Compact Asymmetric-Slit Aperture Coupled Square Patch Antenna for V2X Communications

This paper presents the development of a compact asymmetric-slit aperture coupled square patch antenna designed for Vehicle-to-Everything (V2X) communications to operate at the center frequency of 3.5 GHz. The antenna employs an aperture-coupled feeding technique, where energy is transferred from the microstrip feeding line on the bottom layer through a coupling slot to excite the radiating square patch on the top layer. The structure is implemented using a twolayer FR4-epoxy substrate configuration, mechanically fastened with plastic screws. An asymmetric slit is introduced upon the radiating square patch to improve the impedance matching and to control the radiation performance. A reference antenna without using an asymmetric-slit is also designed with the same feeding technique for comparison. Simulation and measurement results demonstrate good agreement one each other, whereby the measurement achieves the reflection coefficient (S₁₁) value of -28.84 dB, the peak gain of 0.54 dBi, and the radiation pattern similar to a common microstrip patch antenna. Although the asymmetric-slit antenna exhibits a relatively modest peak gain, however, it is still within acceptable limits for general V2X communications, which emphasize omnidirectional coverage and stable radiation patterns over high-gain requirements.