Optimized microstrip filter with varactor-controlled tuning

A band-pass filter on the basis of irregular microstrip varactor-tuned resonators is studied. The amplitude of the tuning rises with growth of the impedance step between microstrip lines forming the resonator. Maximum of tuning takes place when the ratio of low-impedance part length to high-impedance part length reaches 1/2. Ability is demonstrated to design a filter with a constant absolute bandwidth on filter tuning.