Direct Synthesis of Parallel-Connected Symmetrical Two-Port Filters

This brief presents a general technique for the synthesis of parallel-connected two-port networks. This is based on the even- and odd-mode admittances of a standard Chebyshev network. The expressions for the even/odd-mode admittance are used to synthesize the low-pass network into branches of subnetworks connected in parallel between the source and the load. These together will have the same characteristics as a ladder network. It is also shown how a filter of a particular order will have the same parallel branch topology regardless of how many transmission zeros are used in the filter´s transfer function. This design technique can be beneficial for various implementation techniques such as multilayer substrate and dual-mode resonators. Examples of fourth- and sixth-order degree networks with various numbers of transmission zeros are presented.