Compact Dual-Band and Dual-Circularly Polarized Stacked Antenna With Capacitive Feeding

In this letter, a novel wearable dual-band and dual-circularly polarized antenna is proposed. Initially, the study is dedicated to the construction of unidirectional radiation using the TM₀₁ mode of the square patch and the TM₁₁ mode of the circular patch. Then, the symmetric oblique angles are cut out of the bottom square patch to resonate the left-hand circular polarization (LHCP) at low frequency band and asymmetric slots are etched on the top circular patch to resonate the right-hand circular polarization (RHCP) at high frequency band. Additionally, the impedance matching is improved by utilizing a rectangular slot on the bottom patch, enabling the antenna to cover the entire 2.45 GHz ISM frequency band at low frequency band. Besides, stable performance of the antenna is obtained when setting on different parts of the human body. The calculated specific absorption rate (SAR) values at both 2.45 and 3.6 GHz are all far lower than the upper limit of IEEE C95.1-2005 and EN 50361-2001. These properties proved the proposed antenna is suitable for wearable systems.