A tunable ferrimagnetic resonator circuit includes a fixed magnetic polepiece, a rotatable magnetic polepiece spaced from the fixed polepiece, an electromagnet for varying a magnetic field between the fixed and rotatable polepieces and a plurality of ferrimagnetic resonators connected in series and located in the magnetic field between the fixed and rotatable polepieces. The ferrimagnetic resonators include an initial resonator having an input port, a final resonator having an output port and one or more intermediate resonators. The rotatable polepiece preferably has a poleface having a first surface region that causes a constant magnetic field to be applied to the intermediate resonators as the polepiece is rotated, and second and third surface regions that cause variable magnetic fields to be applied to the initial and final resonators, respectively, as the polepiece is rotated. The polepiece is rotated to a position where each of the resonators is tuned to substantially the same resonance frequency.