A Novel Star-Junction Multiplexer Synthesis Approach Based on Pole–Residue Update

This letter introduces a stable star-junction multiplexer synthesis method based on rational function iteration. It reformulates the objective of allocating the common port reflection zeros (CPRZs) by iteratively adjusting the input admittance (IA) of individual channel filters (CFs), ensuring that the common port IA is perfectly matched at the predefined reflection zeros. This enables the proposed method to be applied to frequency-dependent reference impedance. Furthermore, the proposed iterative procedure inherently eliminates the need for high-order polynomial manipulation and provides improved numerical stability. Two examples of synthesis are presented to demonstrate the effectiveness of this approach.