Figures of merit and performance measurements for RF and microwave tunable matching networks

RF and microwave tunable matching networks (TMNs) development is quickly growing as increasing their interest and demand for applications in wireless and mobile communication systems. Although this topic has been extensively reported in the literature in the last years, there are still some unclear issues regarding the performance measurements and the best figures of merit to accurately characterize these circuits. In this paper, we present an overview of some usual metrics with their pros and cons, focusing mainly in the Smith chart coverage concept and in the losses definition. We also introduce the concept of TMN gain. To illustrate this study, we will use a fabricated and measured TMN based on silicon-glass PIN diodes as switching elements.