Design and Synthesis of Chained-Response Multiband Filters

Given how important multiband filters are in the current era, little work seems to have come up with methods that can produce multiband filters of more than two passbands with flexibility in inner-band frequency selection, as well as specific bandwidths for each passband. In this paper, a novel method called the chained-response method is proposed. This method can produce multiband filters with the flexibility to specify accurately the bandwidths for each passband as well as its inner-band frequency selection. This paper describes the design procedure for this method. In order to validate the design procedure, a symmetrical dual-passband filter with bandwidths of 0.2 GHz for both passbands is designed. In order to show the novelty of this method, which is the flexibility of inner-band frequency selection and the specific bandwidths, an asymmetrical dual-passband filter with bandwidths of 0.2 GHz and 0.4 GHz is designed. Both the symmetrical and asymmetrical dual-passband filters are fabricated with a waveguide structure and the measurement results for both show good agreement with the theoretical ones. Finally, the mathematical modelling for a symmetric triple-passband filter and a symmetric quad-passband filter are briefly discussed to show how the proposed method can be expanded for designing filters with more than two passbands.