Design of 5-order Interdigital Band-Pass Filter

This study proposed an interdigital band-pass filter based on the microstrip transmission line.When designing a conventional structure for an interdigital filter based on the characteristics of the 5th order transmission line, seven resonators are required.By changing the impedance of the resonator adjacent to the feed line, the proposed interdigital band-pass filter was designed to reduce the number of resonators compared to conventional interdigital band-pass filters.Consequently, the resonator order decreased, and return and insertion losses become comparable to that in case of a conventional interdigital filter design.The proposed band-pass filter was designed with a center frequency of 2.75 GHz and a bandwidth of 1.5 GHz.Furthermore, based on various transmission characteristics such as group delay and coupling coefficient, two band-pass filters were designed, compared, and analyzed.