Dual-Band Filtering Antenna With Novel Transmission Zero Characteristics

A single-layer two-pole dual-band filtering antenna (DBFA) with orthogonal polarizations in the two bands is presented in this letter. The DBFA is based on a common dual-mode T-shaped resonator (TR). The two modes of the common resonator each couple to one of the two orthogonally placed patches, resulting in required radiation. The TR is responsible for generation of three transmission zeroes (TZs) in frequency response corresponding to each polarization at the broadside: two of them being intrinsic TZs due to the TR and the third caused by far field interference of TR's radiation with that of the patch.The low profile microwave design has its two passbands operating at 4.13 and 4.7 GHz (resulting in a frequency ratio of 1.14) with 10 dB return loss bandwidths of 1.2% and 2.9%, respectively.