Dual-Mode Patch Antenna With Capacitive Coupling Structure for On-/Off-Body Applications

A dual-band dual-mode antenna for on-/off-body centric communications is proposed for 2.4 and 5.8 GHz industrial scientific medical bands. Using polydimethylsiloxane as substrate, the proposed antenna has a compact structure and is easy to wear. The on-body mode is realized by a circular patch loaded with four symmetrically distributed metallic vias to generate TM$_{\mathbf{01}}$ mode located on the lower substrate. The off-body mode is achieved by a smaller circular patch on the top of the upper substrate, which generates a directional radiation pattern by exciting its TM$_{\mathbf{11}}$ mode. The measured operating bandwidths of the proposed antenna in two bands are 90 MHz (2.40-2.49 GHz) and 330 MHz (5.63-5.96 GHz), respectively. Average gain for the on-body mode is $-$2.38 dBi and for the off-body mode is 6.67 dBi. In addition, the antenna exhibits a robust performance near human tissue and low specific absorption rate values.