Analysis on Multi-Stage LC Ladder Matching Circuits with Complex Terminated LC and CL Circuits

Abstract

As a mobile phone progresses with the third, fourth, and fifth generations, the frequency bands used in mobile phones are increasing dramatically. RF components for mobile phone terminals correspond to this increasing frequency band. In the case of power amplifier (PA), which is one of the RF components, it is necessary to correspond many frequency bands in one PA. In this case, the wideband of the matching circuit is a typical one of the technical problems of PA. In this study, we focus on two-stage and three-stage connections of LC ladder matching circuits widely applied in PA, and compare them from the viewpoint of broadband. In order to efficiently analyze multi-stage LC-matching circuits, the following two new methods were devised. First, we derived the analysis formula of LC and CL-matching circuits when the termination impedance was extended to a complex number. Second, we derived a condition in which the frequency derivative of the input impedance is zero.