Coupling matrix synthesis of triple-passband filters using optimisation

In this paper a coupling matrix synthesis procedure based on a combination of global and local optimisations has been presented. The coupling matrices of two high-order triple-band filters have been synthesized to demonstrate its applicability for cross-coupled filters with complex topologies and frequency responses. Convergence of the optimisation is fast and no initial values for control parameters are required. This technique can be used to synthesize many other multiple-passband filters. These coupling matrices can be used to produce practical filters with any resonator.