Modal response analysis of non‐uniform and asymmetric DL under plane‐wave illumination

Abstract

In this study, the mode-generation mechanism due to non-uniformity and asymmetry in a differential line (DL) circuit illuminated by a plane wave was analysed using a modal perturbation technique. Through modal decomposition, the field-to-line coupling equation was reformulated in terms of a differential mode (DM) and common mode, and the perturbation technique was applied, interpreting the geometrical unbalance as the mathematical equivalent modal distributed sources. Three types of typical DL structures above a loss ground with different conductivities in the frequency and time domains are discussed. The results show that the non-uniformity of a DL will cause mode perturbation, while asymmetry can lead to mode conversion. The time-domain results show that under plane-wave illumination, the DM response of an asymmetric non-uniform DL (NDL) increases significantly compared with that of a symmetric NDL and uniform DL. With the decrease in ground conductivity, the distortion of the modal response waveform is aggravated and extended with time.