Various multiple-input multiple-output (MIMO) antenna systems for automotive applications are presented in this paper using two uniquely designed elements: 1) a low profile wideband Planar Inverted-F antenna (PIFA), and 2) a compact wideband monopole in the sub-6 GHz 5G systems and Vehicle-to-Everything (V2X) communications that cover the frequency range from 617 MHz to 6 GHz. The proposed MIMO systems can be used in a low-profile or shark fin style housing placed on the vehicle's roof. Each MIMO system achieves satisfactory performance across the whole band with suitable physical dimensions. The envelope correlation coefficient (ECC) and diversity gain (DG) are calculated using MATLAB in each MIMO configuration as they represent the two key factors in the MIMO performance. Simulation results are presented along with measured data on a 1-meter rollededge ground plane (GND) and on a vehicle's roof from properly cut metal sheet prototypes. The results are discussed in terms of VSWR, passive isolation between elements, combined radiation patterns, port-efficiencies, ECC, and DG.

This paper introduces a low profile wideband Planar Inverted-F antenna (PIFA) for vehicular applications in the 5G systems (below 6 GHz) and Vehicle-to-Everything (V2X) communications. The antenna covers a wide range of bandwidth which operates from 617 MHz to 6 GHz while having an acceptable filtering on the GNSS bands. This design's physical dimensions and electrical performance make it suitable for low profile wireless applications in the automotive field. Measurement data on Ground plane (GND) and on vehicle are presented from a properly cut metal sheet prototype along with simulated results of the model design. Simulation and measurement results are discussed in terms of VSWR, surface current distribution, radiation patterns, antenna efficiency, and linear average gain (LAG).