Synthesis of the Double-Ladder Topology with Arbitrary Bandwidths and Dual-Band Response

In this work, a new mapping function is proposed to carry out the exact synthesis of the double-ladder configuration with arbitrary bandwidths. The synthesis of such topology is based on the extracted-pole method, therefore, the way the input phase of the filter is constructed is critical, that is the single to dual-band domain mapping. The phase must be exactly the same at the frequency of the two transmission zeros to be extracted. In previous works, this was restricted to dual-band filters with equal absolute bandwidth. In this paper, the method has been extended to arbitrary bandwidths. A synthesis example is shown which demonstrates the validity of the mapping function.