Passband miniature filter using short-circuit hybrid resonators

The paper presents a new concept of bandpass filters based on ½ wavelength resonators short-circuited and loaded at their middle by a series capacitor. The advantage of this type of resonator is the compactness and the possibility of achieving tunable filters. Simulation results for a hybrid technology (PCB-Surface Mount Components) to validate the concept show that miniaturization can reach a factor of 4. Thus, resonators with lengths λ_g/8 (to obtain miniaturization percentage of 75%) can be used instead of λ_g/2 when designing filters. We also show the possibility of making the miniature filters tunable through a series of simulations.