Independently Tunable Low-Profile Dual-Band High-Impedance Surface Antenna System for Applications in UHF Band

An independently tunable low-profile dual-band high-impedance surface (HIS) antenna system is presented which employs a single layer cross bow-tie dual-band tunable HIS ground plane with a printed wideband monopole antenna designed to cover the UHF band. The unit cell of the proposed HIS ground plane is 19.71 mm by 19.71 mm with thickness of 1.74 mm. Simulations of the HIS ground plane have illustrated that either single or dual-band reconfigurable reflection phase resonances can be achieved between 0.95 GHz and 2.45 GHz by controlling C1 (4.55 pF~0.6 pF) and C2 (4.55 pF~0.6 pF) independently which represent the two groups of varactor diodes mounted on the surface elements of the HIS. Simulations with the wideband antenna 4 mm above the HIS ground plane illustrate an effective tunable operational bandwidth from 1.07 GHz to 2.75 GHz with a dual-band capability. Parametric studies indicate the radiation efficiency of the system increases as the antenna height is increased and the diode resistance is reduced. The radiation efficiency also increases with the frequency in general over the tunable frequency range and with the optimum parameters typical values from -4 dB to -2 dB can be achieved. The proposed HIS ground plane and the wideband antenna have been fabricated with Toshiba 1SV245 varactor diodes and it has shown an effective tunable bandwidth from 0.9 GHz to 2.8 GHz approximately with the dual band capability.