Design of Compact Dual-Band Eighth-Mode SIW Antenna for On-Body ISM Band Application

In this work, a dual-band, compact, eight-mode substrate-integrated waveguide (EMSIW) antenna is presented for 2.4 GHz and 5.8 GHz Wireless Body Area Networks (WBANs) applications. The electrical size of the proposed antenna is reduced by 1/8th compared to a conventional rectangular SIW cavity resonator by using the EMSIW approach. With the eight-mode concept, the dominant mode is preserved at the same frequency while achieving a large reduction in antenna size. The dominant mode’s resonance frequency is independently adjusted to 2.4 GHz, and a higher-order mode operates at 5.8 GHz. When both slots are loaded in an EMSIW, the radiation pattern at 5.8 GHz is enhanced in the broadside direction.The antenna’s on-body performance is validated using a biological phantom model at 2.4 GHz and 5.8 GHz, demonstrating lower sensitivity. The antenna’s simulated efficiency and measured gain in free space are 5.9 dBi and 60% and 3.8 dBi and 60%, respectively. The simulated Specific Absorption Rate (SAR) values are within acceptable limits for on-body WBAN applications, attributed to the predominantly unidirectional radiation from the antenna resulting in low SAR values. Additionally, the measurement results align well with the simulation outcomes.