Waveguide bandpass filter of millimetre waves using polycrystalline yttrium iron garnet

The paper describes the properties of a TE₁₀ metal waveguide filter with a polycrystalline yttrium iron garnet at millimetre wave frequency, and compares theoretical and experimental results. A bandpass filter is formed by making a cut-off region in the original TE₁₀ metal waveguide: its characteristics are analysed using a mode-matching technique. It becomes clear that the insertion loss and the quality factor strongly depend on the thickness and the magnetic resonance linewidth ΔH of the material. A good magnetically tunable response is observed, with a quality factor of 250 and a few dBs insertion loss, and this agrees reasonably well with predicted values