Analysis of strip‐line circuit by planar circuit approach—Application of higher‐mode impedance concept

Abstract

AbstractTriplate‐line circuit and strip‐line circuit are the circuit structures used frequently at microwave and millimetric wave frequency bands. In these frequency bands, the strip‐line width is not negligible compared with the wavelength. Also, the presence of electromagnetic field disturbance at junction and the mutual interaction of the frequency bands has strong effects on frequency characteristics. In this paper, to treat this kind of problem, the strip transmission line circuit is modeled and it is shown that the electromagnetic field distribution in this model is determined by the planar circuit equations. In solving these planar circuit equations, the circuit is separated into transmission line and junction circuit, and the mode impedance for each circuit is derived. It is shown that the input/output characteristics of the strip‐line circuit are obtained by making analogous circuit equations conventional equations and solving them. This method of analysis is applied to a simple triplateline circuit and its wideband frequency characteristic is calculated for dc 18 GHz. Furthermore, the corresponding circuit is constructed and its frequency characteristic is measured for 4 ± 18 GHz. Since the calculated results based on this method of analysis agrees well with the measured results, the validity of this method of analysis is confirmed.