ANTENNA MATCHING CIRCUIT, ANTENNA DEVICE, AND METHOD OF DESIGNING ANTENNA DEVICE

摘要

A switching function and multiband compatibility and a function handling deviation of matching caused by the influence of the human body are configured in a single matching circuit. An antenna matching circuit is formed by a reactance changing section and a matching section. The matching section is formed by a parallel circuit of an inductor and a capacitor, and the LC parallel circuit is shunt-connected between a feed section and the ground. The reactance changing section changes the resonant frequency to be compatible with a plurality of bands, and performs fine adjustment of the resonant frequency changed by the influence of the human body. The parallel inductor causes the locus of input impedance of the antenna matching circuit to draw a small circle locus in the first quadrant of a Smith chart. The parallel capacitor is adjustable to move the small circle locus to the center on the Smith chart.