Experimental equivalent-circuit modeling of SMD inductors for printed circuit applications

An understanding of the high-frequency parasitic and packaging effects of passive surface-mounted devices (SMDs) can be gained from equivalent-circuit characterization of the device. We develop a circuit model which accurately characterizes the nonideal behavior of SMD inductors mounted on a printed circuit board (PCB), considering the device packaging and the interaction between board layout and component parasitics. The model is valid over a wide frequency band up to the first resonance of the inductor. The equivalent-circuit parameters are extracted in closed form from an accurate measurement of the S-parameters of the board-mounted SMD inductor, without the necessity for cumbersome optimization procedures normally followed in RF circuit synthesis. This procedure of measuring the component in its designed PCB environment is referred to as extrinsic characterization, in contrast to the conventional intrinsic characterization employed in RF bridges and LCR meters, which does not include the board layout effects. The developed closed-form model can be directly incorporated in commercial CAD packages, and thus, it simplifies the analysis of electromagnetic field behavior in PCBs, such as prediction of radiated emissions, signal integrity, and EMI.