Hybrid Inductor Modeling at L-Band using 1-Port Fixtured S-Parameter Measurements

Methods for deriving accurate L-band inductor models using 1-port fixtured S-parameter measurements are presented, along with examples of modeled inductor data. The modeled inductors include both surface mount " chip" inductors with nominal values ranging from 4.7nH to 330nH, and wire-wound " leaded" inductors with nominal values from 7.5nH to 470nH. The test fixture for the surface mount inductors consists of a CoilCraft 1-port coaxial fixture, whereas a modified SMA connector was used as a test fixture for the leaded inductors. In both cases, the measurements were taken using an HP8510B network analyzer, to allow for careful modeling of the fixture. The fixture models were used to de-embed the time-delay and energy storage effects of the fixtures from the coaxially calibrated HP8510 measurements of the fixtured inductors. Using EESof's Libra CAD package and de-embedded 1-port S-parameter data, models were developed for 33 samples of 21 inductance values of chip inductors, and 22 samples of leaded inductors. The models are seen to fit the measured data over a broad band, from low RF through resonance. Models for devices which self-resonate above 1 GHz maintain close tracking to measured data over the L-band (1-2 GHz). TRL calibrated 2-port microstrip measurements of the inductors were performed to verify the models obtained from the 1-port measured data. The 2-port measurement data is seen to track the 1-port measurements well, with some uncertainty caused by the effect of the microstrip mounting gap. Simple lumped/distributed filter circuits employing the inductors also were fabricated and tested.