(英) |
This paper presents various designs of frequency-tunable microstrip antennas fed by an L-probe with varactor diodes. In order to develop a frequency-tunable multiband planar antenna, ring microstrip antennas with two varactor diodes mounted on each ring patch are arranged concentrically on a dielectric substrate. An L-shaped feeding probe arranged under the ring patches or in the same layer as the ring patches is used to excite them. Resonant frequency of each ring patch can be controlled by a DC bias voltage applied the varactor diodes. In this paper, basic operation and performance of the proposed frequency-tunable microstrip antennas with a double-layer and single-layer dielectric substrate are demonstrated. |