Endfire Coupled-Mode Patch Antenna Array with Balanced Feeding

A two-endfire-element array with balanced feeding structure is proposed in this paper. The array contains two endfire coupled-mode patch antennas (CMPA) [1], which are fed by a T-shape parallel plate waveguide (PPWG) power divider. The PPWG feeding provides well-balanced input signal while maintaining low profile. It eliminates the undesired radiation of common-mode current, and thus addresses the major issue for the endfire CMPA. The performance of the single antenna fed by PPWG is analyzed and compared with the same antenna fed by microstrip line (MSL). The proposed array has measured bandwidth of 2.1% centered at 2.435 GHz. It offers 4.6 dBi peak gain at endfire and maximum front-to-back ratio of 23 dB. The proposed array radiates exact endfire patterns with vertical polarization while maintaining compact size and low profile.