Improved characterization of differential multi-Ghz integrated amplifiers and filters

Accurate characterization of fully differential on-chip filters and amplifiers whose bandwidths extend to several GHz is challenging. Measurement using a packaged chip is convenient, but not accurate due to nonidealities of the package. In this work, we demonstrate that the use of on-chip polarity reversal buffers greatly enhances accuracy by reducing the effect of finite package isolation and by mitigating errors due to common-mode to differential mode conversion. Further, the technique also allows differential characterization using only two-port single-ended measurements, without compromising much on accuracy. Measurements on an integrated 7 GHz Bessel filter made using this technique show good consistency up to 20 GHz whether the chip is probed or bench characterized after mounting in a QFN package.