PRS10 Rubidium Frequency Standard

Source: Stanford Research Systems (SRS)
The PRS10 is an ultra-low phase noise 10 MHz frequency standard
The PRS10 is an ultra-low phase noise 10 MHz frequency standard that disciplines a crystal oscillator to a hyperfine transition in the ground state of rubidium.

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 RS232 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 a 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 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.

The PRS10 uses a microcontroller, clocked at 10 MHz, to control all aspects of operation and to allow diagnostics, measurement, and closed case calibration via an RS232 interface. The processor sweeps the RF synthesizer, synchronously detects the optical signal from the physics package, and servos the 10 MHz crystal oscillator to the rubidium transition via a 22-bit DAC and a varactor.

  • Low phase noise (<-125 dBc/Hz at 10 Hz)
  • Time-tags or phase-locks to a 1 pps input
  • Slewable 1 pps output with 1 ns resolution
  • RS232 for diagnostics, control and calibration
  • Long lamp life and established reliability
  • Low cost

Stanford Research Systems (SRS), 1290-D Reamwood Avenue, Sunnyvale, CA 94089. Tel: 408-744-9040; Fax: 408-744-9049.