A miniaturized tunable bandpass filter using asymmetric coupled lines and varactors

Nowadays, it becomes more and more important to miniaturize bandpass filters(BPFs) in RF front-ends because of size requirement of communication systems. As to achieve multifunction of RF front-end, BPFs with tunable passband, on the other hand, is another popular direction of BPF design. In this paper, a new three-order chebyshev BPF using asymmetry coupled lines and varactors, whose passband is widely tunable while the size is extremely reduced at the same time, is presented. Measurement results show that the center frequency of the proposed BPF has an amazing large tuning range from about 521MHz to 1123MHz for different bias voltage of varactors.