Ultra-High Stability Microwave Oscillators

Frequency Standards Laboratory

Cryogenic microwave oscillators with very high quality factors (Q's) show unparalleled short term frequency stability and ultra-low phase noise. JPL is developing new technologies based on "whispering gallery" sapphire resonators. The resonator configurations shown here are designed for increased reliability and reduced refrigeration requirements using advanced analytical tools. A new frequency standard, the 10 Kelvin Compensated Sapphire Oscillator, is now under construction to provide an ultra-high stability short-term frequency reference for the Cassini Mission. Continuous operating periods of a year or more are expected.

Just as a long-distance runner has a different build from that of a sprinter, several distinct frequency standard technologies are required to operate the Deep Space Network - depending on for how long we need to keep time.
Short-term frequency standards make possible radio science experiments that measure the relatively quick signal fluctuations that occur when the radio path to the spacecraft traverses e.g. one of Saturn's rings. They also provide a "flywheel" oscillator capability that enables advanced atomic standards such as JPL's LITS to achieve their ultimate stability.

10K Compensated Sapphire Oscillator

With a sapphire resonator optimized for temperatures that can be reached by commercial cryocoolers, the 10K CSO has no consumables and can operate continuously for periods of a year or more. It is designed to provide 10^-15 stability for the Cassini Ka-band Experiment. The first two units are now being assembled and tested.

77K CSO

The 77K CSO added external compensation to a sapphire resonator, cancelling sapphire's inherent temperature sensitivity by thermal expansion in a central copper post. Cooled by inexpensive liquid nitrogen, this standard paved the way for a new generation of ultra-high stability sapphire oscillators that don't need liquid helium.

Cyres Finite Element Modeling Software

Accurate modeling of sapphire resonators is difficult except for relatively simple geometries where analytical models can be used. CYRES finite element software gives great freedom of design while properly taking into account the particular directional characteristics of sapphire.

Superconducting Cavity Maser Oscillator

The SCMO was the first JPL-developed cryogenic oscillator with ultra high (10^-15) stability. Cooled by liquid helium it combines superconducting, sapphire and ruby maser technologies.

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