Coupling-Routing-Diagram Modeling of Predistorted Sharp-Rejection Diplexers With Flattened-Passband Channels

The coupling-routing-diagram (CRD) modeling of a class of quasi-elliptic-type diplexer with predistorted flatenned passbands is reported. By retuning several admittance inverters of the diplexer after considering the finite quality factor (Q) of its resonating nodes, the in-band insertion-loss variation produced in its channelizing filters can be compensated. As such, an effective Q in terms of insertion-loss variation for the diplexer passbands being much higher than that intrinsic to the employed microwave technology can be achieved. For illustration purposes, the CRD modeling of two examples of flattened-passband diplexers with symmetrical- and asymmetrical-bandwidth channels, respectively, is presented. This CRD approach has potential for the design of compact/lightweight diplexers (e.g., in microstrip technology) with in-band amplitude-flatness-variation requisites being as stringent as those imposed for 3-D diplexer implementations (e.g., in waveguide technology) of satellite-communication RF receivers.