Inhomogeneous stepped-impedance corrugated waveguide low pass filters

Previous work on homogeneous stepped-impedance corrugated filters has been extended to the general inhomogeneous structure, where the waveguide broad dimension is varied in addition to the narrow dimension. It is then possible to design waveguide lowpass filters with specified stopbands free of spurious mode propagation to give rejection levels as high as 100 dB. Additionally, control over the lower cut-off frequency and the ability to match down almost to this frequency facilitates the design of compact waveguide bandpass filters having very broad bandwidths.