Capacitor Pi Network For Impedance Matching

PI Matching Networks

Designing matching networks is one of the key aspects of RF/Microwave design. A lossless network that matches an arbitrary load to real impedance has to have at least two reactive elements. However, two elements do not give control over the bandwidth and the degree of match simultaneously. Three-element matching networks, i.e. Pi- and Tee-networks, provide additional control of the frequency response.

In this application note we explore the idea of designing an all-capacitor Pi matching network by using one of the elements beyond its self-resonant frequency, when it has become inductive rather than capacitive. Essentially, the effective series inductance (ESL) of the series element in the Pi network is utilized. The design process is enabled via the broad-band accuracy of the Modelithics Global capacitor models, in particular those for ATC 600L 0402 capacitors. The use of method of moments co-simulation, wherein numerical electromagnetic simulation is used to represent the distributed interconnects and discrete models are used for the lumped components, is also demonstrated.