Frequency Standards PRS10 — Rubidium frequency standard with low phase noise PRS10 Rubidium Frequency Standard · Low phase noise (< −130 dBc/Hz at 10 Hz) · Time-tags or phase-locks to a 1 pps input · 72 hour Stratum 1 level holdover · RS-232 for diagnostics, control and calibration · 20 year lamp life The PRS10 is an ultra-low phase noise, 10 MHz rubidiumdisciplined crystal oscillator. The device fulfills a variety of communication, synchronization and instrumentation requirements. The phase noise of the 10 MHz output is low enough to be used as the reference source for synthesizers. The unit’s short-term stability and low environmental coefficients make it an ideal component for network synchronization. Its low aging rate makes it an excellent timebase for precision frequency measurements. The PRS10 can time-tag an external 1 pps input with 1 ns resolution. These values may be reported back via RS-232, or used to phase-lock the unit to an external reference (such as GPS) with time constants of several hours. This feature can provide Stratum 1 performance at a very low cost. The PRS10 establishes a new level of features and performance in atomic frequency standards. Its design provides the lowest phase noise, greatest versatility, and easiest path to system integration of any rubidium frequency standard available. PRS10 Operation and Design All commercial rubidium frequency standards operate by disciplining a crystal oscillator to the hyperfine transition at 6.834,682,612 GHz in rubidium. The amount of light from a rubidium discharge lamp that reaches a photodetector through a resonance cell will drop by about 0.1 % when the rubidium vapor in the resonance cell is exposed to microwave Stanford Research Systems

PRS10 Rubidium Frequency Standard power near the transition frequency. The crystal oscillator is stabilized to the rubidium transition by detecting the light dip while sweeping an RF frequency synthesizer (referenced to the crystal) through the transition frequency. final frequency as the unit warms up. In the case of a problem with the physics package, the unit will suspend the frequency servo and hold the varactor voltage at the last locked value. Manufacturers of rubidium frequency standards sometimes use a crystal frequency that is an exact sub-multiple of the hyperfine transition frequency...

PRS10 Rubidium Frequency Standard GPS Tracking Frequency offsets and long-term aging of the PRS10 can be eliminated by phase-locking to a source with better long-term stability, such as the 1 pps from a GPS timing receiver. As Standard Interface Connector GPS 1pps Root Allan Variance (Parts in 1012 ) When an external 1 pps signal is applied, the PRS10 will verify the integrity of that input and will then align its 1 pps output with the external input. The processor will continue to track the 1 pps output to the 1 pps input by controlling the frequency of the rubidium transition with a small magnetic...

Output Output frequency 10 MHz sine wave Amplitude 0.5 Vrms, ±10 % Phase noise (SSB) < –130 dBc/Hz (10 Hz) < –140 dBc/Hz (100 Hz) Spurious < –130 dBc (100 kHz BW) Harmonic distortion < –25 dBc Return loss >25 dB (at 10 MHz) Accuracy at shipment ±5 × 10–11 Aging (after 30 days) Monthly <5 × 10–11 (<2.5 × 10–11 with opt. C) Yearly <5 × 10–10 Short-term stability <2 × 10–11 (1 s) (Allan variance) <1 × 10–11 (10 s) <2 × 10–12 (100 s) Holdover 72 hour Stratum 1 level Frequency retrace ±5 × 10–11 (72 hrs. off, then 72 hrs. on) Settability <5 × 10–12 Trim range ±2 × 10–9 (0 to 5 VDC) ±1 ppm (via RS-232)...