A straight-line equation for the notch tailoring of a microwave extra wideband filter

This paper deals with a flexible CAD methodology for the design of a microwave extra wideband filter introducing a notch at a desired frequency. The structure, designed in a cost-effective planar microstrip technology to operate in the 5–20 GHz frequency band, is capable of covering up to 120% of fractional bandwidth. It shows good performance in terms of in-band and out-of-band insertion loss and group delay. Furthermore, a simple relationship between the notch frequency and a single geometrical parameter of the structure has been extracted, thus making the component highly flexible to design. The procedure steps and the relevant design results are reported, including the electromagnetic analysis of the port connectors. Finally, different samples of the filter have been realized and measured to test the procedure. The experimental results have shown a good agreement with the expected performance thus confirming the effectiveness of the proposed methodology.