A Microstrip two-state switchable dual-band bandpass filter

A new two-state switchable dual-band bandpass filter (BPF) has been proposed. The BPF consists of a dual-band split-type filter and a dual-band stub-loaded resonator filter with a pair of controllable switching circuits. By controlling p-i-n diodes, two switchable on-state frequency responses can be realized. One state of the dual-band BPF provides a close band spacing, whereas the other state provides a wide band spacing. The two states can be switched independently. Actual circuit implementation was carried out to demonstrate the design idea, and the simulated results agree well with the measured results. Frequency ratios of 1.17 and 2.55 were achieved for the states I and II, respectively.