A Miniature Spiral Diversity Antenna System With High Overall Gain Coverage and Low SAR

A miniature spiral diversity antenna system operating at 1.85 GHz is proposed. Two 10 times 6.25 mm antennas were placed at two corners of a printed circuit board at a height of 7 mm from the ground plane. Each antenna achieves nearly 7% bandwidth within 6 dB return loss. The mutual coupling between the two antennas is less than 10 dB. The proposed diversity antenna scheme exhibits high overall gain performance in all three principal planes compared to a single antenna solution. Computed specific absorption rate (SAR) data against a specific anthropomorphic mannequin (SAM) phantom and a hand model show that the diversity antenna system induces low SAR compared to a single antenna.