dA compact dual-band tunable filter adopting cross coupling structure

A compact dual-band tunable bandpass filter operating in the range of 330MHz to 400MHz was proposed in this letter. The dual-band tunable bandpass filter was consisted of four rectangular ring tunable resonators and a cross type coupling structure. The cross type coupling structure also played the roles of a resonator. The desired performance of a dual-band tunable filter can be designed easily using the cross type coupling structure. The performance of the two passband can be adjusted dependently and has little influence to each other. The size of this tunable filter was less than 0.16λ*0.14λ normalized to 400MHz.