C-band microstrip based bandpass filter with design oriented transmission zeros allocation

This paper presents microstrip band pass filter design which is orientated towards positioning of transmission zeros at particular frequencies as a design goal. This flexibility of choosing these transmission zeros helps in suppressing unwanted spurious or intermodulation components which otherwise requires higher order sharp skirt filter to achieve the stop-band rejection. If there are limited number of such spurious components, and a high rejection rate is required, this filter provides better design choice in terms of size and rejection level, rather using a conventional polynomial based cross-coupled filters. The design methodology is validated with a design of 4.5 GHz bandpass filter of 20 MHz bandwidth with attenuation zeros placed at ±500 MHz from the center frequency.