A High-Power S-Band Filter (Correspondence)

This note describes the measured performance of a high-power S-band "waffleiron" filter. Techniques for designing varying-impedance corrugated waveguide filters in rectangular waveguide have been available for some time [1 ]. If propagation is restricted to the dominant TE₁₀ mode, these filters have wide well-matched pass bands and wide high-attenuation stop bands. Unfortunately, the filters may have spurious transmissions in the stop band when power is incident upon them in other modes, such as TE₂₀ or TE₃₀, if the guide wavelength of these modes at the stop band frequencies is equal to the guide wavelength of the TE₁₀ mode at the pass-band frequencies of the filter.