A Compact Textile Penta-Band Wearable Antenna Using Multimode Patch and Multi-Resonant Feeding for Off-Body Communications

This letter presents a compact textile penta-band wearable antenna for off-body communications. To resolve the challenge of implementing multiband operation with consistent polarization within limited volume, the proposed antenna design combines the techniques of multimode resonant patch and multi-resonant feeding. The upper radiating patch integrates a modified U-slot for enabling tri-band multimode resonance, while the middle-layer T-shaped feeding structure is loaded with two shorting pins and a notched square ring thus contributing two additional resonant bands via mode splitting. The antenna achieves a measured fractional operating bandwidth of 2.0%, 5.9%, 5.3%, 3.1% and 2.0% at 1.13, 1.62, 2.06, 2.62 and 2.88 GHz with |S₁₁| < -10 dB, respectively. Far-field measurement results confirm identical polarization mode and stable broadside radiation patterns across all bands. On-body evaluations reveal that the specific absorption rate values are below 0.4 W/kg with the input power of 1 W, complying well with the safety limit. This antenna shall be very attractive for off-body communications.