Abstract-A reconfigurable stacked microstrip patch antenna is proposed. The antenna operates at an upper frequency f u with a broadside pattern, 7.5-dBi right-hand circularly polarized gain, and 15.8% bandwidth. At a lower frequency f l , the antenna operates as a planar inverted-F antenna (7.3% bandwidth and 3.9-dBi peak gain) with the main beam directed close to the horizon. Switching between the two regimes of operation is achieved using p-i-n diodes. Antenna operation in the upper frequency band is suitable for low-earth-orbit or medium-earth-orbit satellite communications, and in the lower frequency band, the antenna is useful for terrestrial land-mobile or other wireless applications.Index Terms-Reconfigurable antenna, satellite link, stacked patch antenna, terrestrial link.

Abstract-The resonant frequencies and input impedance of a microstrip-fed third order Hilbert slot antenna are studied as function of antenna and substrate parameters. A distinct dualband characteristic is observed. Findings from HFSS simulation are validated by prototype fabrication and experimental measurement. The two resonant frequencies maintain a ratio of approximately 1.4 for narrow slots. A design parameter, L ax is identified which needs to be about 0.80λ g at the lowest operating frequency. The Hilbert slot provides a unidirectional pattern when operated against a metallic ground plane while maintaining dual-band characteristics.

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Abstract-A miniature spiral diversity antenna system operating at 1.85 GHz is proposed. Two 10 mm 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.

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