Structural passive synthesis of three-dimensional recursive cone filters

A simple analytical design method for structurally passive three-dimensional recursive cone filters is presented. The cone filter is realized by cascading two structurally passive two-dimensional recursive fan filters having different passband orientations. The orientation of the passband of the cone filter is easily obtained by simply choosing the proper orientations of the two two-dimensional fan filters. This design scheme is accomplished analytically without resorting to costly numerical optimization as previously reported. A design example is included.<>