Design of a Multiband Antenna With Polarization Diversity for Smartwatch Applications

This article presents a novel multiband polarization diversity watch antenna designed for smartwatch applications. The proposed antenna adopts the loop multimode resonant technology and the odd-even mode feeding technology. By exciting the first three modes of the loop of the watch frame, the effective resonance at 2.5, 4.4, and 5.8 GHz is achieved. The polarization diversity technology on the common aperture is realized through the odd-even mode feeding technology. Therefore, the orthogonal current directions are generated within the watch frame, and the watch strap is efficiently used for the diversity at 0.82 GHz, for n5, n41, n79, and industrial, scientific, and medical (ISM) band applications. Simulations and measurements from the watch antenna showed excellent performance in terms of reflection, far field, and polarization diversity. Besides that, additional evaluation on the human wrist also indicates low specific absorption ratio (SAR) and envelope correlation coefficient (ECC) levels. To the best of our knowledge, such multiband diversity antennas with favorable characteristics designed for watches are not evident in other state-of-the-art literature.