TESTED: Chip Scale Atomic Clock (Precision Timing & Frequency Reference)

This video takes a closer look at the Jackson Labs, now VIAVI Solutions Inc., Chip Scale Atomic Clock (CSAC) GPSDO, one of the first commercially available chip-scale atomic references. Built around the Microsemi SA.45s CSAC, this module represents a major step forward in precision timing: delivering atomic-clock-level stability in a dramatically smaller and lower-power package compared to traditional systems. A brief jitter analysis is performed using a LeCroy WaveRunner 640 Zi oscilloscope (4 GHz bandwidth, 40 GS/s sampling rate), offering an initial glimpse into the short-term signal integrity of the CSAC output. While this measurement is only preliminary, it highlights the clock's performance characteristics and sets the stage for more detailed analysis in future tests. The CSAC GPSDO combines a cesium vapor cell atomic oscillator with an integrated high-performance GPS receiver and time-interval counter. It can phase-lock its internal oscillator to either its own GPS-derived 1 PPS signal or an external reference, achieving typical phase accuracy better than 0.3 ns. In holdover mode, it delivers excellent long-term stability, typically better than 5E-12 per day, while consuming under 1.4 W. *Key features include:* ▸Full atomic lock in under 60 seconds (typically) ▸Sub -125 dBc phase noise at larger than 100 Hz offsets (with integrated filtering) ▸Multiple outputs: 10 MHz, 5 MHz, and 1 PPS ▸Integrated GPS receiver with WAAS/EGNOS/MSAS support ▸High-resolution (20 ps) time-interval counter ▸RS-232 and USB control via SCPI commands ▸Holdover mode with aging compensation ▸Extremely compact size with low g-sensitivity *Additional context from the manufacturer:* CSACs units themselves nowadays sell for up to $5,000 per unit. The displayed FEE value represents the Allan Deviation (ADEV) estimate over a 1,000-second averaging interval-e.g., 5E-12 corresponds to approximately ±5 ns of timing variation over that period. The interface also shows a two-minute average comparison between the CSAC clock and an external uBlox 1 PPS reference. The CSAC LCD telemetry page provides insight into internal operating parameters, including laser current, module temperature, and VCO control voltage-offering a deeper look into the behavior of this highly integrated atomic timing system. *Official product page and full specifications:* https://www.viavisolutions.com/en-us/products/chip-scale-atomic-clock-gpsdo-csac #electronics #electricalengineering #physics