A simple method for restoring passivity in S-parameters using singular value decomposition

With new high speed data standards, such as USB 3.0, data rate has increased up to 5 Gbps (a 10-fold increase from USB 2.0) creating new challenges for a design engineer. Amid these speeds, issues like crosstalk, signal integrity and bit-error rates are coming to the forefront of the design cycle, especially for consumer electronics-related devices. Therefore, there is a need of accurate methods to characterize device behavior at high frequencies. For instance, S-parameter characterization of high speed interconnect components by full wave field solvers, macromodels and physical measurement are prone to numerical, modeling, and measurement error. This error can lead to nonphysical results such as passivity violations. This is a major problem in modern package design where extensive signal integrity simulations are required to validate a systems performance and passivity violations can cause such simulations to fail completely. This paper presents a new method for restoring passivity to non-passive S-parameter data by using singular value decomposition. Simulations show promising results although the method is limited to passivity violations of 1dB.