Left-handed wire antennas over ground plane with wideband tuning

Abstract

Tunable left-handed (LH) wire antennas over a ground plane are presented in this paper. These antennas are small and have a wide tuning bandwidth and are matched to 50 ? within the operation range. Two kinds of antennas have been developed: the monopole antenna and the half-loop antenna over ground plane. In both cases, the antennas are designed, manufactured and measured at fixed frequencies as a first step. After that, a study to replace some LH components with variable capacitors has been carried out for each antenna. Tunability over a wide bandwidth has been achieved. Finally, some prototypes of both antennas have been manufactured and measured. The tunable LH monopole antenna has been measured showing a monopolar radiation pattern with a 28% tuning bandwidth (695-924 MHz). Its radiation efficiency takes values between 50% and 70% within all the tuning bandwidth and the maximum dimension varies only between 0.11?0 at 695 MHz and 0.15?0 at 924 MHz. The tunable LH half-loop antenna over a ground plane has a radiation pattern with maximum radiation orthogonal to the ground plane. It has a 1.64:1 measured tuning bandwidth properly matched to 50 ? (considering |s11| <; -10 dB). Its measured radiation efficiency is always above 54% within the working bandwidth.