Textile Pattern-Reconfigurable Antennas for 2.45 GHz Off-Body and On-Body Communications

Electrical radiation pattern reconfiguration for textile antennas using diode-based bias circuits is challenging, as most textile materials cannot withstand high soldering temperatures. Metallic snap buttons, widely used in garment manufacturing, can be readily integrated into textile antennas as mechanical pattern-reconfiguration switches. Accordingly, four sets of copper snap buttons are loaded on a square microstrip patch antenna (MPA). The antenna operates in fundamental patch and monopole modes under OFF and ON states, respectively, which yields distinct resonant frequencies for the two reconfigurable modes. Analysis of the simulated currents on the patch inspires two strategies to align both the patch-mode and monopole-mode resonant frequencies at 2.45 GHz. The first employs two parallel slots between the feeding probe and snap buttons to extend the monopole-mode current path while maintaining the patch-mode current path unchanged. The second increases the patch width to achieve similar current-path tuning. Two textile antennas are designed and fabricated following the two strategies. Simulations and prototype measurements validate the 2.45 GHz pattern reconfiguration of the two designs and further verify their robustness against human-body loading and bending deformation.