A Wideband Frequency-Tunable Dipole Antenna Based on Antiresonance Characteristics

Abstract

We propose a novel frequency-tunable dipole antenna using varactor diodes and shunt inductors, which provides a much wider frequency tuning bandwidth. First, based on the simple series connection of non-Foster elements, we have predicted required reactance ensuring good impedance matching over a wide target frequency tuning band. Next, we have devised parallel connection of the diodes and the inductors to generate antiresonance behavior, which is necessary to produce the required reactance throughout the target frequency band. However, the inductor connected in parallel with the varactor diode always made the diode short-circuited. To solve the problem, we have inserted a narrow longitudinal slit in each dipole arm, which can maintain not only necessary dc isolation but also required RF connection with the help of a dc blocking capacitor bridging the slit. All measured results show good agreement with simulated ones, which proves the validity of our proposal.