A Compact Wide-Range Frequency and Bandwidth Reconfigurable Filter

This letter proposes a wide-range reconfigurable bandpass filter (WRBPF) based on the cross-shape triple-mode resonator. Varactor diodes and switching diodes are utilized at the ends of the resonator and the positions of external coupling, which combines the two working modes of the low-frequency band and high-frequency band, greatly broaden the tunable range of the center frequency (ƒ₀). When the 3-dB bandwidth of WRBPF is 180 MHz, ƒ₀ can be adjusted from 0.78 to 1.93 GHz, and the relative adjustment range is 84.9%. When ƒ₀ is 1.355 GHz, the absolute bandwidth can be adjusted from 110 to 950 MHz, and the relative bandwidth adjustment range is 8.1%–70.1%. Moreover, the circuit size of WRBPF is only 0.29 λg × 0.22 λg. The experimental results show that WRBPF has not only a simple structure but also an excellent performance.