Analysis of shorted coaxial peripheral feeding networks for conical line power combiners

A simple equivalent circuit model for the peripheral ports of conical line power combiners is presented. Standard feeding pins present a series inductance in the feeding lines which limits the operating bandwidth of the structure. The presented circuit model is used to illustrate how stepping to a thickened feeding post in the conical line may reduce the feed pin inductance by introducing a shunt step capacitance in the feed line. The validity of the circuit model is confirmed by favorable comparisons with full wave simulations. Since the inductance of the feeding pins increase with length, the stepped feeding posts are crucial for good performance - especially for electrically large conical line combiners with higher impedances.