A Compact Filtering Patch Antenna With High Suppression Level and Its CP Application

In this letter, a novel compact filtering patch antenna with high suppression level is proposed. The fork-shaped feedline and the two half-wavelength strips are used to excite the antenna through magnetic coupling. Due to the quarter-wavelength branch of the feedline, a null below the operation band is introduced. Besides, owing to the introduced two strips, the multipath cancellation will occur at the patch and therefore generate a radiation null above the operation band. Based on the linearly polarized filtering antenna, a circularly polarized two-element filtering array with a wide 3 dB-AR bandwidth is also proposed. Both two works are analyzed, fabricated, and measured. Good agreement is achieved between the simulated and measured results. The proposed linearly polarized filtering patch antenna has a compact size of 0.378 λ
₀
× 0.378 λ
₀
× 0.035 λ
₀
, a peak gain of 8.26 dBi, and a frequency suppression level higher than 24.11 dB. The circularly polarized filtering array shows an impedance bandwidth of 11.4% and a wide 3 dB-ARBW totally covering the operation band.