Analysis of on‐chip GSG pads coupling effects on laterally‐coupled and double‐stacked inductors in the millimeter‐wave frequency regime

Abstract

AbstractOn‐chip coupled inductors express huge nonuniform coupling tendencies, especially as frequency increases. This though desirable for wireless/galvanically isolated signal transfer but when mixed with the ground‐signal‐ground (GSG) pad could lead to a misrepresentative of the device's true coupling performance. To determine the coupling between the coupled inductors and that of the GSG pad an integrator analytical model investigating the total coupling effects of the GSG pad on laterally‐coupled and stacked inductors is presented in this study. The model characterizes the lateral and vertical coupling effects using lumped circuit elements with analytical equations. The coupling effects of each component are further decomposed and analyzed as electrical, magnetic, and combined effects. The electrical coupling effect, particularly that of the GSG pad, increases with frequency and impacts significantly on the coupled inductors and the substrate. The mm‐wave frequency characteristics such as skin and proximity effects of the inductors are also modeled by the double RL ladder network. The parameter extraction of the model is based on the measured S‐parameter data. The validation of the proposed model given the measured scattering parameter S21 dB achieves an RMSE of 0.0132 dB at 50 GHz. The inductor typology is most applicable to two‐port networks for impedance matching, cross‐coupled VCOs, and high‐speed communication networks.