A Miniaturized Frequency-Tunable Varactor-Loaded Dual-Band Shorted Multi-Ring Microstrip Antenna Fed by an L-probe with a Thick Dielectric Substrate

Abstract

This paper presents a miniaturized frequency-tunable varactor-loaded dual-band shorted multi-ring microstrip antenna (MR-MSA) fed by an L-probe with a thick dielectric substrate. The frequency-tunable MR-MSA consists of multiple ring patch elements arranged concentrically and a feeding L-probe arranged on a dielectric substrate. Two varactor diodes are mounted on each ring patch and resonant frequencies of the ring patches can be controlled electronically by the DC bias voltages applied to the varactor diodes independently. In order to miniaturize the ring patches, a varactor-loaded shorted MR-MSA has been proposed. By using via holes added at the center of the ring patch, the patch area of the MR-MSA can be reduced by a quarter in comparison with the original one. In this paper, a miniaturized varactor-loaded frequency-tunable dual-band MR-MSA with a thick dielectric substrate is proposed. Measured gain of the prototype MR-MSA with a thick substrate of 3.6 mm thickness is improved by approximately 5 dB in comparison with that with a thin substrate although the fractional frequency-tunable ranges of the two bands are almost unchanged.