Correction of the parameters of the equivalent circuit proposed by Montgomery for a two-terminal-pair junction

A correction to the admittance equation of the equivalent circuit for a symmetrical two-terminal-pair junction as proposed by Montgomery (1948) is presented. The circuit used by Montgomery is built with two sections of transmission lines separated by shunt admittance. The mistake in the equation was detected while using that circuit in cascade to model a microwave bandpass filter. A procedure is established and implemented to identify the mistake in the equation. Next, the correct equation is developed using the /spl Pi/ equivalent circuit. Samples of double posts in the P-band (two-terminal-pairs junctions) are built and characterised. The experimental S-parameters are applied in the equation proposed by Montgomery and in a procedure by the authors, showing excellent agreement with the latter and a constant error in Montgomery´s.