A Transparent Dielectric-Loaded Reconfigurable Antenna With a Wide Tuning Range

In this letter, a compact, frequency-reconfigurable antenna with a wide tuning range is proposed. It consists of a folded monopole structure, a transparent dielectric loading, and a varactor diode. The use of a water layer and a holder as the transparent dielectric loading can effectively reduce the antenna size, while keeping the antenna with a reasonable bandwidth and high efficiency. This new antenna occupies a compact volume of
$17 \times 14 \times 4\ \hbox{mm}^{3}$
(
$0.0237 {\lambda } \times 0.0196{\lambda } \times 0.006{\lambda }$
at 419 MHz). By controlling the dc voltage over the varactor diode, the operating frequency of the antenna can be continuously tuned from 419 to 883 MHz, which is a very wide tuning band for an electrically small antenna. Both the computer simulation and measurement are conducted. The results demonstrate that it is a very promising candidate for hand-portable devices.