Frequency drift

About: Frequency drift is a research topic. Over the lifetime, 5054 publications have been published within this topic receiving 56191 citations. The topic is also known as: chirp rate.

Tunable optical frequency division using a phase-locked optical parametric oscillator

Abstract: We report the experimental demonstration of a novel optical parametric oscillator approach to tunable optical frequency division. The beat frequency of the signal and idler subharmonic outputs of a tunable cw KTP optical parametric oscillator was phase locked to a microwave reference frequency source, which thus permitted precise determination of the output frequencies at approximately half the input pump frequency.

Discovery of a 270 Hertz X-Ray Burst Oscillation in the X-Ray Dipper 4U 1916–053

Abstract: We report the discovery of a highly coherent oscillation in a type I X-ray burst observed from 4U 1916-053 by the Rossi X-Ray Timing Explorer (RXTE). The oscillation was most strongly detected ≈1 s after the burst onset at a frequency of 269.4 Hz, and it increased in frequency over the following 4 s of the burst decay to a maximum of 272 Hz. The total measured drift of 3.58 ± 0.41 Hz (1 σ) represents the largest fractional change in frequency (1.32% ± 0.15%) yet observed in any burst oscillation. If the asymptotic frequency of the oscillation is interpreted in terms of a decoupled surface burning layer, the implied neutron star spin period is around 3.7 ms. However, the expansion of the burning layer required to explain the frequency drift during the burst is around 80 m, substantially larger than expected theoretically (assuming rigid rotation). The oscillation was not present in the persistent emission before the burst, nor in the initial rise. When detected, its amplitude was 6%-12% (rms) with a roughly sinusoidal profile. The burst containing the oscillation showed no evidence for photospheric radius expansion, while at least five of the other nine bursts observed from the source by RXTE during 1996 and 1998 did. No comparable oscillations were detected in the other bursts. A pair of kilohertz quasi-periodic oscillations (kHz QPOs) has been previously reported from this source with a mean separation of 348 ± 12 Hz. 4U 1916-053 is the first example of a source where the burst oscillation frequency is significantly smaller than the frequency separation of the kHz QPOs.

Performance of the BDS3 experimental satellite passive hydrogen maser

Abstract: Various types of onboard atomic clocks such as rubidium, cesium and hydrogen have different frequency accuracies and frequency drift rate characteristics. A passive hydrogen maser (PHM) has the advantage of low-frequency drift over a long period, which is suitable for long-term autonomous satellite time keeping. The third generation of Beidou Satellite Navigation System (BDS3) is equipped with PHMs which have been independently developed by China for their IGSO and MEO experimental satellites. Including Galileo, it is the second global satellite navigation system that uses PHM as a frequency standard for navigation signals. We briefly introduce the PHM design at the Shanghai Astronomical Observatory (SHAO) and detailed performance evaluation of in-orbit PHMs. Using the high-precision clock values obtained by satellite-ground and inter-satellite measurement and communication systems, we analyze the frequency stability, clock prediction accuracy and clock rate variation characteristics of the BDS3 experimental satellites. The results show that the in-orbit PHM frequency stability of the BDS3 is approximately 6 × 10−15 at 1-day intervals, which is better than those of other types of onboard atomic clocks. The BDS3 PHM 2-, 10-h and 7-day clock prediction precision values are 0.26, 0.4 and 2.2 ns, respectively, which are better than those of the BDS3 rubidium clock and most of the GPS Block IIF and Galileo clocks. The BDS3 PHM 15-day clock rate variation is − 1.83 × 10−14 s/s, which indicates an extremely small frequency drift. The 15-day long-term stability results show that the BDS3 PHM in-orbit stability is roughly the same as the ground performance test. The PHM is expected to provide a highly stable time and frequency standard in the autonomous navigation case.

Differential-logic ring oscillator with quadrature outputs

Abstract: A topology for a high speed voltage controlled oscillator (VCO) with quadrature outputs is produced utilizing four inverting differential circuits (12, 14, 16, 18). The fully differential four stage ring oscillator has outputs from alternate delay circuits combined in balanced exclusive OR gate frequency doublers (24, 26) to provide both in-phase and quadrature output signals at twice the ring oscillator frequency. The period of the quadrature delay signals is four gate delays and is easily realized in the Ghz frequency ranges. The in-phase and quadrature output signals are again combined in a balanced exclusive OR gate frequency doubler (36) to obtain a final output frequency quadruple the ring oscillator frequency.

A narrow linewidth and frequency-stable probe laser source for the 88Sr+ single ion optical frequency standard

Abstract: In this paper, we describe in detail a narrow linewidth and frequency-stable laser source used to probe the 5s2S1/2–4d2D5/2 clock transition of the 88Sr+ optical frequency standard. The performance of the laser system is investigated with studies of its frequency drift rates and with high resolution spectra of the 88Sr+ clock transition. The observed short-term drift rates are typically in the range of 10 to 23 mHz/s, and the current long-term drift rate is 13.9(3) mHz/s. The laser stability, after subtraction of linear drifts, reaches 5×10−16 at an averaging time of 3000 s. This high level of stability is attributed for the most part to stabilization of the reference cavity at the temperature where the coefficient of linear thermal expansion crosses zero. An upper bound for the laser linewidth is given by the observation of a Fourier-transform limited resonance of 4.3 Hz (Δν/ν=1×10−14) on the 88Sr+ clock transition. The effective averaging time during the linewidth measurements was about 100 s.