Large signal characterization of high speed digital buffers for signal integrity analysis of software-defined-radio applications

The advent of the software-defined-radio (SDR) concept, has placed many of the traditional analog functions of RF wireless transceivers in the digital domain, attracting an increased interest of the RF community to the characterization and modeling of digital and mixed-mode circuits such as analog-to-digital converters, digital-to-analog converters and input/output digital buffers/drivers. Therefore, this paper presents an experimental procedure to characterize high speed packaged digital buffers under large signal regime. Based on an inexpensive RF broadband bi-directional coupler, the dynamic behavior of the Pull-Down/Pull-Up networks is determined. The test fixture effects are removed through a well-defined de-embedding procedure, allowing the determination of the voltage/current at the buffer´s output. The paper also addresses the buffer´s characterization under switching conditions.