Design and Characterization of Bias Tee Used for S-parameter Characterization of Power Inductors

This paper presents the design and characterization of the bias tee for S-parameter characterization of surface-mount power inductors used in switching power converters. The bias tee is used to vary DC current through the measured power inductor. The equivalent circuit models of the inductive and capacitive elements are imported into the circuit simulator. The insertion loss, reflection loss and isolation are obtained from the simulations in the frequency range from 300 kHz to 100 MHz. The bias tee is designed on a dual layer printed circuit board and characterized using the vector network analyzer. The impedance characteristics of a 4.7-μH power inductor are extracted from measurements up to 100 MHz using the designed bias tee.