YIG-tuned circuit with rotatable magnetic polepiece

A tunable ferrimagnetic resonator circuit comprising:

• a fixed magnetic polepiece;
• a rotatable magnetic polepiece spaced from said fixed polepiece;
• an electromagnet for producing a magnetic field between said fixed and rotatable polepieces;
• and
• a plurality of ferrimagnetic resonators connected in series and located in the magnetic field between said fixed and rotatable polepieces, including an initial resonator having an input port, a final resonator having an output port and one or more intermediate resonators, for receiving an RF signal at the input port and coupling the input signal to the output port when the frequency of the RF input signal is substantially the same as the resonance frequency produced in the ferrimagnetic resonators by the magnetic field, said rotatable polepiece having a poleface including a first surface region adjacent to said one or more intermediate resonators, a second surface region adjacent to said initial resonator, and a third surface region adjacent to said final resonator, said first surface region being substantially flat and lying in a plane perpendicular to said magnetic field, said second and third surface regions being inclined with respect to said magnetic field so that when said polepiece is rotated about an axis parallel to said magnetic field, a constant magnetic field is applied to said one or more intermediate resonators and variable magnetic fields are applied to said initial and final resonators.