Novel Design Method of Constant Bandwidth Tunable Filters Based on Circuit Theory

In recent years, with the increased demand for information traffic, wireless communication is performed in various frequency bands, and tunable filters capable of supporting different frequency bands are attracting attention. However, the conventional tunable filter has a problem that the bandwidth changes greatly when the center frequency is changed. In this research, the authors propose a novel design method based on the circuit theory of a tunable filter with a constant absolute bandwidth. Design of a tunable filter has become much easier because there is no need to perform EM analysis. The validity of the design method was confirmed by simulation and experiments.