A Tunable Combline Bandpass Filter Loaded With Series Resonator

摘要: This paper proposes a varactor-tuned microstrip combline bandpass filter (BPF) that is loaded with lumped series resonators instead of the short-circuited end combline. configuration has advantage enhancing tunability suggested BPF by varactor diodes in resonators, which leads to wide tuning range even small capacitance ratio (Cratio) varactor. Therefore, low controlled bias voltage can be achieved. In addition, due controllable slope parameter proposed resonator, coupling between controlled. As result, tunable keep nearly constant bandwidth over range. The insertion loss resulting from varactors compensated using an active circuit negative resistance. Theoretical analysis and design approach are described. Experimental results demonstrative show 500-MHz (1.7-2.2 GHz) Cratio only 2.6 (1-5-V voltage) while maintaining absolute loss. measured performance fabricated shows good agreement simulated one.