A Dual-Band Tunable Ultra-Thin Cavity Antenna

A dual-band ultra-thin cavity antenna with a wide tuning range is designed and fabricated. The overall dimensions are 31 × 15 × 0.5 mm³. The proposed cavity antenna is realized by making two adjacent side walls of a rectangular dielectric-filled resonant cavity open as radiating ports. The achievable frequency ratio changes from 1.2 to 2.2 with different aspect ratios. With a varactor diode installed at the front open port, the dual frequency bands can be tuned over a wide range. When the applied reverse biasing voltage varies from 3 to 13 V, the realized |S₁₁| <; -6 dB impedance bandwidth is 420 MHz (12.5%) and 960 MHz (20.5%) for the low band and the high band, respectively. The designed antenna occupies no area on a circuit board, and a 0.5-mm-thin volume inside a device cover is enough for installation. The dual bands can be scaled to other desired bands within the frequency ratio range.