On modern and historical short-term frequency stability metrics for frequency sources

Modern frequency stability metrics employed in industry are discussed within the context of the historical development of the Allan variance. It is shown that phase noise and the first and second jitter differences are often reported in lieu of the Allan variance for frequency sources utilized in consumer electronics. This inconsistency between the historical and modern treatment of frequency stability is addressed through the presentation of analytical relationships and bounds for these common metrics. The presented expressions are compared with experimental results where good agreement is found while employing several different measurement approaches. The clear requirement for standardized metrology is motivated.