A Dual-Beam Wideband Filtering Patch Antenna with Absorptive Band-edge Radiation Nulls

A dual-beam filtering patch antenna with two absorptive band-edge radiation nulls and four reflective stopband radiation nulls is proposed. By loading a pair of T-shaped metallic strip underneath the radiating patch, a modified TM22 mode with TM20-like radiation pattern is obtained, which combines with the TM20 mode of the radiating patch, generating a wide operating band with symmetrical dual-beam radiation pattern. Two reflective radiation nulls are generated in both upper and lower stopbands for suppressing the out-of-band radiation. Through embedding two pairs of shorted small patch in the radiating patch, one absorptive radiation null combining with one absorptive resonant mode is produced at each band edge to absorb the band-edge incident energy, leading to a reduced reflection and sharp roll-off at both band edges, and therefore, the transceiver can be protected. With a total height of 0.038 λ0, a prototype is designed, fabricated and measured, showing a -10 dB impedance bandwidth from 4.63 to 6.10 GHz with sharp band-edge roll-off, two radiation beams directed at ± 40° with an in-band gain of 6.0 dBi, and a high out-of-band suppression of over 15 dB.