Design and performance analysis of a PBG substrate MIMO antenna with RLC validation for 6G and IoT applications

A photonic band gap (PBG) substrate-based 1 × 2 multiple-input and multiple-output (MIMO) antenna is presented for terahertz (THz) 6 G and Internet of Things (IoT) applications. The proposed radiating element comprises a graphene patch and ground plane on a polyimide substrate, and a hybrid slot-elliptical PBG unit cell with a slotted decoupling wall is introduced to reduce the mutual coupling. It demonstrates four resonant frequencies (2.35, 3.6, 4.51, and 6.42 THz) covering two operation bands (1.477–2.67 THz, bandwidth (BW) = 1.19 THz and 3.35–7.08 THz, BW = 3.72 THz) with an excellent peak gain of 10.58 dB, radiation efficiency of 85.82%, envelope correlation coefficient (ECC) of 0.0004, diversity gain (DG) of 9.997 dB, and decoupling isolation of − 31.1 dB. The total active reflection coefficient (TARC) is maintained below − 10 dB over the operational band, ensuring a good impedance match for the two antenna ports excited simultaneously. The channel capacity loss (CCL) is below 0.45 bits/s/Hz, and the mean effective gain (MEG) difference between the two ports is within 3 dB, demonstrating the channel’s ability to maintain a consistent bit rate and uniform power transfer to both ports. An equivalent RLC circuit model developed in Agilent Advanced Design System (ADS) shows good agreement with the Computer Simulation Technology (CST) simulated S11 response, with a root-mean-square error (RMSE) of 3.37 dB and a mean absolute error (MAE) of 2.42 dB. The proposed MIMO antenna shows enhanced performance with a compact normalized area of 0.62 λ 0 × 1.74 λ 0 compared to the recently reported PBG and MIMO antennas in the literature.