Design and experimental S -parameter validation of a compact slot-loaded 3.5 GHz patch antenna and four-port MIMO configuration for IoT and vehicular applications

Abstract

Abstract A compact slot-loaded microstrip patch antenna operating at 3.5 GHz is presented for IoT, and Vehicular Applications. The antenna is designed on a Rogers RO4003C substrate and fed by a 50 Ω microstrip line. Three horizontal slots are introduced in the radiating patch to improve impedance matching and enhance bandwidth without increasing the antenna size. Simulations carried out in CST Microwave Studio and Ansys HFSS show a −10 dB impedance bandwidth of 90 MHz (3.43–3.52 GHz), a peak gain of 5.7 dBi, and a radiation efficiency above 89.8%. The fabricated prototype confirms the simulated performance, exhibiting good agreement between measured and simulated S 11 responses. To further enhance channel capacity, a four-port multiple-input multiple-output (MIMO) configuration is developed using identical elements in a 2 × 2 arrangement. The proposed MIMO antenna achieves port isolation better than −25 dB, an envelope correlation coefficient (ECC) below 0.0008, and a diversity gain close to 10 dB, indicating excellent spatial diversity and low mutual coupling. In addition, the results indicate high diversity performance, with a total active reflection coefficient of −13.22 dB and a channel capacity loss of 0.29 bps Hz −1 . The results indicate that the proposed antenna design is suitable for deployment in fixed 5 G customer premises equipment gateways, IoT infrastructure nodes, and vehicular platforms.