Design of dual band microwave filter by using interdigital technology

Abstract

This paper presents an analytical methodology for designing a dual passband filter, using frequency transformation between the normalized frequency domain and the actual frequency domain of the filter. The proposed methodology is purely analytical method in the process of finding the coupling matrix that fulfills the required filter specifications, without the need to perform numerical optimization of the coupling matrix in order to obtain the two-pass prototype domain response. The procedure also includes finding the equivalent circuit for this type of filters, which includes connecting each of the primary resonators of the filter with a resonator responsible for the stop band in order to obtain dual frequency resonance resonators. The frequency transformation is verified through an example. The derived equivalent circuit and coupling matrix are also analytically validated through the same example. Using electromagnetic structures simulation program, a dual bandpass interdigital filter is designed, the filter met the filter specifications for the example presented. The simulation results showed that the required specifications of the filter's frequency response could be achieved.