A Compact Single-Layer Q-Band Tapered Slot Antenna Array With Phase-Shifting Inductive Windows for Endfire Patterns

A wideband millimeter-wave (mmW) tapered slot antenna (TSA) array operating in the Q-band is reported, aiming at the upcoming fifth-generation wireless communications. The antenna element is comprised by a TSA with two arrays of comb-shaped slits symmetrically cut on the edges of the two fins, respectively, which enables a degree of miniaturization for the radiator. Importantly, the geometrical structures of adjacent elements are flipped such that the fins of two neighboring TSAs are electrically connected. A miniaturized T-shaped eight-way power divider based on substrate integrated waveguide (SIW) technology is used to feed the linear array, where adjacent output channels are out-of-phase. In order to compensate the phase errors caused by the conventional compact T-shaped eight-way power divider, a well-tuned matching circuit composed of two consecutive inductive windows embedded inside the SIW is employed behind each TSA element, resulting in an enhanced gain and a low sidelobe level over a wide bandwidth. A prototype of the proposed antenna is fabricated using standard printed circuit board process and characterized, showing a good agreement between measured results and simulation predictions. The fabricated antenna experimentally achieves an $S_{11} < -10$ dB bandwidth of 13.0% (38.97–44.45 GHz), within which the gain is higher than 13.4 dBi and the sidelobe level is below −14.6 dB. Its directive endfire radiation patterns and wideband operation make it a suitable candidate for various mmW wireless communication systems.