Reference Signal Synthesized from a Cryogenic Sapphire Oscillator Improved by Power Control Servo

Watabe, K.; Hartnett, John G.; Locke, Clayton R.; Santarelli, Giorgio; Yanagimachi, Shinya; Shimazaki, Takeshi; Ikegami, Takeshi; Ohshima, Shinichi

doi:10.1143/jjap.45.2827

Cited by 9 publications

(3 citation statements)

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“…9) In a previous paper, we reported that the frequency stability of the CSO for averaging times shorter than 510 s could not be directly measured. 10) It was masked by shortterm fluctuations of the reference hydrogen maser. A second CSO (CSO2) now has been built to evaluate the first CSO (CSO1).…”

Section: Introductionmentioning

confidence: 99%

Short Term Frequency Stability Tests of Two Cryogenic Sapphire Oscillators

Watabe

Hartnett

Locke

et al. 2006

Jpn. J. Appl. Phys.

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Ultra-high short-term frequency stability has been realized in microwave oscillators based on liquid helium cooled sapphire resonators which operate on the same Whispering Gallery mode. Two cryogenic sapphire oscillators were built to evaluate their stability at short averaging times. These oscillators exhibited a fractional frequency stability of 1.1×10-15 at an averaging time of 1 s, which is more than 100 times better than that of a hydrogen maser. For averaging times between 2 and 640 s the measured oscillator fractional frequency instability was below 10-15 with a minimum of 5.5×10-16 at an averaging time of 20 s. The noise floors of the control servos which contribute to the short-term frequency stability are also discussed.

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Section: Introductionmentioning

confidence: 99%

Short Term Frequency Stability Tests of Two Cryogenic Sapphire Oscillators

Watabe

Hartnett

Locke

et al. 2006

Jpn. J. Appl. Phys.

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“…The technique we used to produce a 100 MHz signal from the 10.8 GHz frequency is described in detail elsewhere. 11) In this experiment, we used the divider stage of a divide-by-10 divider to down-convert 100 to 10 MHz. For the white noise source, we used a noise source (Agilent 346B) with an excess noise ratio of $15 dB, which corresponds to a noise temperature of $9171 K. Another output of the distributed amplifier can be used for the reference signal, if necessary, when calibrating a phase noise measurement system.…”

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confidence: 99%

Signal with Flat Phase Noise Using a Carrier and the Power Spectral Density of White Noise for Phase Noise Standards

Watabe¹,

Yanagimachi²,

Ikegami³

et al. 2011

Jpn. J. Appl. Phys.

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We have realized a phase noise standard of a signal with a -100 dBc/Hz flat phase noise at 10 MHz for Fourier frequencies of 1 Hz to 100 kHz, which ensures traceability to the International System of Units (SI). The flat phase noise signal is produced using a carrier combined with white noise. To ensure traceability, both the flat phase noise signal power and the power spectral density of white noise are determined with a calibrated power meter and the noise standard, respectively. The flatness of the phase noise standard is within ±0.7 dB.

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“…Cryogenic sapphire oscillators (CSOs) [1][2][3][4] operating at microwave frequencies are capable of exhibiting a fractional frequency instability less than a part in 10 15 . Such oscillators are essential for operation of laser cooled atomic clocks at the quantum noise limit, 5 for precision tests of modern physics including the search for possible violations of Lorentz invariance, by comparing a CSO with a hydrogen-maser 6 or a CSO operating on the beat of same mode in a pair of resonators with orthogonal orientation, 7 and for searching for drift in the fine structure constants, which use fountain clocks with a CSO as the interrogation oscillator.…”

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confidence: 99%