Dual-band MNG patch antenna for smart helmet

A novel dual-band compact patch wireless fidelity (Wi-Fi) antenna using mu-negative (MNG) transmission lines (TLs) for the smart helmet is presented. In the smart helmet scenario, rescue agent is able to communicate with the other rescue agents, control centre, and drones via the helmet by Wi-Fi dual bands. For the smart helmet communication, the antenna, which consists of two MNG-TL loops located on the outside and inside, is devised. The dual-band corresponds to the zeroth-order resonance (ZOR) and second-positive-order resonance (SPOR) of the outer MNG-TL. The ZOR frequency of the outer MNG-TL is near the Wi-Fi 2.4 GHz band, and the SPOR frequency of the outer MNG-TL, excited by the coupling between the inner and outer MNG-TL loops, is the Wi-Fi 5 GHz band. The prototype of the proposed antenna has been fabricated and measured. The bandwidth of the antenna includes Wi-Fi 2.4 and 5 GHz bands with high radiation efficiencies of > 49% and a compact size of 27.6 mm x 27.6 mm x 1.27 mm (1/4.5 lambda x 1/4.5 lambda x 1/98.4 lambda at the lowest operating frequency).