Differentially Fed, Low-Profile, and Compact Patch Antenna for Millimeter-Wave Applications

This letter presents a novel differentially fed, low-profile, and compact patch antenna for millimeter-wave (MMW) applications. The antenna is constructed on a single-layer radiating structure and employs a central metal strip that is coplanar coupled to a pair of dual-patch resonators. This configuration excites multiple adjacent characteristic modes. By employing differential feeding, the two desired modes are selectively combined while unwanted modes are suppressed, thereby achieving wideband operation within an electrically thin profile. Characteristic Mode Analysis (CMA) is utilized to elucidate the working mechanism and guide the design. For demonstration, a prototype operating at 26 GHz is fabricated and measured, which has a size of 0.43λ0× 0.42λ0(λ0is the operating wavelength at 26 GHz in free space). Measurements show a 10-dB impedance matching bandwidth of 13.2%, a stable boresight gain of approximately 7.1 dBi, and a low profile of only 0.044λ0.