Power Detector Performance and Placement Effects on Measurement Accuracy in Sampled-Network Reflectometry

This article presents an analysis of the effects of sampler characteristics and configuration on impedance measurement performance with a sampled-network reflectometer. The sampled-network approach builds on the sampled-line multi-port reflectometer to achieve impedance measurement with arbitrary matching networks, allowing integration into radio-frequency (RF) power amplifier (PA) output matching networks (OMNs). Integration into PA OMNs places unconventional constraints on sampler design and configuration, and impedance measurement performance of the system depends on the power detection characteristics of the samplers as well as their configuration within the OMN. For the first time, the effect of different types of power detector error on impedance measurement is investigated, and an experimental test structure is used to evaluate in detail how sampler response characteristics and sampler configuration affect impedance measurement accuracy. It is demonstrated how impedance measurement accuracy is dependent not only on sampler configuration, but also on the combined effect of the configuration with individual sampler characteristics, and additional samplers can improve or degrade measurement depending on their response characteristics and locations within the network. A power combining structure in a sampled network provides additional opportunities for improving impedance measurement with sampler configuration.