Integration of Lowpass Filters in Bandpass Filters for Stopband Improvement

A novel waveguide E-plane filter with suppressed spurious responses up to almost twice the center frequency is proposed. Stopband improvement is achieved by integration of lowpass ridged waveguide filter in an E-plane bandpass filter. The fabrication process remains simple as for standard E-plane metal insert filters. A time efficient simulation tool for the proposed structure has been developed. Numerical and experimental results are presented to confirm the improvement and the accuracy of the developed tool