Bandwidth and frequency agile MIMO antenna for cognitive vehicular communications

A reconfigurable MIMO antenna for heterogeneous vehicular networks is reported in this paper. The frequency and bandwidth characteristics of the MIMO antenna can be reconfigured to meet multi-standard and multi-frequency requirements in automobiles. The antenna element evolved from an edge-chamfered ultra-wideband (UWB) antenna operating from 2.1 to >15 GHz. The bandwidth reconfiguration is achieved through the selection of excitation paths connecting the feed and radiator. The feedline selection is performed using PIN diodes, making the antenna operate in three distinct modes, namely, UWB mode (Mode 1: 2.1–>15 GHz), industrial, scientific and medical/Internet of Things (ISM/IoT) mode (Mode 2: 2.45 GHz), and wireless local area network (WLAN) mode (Mode 3: 5–6 GHz). The feed path corresponding to Mode 2 and Mode 3 is incorporated with a suitable filtering network to shape the frequency response of the antenna based on the user's requirements. Owing to the requirement of cognitive selection of frequency bands, the frequency tunability in Mode 2 is realized using varactor diodes. The varactor-incorporated feed path reconfigures the center frequency between 2.45 and 3.5 GHz. The proposed MIMO antenna offers gain and total efficiency greater than 2.94 dBi and 76%, respectively. The prototype of the 4-port MIMO antenna is being fabricated to test its functionality in real time.