Design and Testing of a Thermally Stable Filter Using Bimetal Compensation

In this paper, it is proposed that a variable length bimetal tuning screw can be used to compensate for temperature drift in waveguide resonators and filters constructed from high CTE materials such as aluminum. A method is proposed for designing and tuning a bimetal tuning screw. A method is also proposed for applying this approach to filter compensation. Experimental results are provided for a compensated aluminum cavity, and filter. Temperature drift in the resonator is reduced to -0.382 ppm/degC from -23 ppm/degC. Experimental results are provided for a narrow-band inductive-iris Chebyshev band-pass filter demonstrating a reduction in temperature drift from -23 ppm/degC to 2.35 ppm/degC.