Synthesis method of lumped dualband filters with controllable bandwidths
This article presents a synthesis method for lumped dual-band filters by directly adopting traditional Pi-shaped and ?-shaped capacitive networks as dual-mode admittance inverters (J inverters). By following classic coupled-resonator filter theory, the equivalent circuits (parallel LCs) of the dual-mode resonators between the J inverters are derived separately at the two passbands. Each dual-mode resonator is first approximately constructed with a series combination of the two parallel lumped circuit (LC) resonators, and then the element values are iteratively updated for better accuracy. A design example is given and good agreement is achieved between the simulated and measured results, demonstrating the feasibility of the synthesis method. The passband bandwidths are fully controllable.  2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:7580, 2015.
controllable bandwidths lumped dual-band filter dual-mode j inverter