Network-analyser reflection measurements of microstrip circuits not requiring exactly reproducible coaxial-to-microstrip transitions

A measuring and correction procedure for network-analyser measurements of microstrip circuits is presented which does not need exactly reproducible coaxial-to-microstrip transitions. The transmission properties of the transitions and the parameters of the microstrip lines are determined by transmission measurements of two homogeneous lines; the input reflection coefficient of the coaxial-to-microstrip transition is measured directly at the microstrip circuit under test using sliding-load techniques. Assuming the transition to have low losses, its backward reflection coefficient can be calculated approximately. The measured scattering parameters of the microstrip circuit are corrected using these values, and a measurement example shows the results of this procedure.