Variability Analysis of Pi Network Impedance Matching

Abstract

Harmonic rejection ability and reflection coefficient are the most important factors in the design of impedance matching network. However, stability of impedance matching should be taken into account in applications existing load impedance variation and component deviation due to tolerance and process variation. This paper investigates variability of Pi network impedance matching analytically. The relationships between resulting reflection coefficient with component deviation and load impedance variation are theoretically derived on the basis of Q-based design method. The deviation from perfect match due to component deviation is proportional to quality factor. Higher quality factor probably means poorer quality in terms of variability. The resulting reflection coefficient caused by load impedance variation increases rapidly when the load reflection coefficient is larger than 0.66. A small variation in the load impedance will cause a large deviation from perfect match when the impedance difference between load and source is quite large.