An indirect measurement method for multiport S-parameters with reduced number of measurements

An indirect measurement method is proposed for the S-parameters of multiport circuit with half of its ports not directly measured. These ports are assumed to be `hard-to-access' ports. For these ports, some known loads are connected while direct measurements are performed through the remaining `easy-to access' ports to estimate the whole S-parameters. In our previous estimation method, number of measurements has to be increased to maintain the estimation accuracy when the number of ports increases. Here, we propose a novel method that applies known load sets each of which consists of mutually different loads, which is effective to eliminate the number of measurements. A numerical experiment example is shown for a circuit with “case-earth capacitors” that connect PCB ground to the body earth for noise immunity improvement in automobile application. Through the example, the validity and usability of this method is confirmed.