A Dual-band PIFA Design Based on CMA for ISM Band Wearable Applications

In this paper, a dual-band wearable planar inverted - F antenna (PIFA) based on characteristic mode analysis (CMA) theory is proposed. The antenna can cover 0.43 GHz and 2.45 GHz Industrial Scientific Medical (ISM) bands. A slot and a defect structure are cut to adjust the resonances of the radiator. By adjusting the model significance (MS) values of the characteristic modes, the antenna can be optimized to achieve a good radiation performance without considering the feeding structure. The final antenna has a dimension with $0.18 \times 0.11 \times 0.008 \lambda^{3}$ (at 0.43 GHz), and the impedance matching band ranges from 0.417 GHz to 0.443 GHz, and from 2.20 GHz and 2.85 GHz. The maximum gain is -3 dBi and 4.3 dBi in the lower and upper bands, respectively. Meanwhile, Specific Absorption Rate (SAR) is evaluated in simulation, and the values are far lower than the recommended standards by FCC. Eventually, the prototype is fabricated and measured. The test results have the reasonable agreement with the simulation ones. The proposed antenna is an applicable candidate for wearable communication systems.