A spiral inductor shows a skin effect where, as frequency is increased, current is concentrated on a surface of a conductor. A spiral inductor also shows a proximity effect where upon bringing another conductor in proximity with the spiral inductor, a high frequency current is more intensively flowed into a portion close to the other conductor. In order to represent these two effects in an equivalent circuit of the inductor, a coupling form of a 2-π equivalent circuit model that is a modification of an existing single-π model was recently disclosed in an article and is shown in FIG. 1.
However, the 2-π equivalent circuit model has problems in that the extraction of the model is complicated and a large error can be generated in the value of the extracted parameter.