scheme, which induces additional coupling between source/load and non-adjacent resonators to construct cross-coupling paths. For demonstration, two filtering antennas are designed.