A Differentially Fed Dual-Broadband End-Fire Filtering Antenna Without Extra Filtering Circuits for 5G IoT Applications

A novel dual-broadband end-fire filtering antenna for fifth-generation (5G) Internet of Things (IoT) applications, derived from the traditional single-layer Vivaldi antenna, is proposed. It employs a differential feedline to enable seamless integration with widely applied differential systems. First, by strategically designing the length of the feedline, an interband radiation null is generated, and its second-order radiation null is located at the upper stopband of the higher band (HB), thus achieving a dual-band operation with a certain filtering capability. Second, leveraging the property of these slots on the antenna’s tapered aperture position can be equivalent to the serial shorted branches with band-stop characteristics, the suppression effects within the interband and the upper stopband of the HB are enhanced by loading slots with different lengths. Finally, a pair of half-wavelength shorted stubs are loaded on the feedline to generate an extra radiation null, further strengthening the suppression level of the HB’s upper stopband and optimizing the overall impedance matching of the antenna. The designed prototype was fabricated and measured, validating that it has the –10 dB impedance fractional bandwidth of 73.3% and 34.3%, peak realized gains of 10.0 dBi and 10.0 dBi, and exhibits good out-of-band suppression performance without employing extra filtering circuits.