RFS-IIF

Description

The PerkinElmer RFS-IIF Rubidium Atomic Frequency Standard is an exceptionally high performance and high reliability space-qualified rubidium clock developed for the GPS Navstar navigation satellites. It offers the highest stability ever reported for a device of this type, along with the practical size, weight, power and life advantages of a rubidium gas cell atomic frequency standard. While the RFS-IIF may be operated in air, it achieves its best performance in vacuum which eliminates barometric sensitivity. All other environmental sensitivities (temperature, voltage, etc.) are negligible. The design has been fully documented and qualified for all space requirements, including radiation. The RFS-IIF offers exceptional performance as a precise time and frequency reference for demanding space applications. This PerkinElmer Rubidium Atomic Frequency Standard was developed specifically for space applications where a high stability and extremely reliable atomic clock is needed. It is the highest performance device of this type currently available, combining exceptional stability and low drift with negligible environmental sensitivity, while offering the low size, weight and power advantages of a rubidium frequency standard. The RFS-IIF employs classical rubidium gas cell atomic frequency standard principles. It utilizes a physics package with a discrete isotopic filter cell for best stability. The relatively large, cool absorption cell provides exceptionally high signal-to-noise ratio and excellent short term stability (typically 2 x 10-12 at 1 second). Calorimetric Rb lamp process control and screening assures long life. Operation at low fixed magnetic bias field improves stability and reduces magnetic and radiation sensitivity. An integral baseplate temperature controller reduces the overall temperature sensitivity to below the noise level. When operated in a vacuum environment that eliminates barometric sensitivity, the extremely low temperature, magnetic, radiation and voltage sensitivities mean that the unit is essentially free of any measurable environmental sensitivity. RFS-IIF provides a very low flicker floor (typically 2 x 10-14). The low aging rate ( A crystal oscillator at 10.23 MHz, synthesized from the Rb hyperfine resonant frequency, produces the output signal via an output amplifier. This rf output path is hardened against transient radiation. Another crystal oscillator at approximately 13.4 MHz excites the Rb physics package via a phase modulator and frequency multiplier chain. This produces a discriminator signal that is processed by a servo amplifier to lock that crystal oscillator to the Rb atomic resonance. Temperature controllers, a lamp exciter and a precision C-field source support the operation of the physics package, while a dc/dc converter and linear regulators provide power for the RFS-IIF circuits. An integral controller stabilizes the RFS-IIF baseplate temperature, and several analog monitors are available to assess the operation of the unit.