Contactless Varactor-Loaded Bandwidth-Enhanced Frequency-Reconfigurable Patch Antenna
Jian Zhou, Jing Cai, Jian‐Xin Chen
Abstract
A contactless varactor-loaded bandwidth-enhanced frequency-reconfigurable (FR) antenna (FRA) is proposed. On account of the different E-field distributions of the TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> modes, six shorting pins are introduced in the voltage zero of the E-field of the TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode to push up the TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode, which helps degenerate two modes to broaden the bandwidth. After that, a pair of frequency tuning lines with varactors attached to one end is partially inserted under the patch in a novel way to continuously tune the two modes simultaneously. The novel varactor-loading scheme obtains a trade-off between a high efficiency of larger than 50% and a frequency tuning range of 22.2% (2.04 GHz to 2.55 GHz). The measured bandwidth exceeds 7.5%, exhibiting a bandwidth enhancement characteristic, and the peak gain varies between 6 and 7.9 dBi over the entire band.