Two filters intended for application in highly integrated transmitters and receivers utilized in millimeter-wave multiband communication systems were implemented: a lumped-element version with a 4.7% bandwidth, centered at 26.8 GHz, and a coupled-resonator version with a 8.5% bandwidth, centered at 30.6 GHz. The filter topologies are shown.
In the lumped-element version , the LC resonators were implemented as p-networks with series spiral inductors and shunt capacitors implemented with micromachined cantilever-type varactors. In the coupled distributed resonator version , the resonators were implemented by half-wavelength resonators terminated in varactor connected to ground. Thus, by varying the capacitance of the varactors, the effective electrical length of the resonators deviated from half-wavelength and tuning is affected.