Test & Measurement
Fundamental breakthroughs by Symmetricom in phase noise and Allan Deviation testing have dramatically reduced the cost, complexity, effort and error typically associated with these measurements. The result is the most accurate test sets in the industry, providing phase noise measurement accuracy down to a previously impossible ±1.0db. Discover the key insights behind these advances.
The Allan variance has historically been estimated using heterodyne measurement systems, which have low noise and preserve the carrier phase information needed for longterm stability. The single-sideband phase noise has traditionally been estimated using phase detectors that suppress the carrier in order to achieve even lower noise. The recent development of the direct-digital phase noise measurement technique makes it possible to stimate both statistics accurately and simultaneously from the same time series of the phase [1]. Our comparison of the three techniques has revealed several challenges to the accurate estimation of the Allan variance including undesired aliasing, biased estimators, and spurious signal generation. Investigation of these difficulties has led to several opportunities to improve Allan variance estimation including the ability to estimate the instrumentation noise floor during a measurement and the existence of an optimum measurement bandwidth. In the end, this has led to faster, easier, more reliable, and more accurate measurement methods.
