Compact broadband slot-based MIMO antenna array for vehicular environment

This article presents the design, fabrication, and testing of a broadband directional slot antenna and its application in a vehicular environment. The proposed antenna consists of a slot antenna fed by a simple microstrip line. Broadband impedance matching is achieved by replacing the conventional microstrip line with a modified microstrip line. The modified microstrip line consists of a microstrip line terminated with an impedance transformer and a square patch. The proposed antenna offers 76.9% bandwidth centered around 4.8 GHz covering most of the communication applications between 3 and 6.75 GHz. Furthermore, the antenna's radiation pattern is shaped to obtain the desired directional characteristics using a simple reflector and array of via holes. The typical gain enhancement is 2.45 dBi at 5 GHz. This gain enhanced slot antenna is further used to construct the four-element MIMO antenna. The proposed MIMO antenna configuration offers omnidirectional coverage with realized antenna gain greater than 6 dBi making the antenna more suitable for the vehicular environment. The prototype antenna and the MIMO array are fabricated and measurement results are presented. The measurement results are in good agreement with the simulation results.