On temporal correlations in high-resolution frequency counting

• Published in: arXiv.org 2016-04
• Main Authors: Dunker, Tim, Hauglin, Harald, Rønningen, Ole Petter
• Format: Article
• Language: English
• Subjects: Cables; Confidence; Connectors; Estimates; Flicker; Frequency analysis; Frequency counters; Frequency stability; High resolution; Hydrogen masers; Noise; Random walk; Test methods
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1604.05076

We analyze noise properties of time series of frequency data from different counting modes of a Keysight 53230A frequency counter. We use a 10 MHz reference signal from a passive hydrogen maser connected via phase-stable Huber+Suhner Sucoflex 104 cables to the reference and input connectors of the counter. We find that the high resolution gap-free (CONT) frequency counting process imposes long-term correlations in the output data, resulting in a modified Allan deviation that is characteristic of random walk phase noise. Equally important, the CONT mode results in a frequency bias. In contrast, the counter's undocumented raw continuous mode (RCON) yields unbiased frequency stability estimates with white phase noise characteristics, and of a magnitude consistent with the counter's 20 ps single-shot resolution. Furthermore, we demonstrate that a 100-point running average filter in conjunction with the RCON mode yields resolution enhanced frequency estimates with flicker phase noise characteristics. For instance, the counter's built-in moving-average function can be used. The improved noise characteristics of the averaged RCON mode versus the CONT mode imply that the former mode yields frequency estimates with improved confidence for a given measurement time.