A Compact Low-Profile Differential Dual-Polarized Filtenna Without an External Filter Circuit for Vehicular Communications

A compact low-profile differential dual-polarized filtenna without an external filter circuit for vehicular communications is proposed in this paper. It has a compact, low-profile, simple, and symmetrical structure, which consists of four identical quarter circular patches with a pair of crossed feeding lines symmetrically and orthogonally embedded. Good filtering performance with three radiation nulls (RNs) generated without extra filtering structure is achieved, and the production mechanisms of three RNs are studied numerically. To get a deep insight into its working mechanism, the proposed structure is analyzed, and the equivalent lumped circuit is modeled and simulated. The prototype antenna with low profile of 2.832 mm and average gain of about 9.1 dBi within the frequency band of 5.28-6.11 GHz is fabricated and measured. Moreover, the measured polarization isolation is more than 44 dB within the operating band and the measured cross-polarization level is less than -29 dB. Good agreement between simulated and measured results can be acquired. The proposed antenna is a good candidate for in-vehicle local area networks (WLAN), in-vehicle Wi-Fi 6E, vehicle-to-vehicle (V2V) communication and 5G vehicle-to-basestation communication applications.