Measuring Absolute Group Delay of Multistage Converters

This paper describes new calibration and measurement techniques for measuring absolute group delay of frequency converters with multiple mixing stages. The calibration methodology used is Agilent's Vector Mixer Calibration (VMC), where reflection measurements are used to characterize a calibration mixer, which is then used as a characterized through adapter to calibrate a frequency-translating test system for absolute magnitude and phase. The measurement methodology includes the use of a "meta-LO", which is a local oscillator derived from the LOs used for the converter under test. The meta-LO drives a reference mixer and the calibration mixer. For converters employing embedded LOs for which there is no access, but where access to a common time base is provided, an alternative measurement methodology is described.