Advanced bridge instrument for the measurement of the phase noise and of the short-term frequency stability of ultra-stable quartz resonators

High-stability quartz oscillators are needed in a number of space applications. A short-term stability of parts in 10^{-14} [Allan deviation σy(τ) ] is sometimes required, for integration time τ of approximately 1-10 s. The Centre National d'Etudes Spatiales (CNES) and the FEMTO-ST Institute (formerly LPMO and LCEP), have been collaborating for many years in this domain, aiming at measuring and at understanding the oscillator noise. The highest stability has been observed on 5 MHz and 10 MHz bulk acoustic-wave resonators. Yet this stability is still not sufficient, or the the manufacturing method is not reproducible. Recently, the analysis of a few premium-stability oscillators has demonstrated that the oscillator frequency instability is due to the fluctuation of the resonator natural frequency, rather than to the noise of the sustaining amplifier via the Leeson effect. It is therefore natural to give attention to the measurement of the resonator fluctuations

Volume Dependence in Handel's Model of Quartz Crystal Resonator Noise

International audienceAlthough criticized by many, Handel's quantum model for 1/f noise remains the only model giving a quantitative estimation of the level of intrinsic 1/f noise in quartz crystal resonators that is compatible with the best experimental results. In this paper, we reconsider the volume dependence in this model. We first argue that an acoustic volume, representing the volume in which the vibration energy is trapped, should be used instead of the geometrical volume between the electrodes. Then, we show that because there is an implicit dependence of the quality factor of the resonator with its thickness, the net effect of Handel's formula is not an increase of noise proportionally to the thickness of the resonator, as could be naïvely expected, but a net decrease when thickness increases. Finally, we show that a plot of Q4Sy versus the acoustic volume, instead of the usual Sy plot, could be useful to compare the quality of acoustic resonators having very different resonance frequencies

analysis of noise origin in ultra stable resonators: Preliminary Results on Measurement bench

The Centre National d'Etudes Spatiales (CNES), Toulouse, France and FEMTO-ST Institute, Besancon, France, have initiated a program of investigations on the origins of noise in bulk acoustic wave resonators. Several European manufacturers of high quality resonators and oscillators take part in this operation. Tests and measurements are mainly performed on an advanced phase noise measurement system, recently set up for this program. The bench principle uses carrier suppression technique. The carrier signal of the driving source is split into two equal parts to drive both crystal resonator pairs. Noise of both resonators is measured through symmetrical ways in order to suppress the source noise. Investigations on the sensitivity of selected quartz crystal resonators to various externally-controlled parameters such as temperature, drive level, load impedance, and series capacitance are presented. Various batches of different types of 5 and 10 MHz quartz crystal resonators provided by the industrial partners have already been tested (conventional, QAS, BVA, ...). Results are discussed with a special attention on some specific topics. The influence of the temperature is particularly studied according to the operating point versus the quartz crystal turn over temperature. A double enclosure and two thermally controlled ovens are used in order to control the quartz crystal temperature. The temperature step can be lower than 0.05°C between two remote-controlled operating temperatures around 80 °C. Measurements are compared to a review of theoretical aspect of temperature effects in quartz crystal resonators. In the measurement system, the resonator frequency of each arm of the bench has always to be tuned, as in an oscillator. This is fulfilled by a series capacitor having a pull-up effect. Several sets of measurements have been compared. Resonator noise is observed according to the input power in the bench arm. The frequency tuning is achieved with the series capacitor or with the source frequency. Resonator noise is also measured at constant resonator power according to a wide range of series capacitors. The tuning capacitor modifies the overall impedance, thus, correlation between load impedance and the flicker noise of the resonator is analyzed through the previous measurements. Finaly, a discussion about the contributions of the different parameters to the measurement results is done

A Program to Analyse the Origin of Noise in Ultra- Stable Quartz Crystal Resonators

International audienceIn the mid 90s the quartz crystal oscillator attained a stability in the upper 10–14 (flicker floor of the Allan deviation σy(τ), which occurs at τ =1..10 s). As a matter of fact, the highest stability was obtained with bulk-acoustic-wave quartz crystal resonators at 5 MHz and at 10 MHz. Since, the research for higher stability seems to be at a standstill, while space applications are more and more demanding. Recently, the analysis of a few premium-stability oscillators has shown that the oscillator frequency instability is due to the fluctuation of the resonator natural frequency, rather than to the noise of the sustaining amplifier via the Leeson effect. It is therefore natural to give attention to the measurement of the resonator fluctuations. The Centre National d'Etudes Spatiales (CNES) and FEMTO-ST Institute have started a research program on the origin of noise in 5 MHz and 10 MHz quartz crystal resonators. Several European manufacturers of high-stability resonators and oscillators participate. This article reports on the present status and on the future plans of this program. The first part consists in the analysis of the sensitivity of selected resonators to various externally-controlled parameters, like temperature, drive power, load impedance, series capacitance. The second part, planned, consists of listing the possible causes of noise, and of modeling their effects on frequency stability. Tests and measurements are mainly performed on an advanced phase noise measurement system, recently set up for this program. Of course, this program is a unique opportunity to test various batches of 5 MHz and 10 MHz resonators provided by the industrial partners

Applications of the optical fiber to the generation and to the measurement of low-phase-noise microwave signals

The optical fiber used as a microwave delay line exhibits high stability and low noise and makes accessible a long delay (>100 microseconds) in a wide bandwidth (about 40 GHz, limited by the optronic components). Hence, it finds applications as the frequency reference in microwave oscillators and as the reference discriminator for the measurement of phase noise. The fiber is suitable to measure the oscillator stability with a sensitivity of parts in 1E-12. Enhanced sensitivity is obtained with two independent delay lines, after correlating and averaging. Short-term stability of parts in 1E-12 is achieved inserting the delay line in an oscillator. The frequency can be set in steps multiple of the inverse delay, which is in the 10-100 kHz region. This article adds to the available references a considerable amount of engineering and practical knowledge, the understanding of 1/f noise, calibration, the analysis of the cross-spectrum technique to reduce the instrument background, the phase-noise model of the oscillator, and the experimental test of the oscillator model.Comment: 23 pages, 13 figures, 41 reference

About Quartz Crystal Resonator Noise: Recent Study

The first step, before investigating physical origins of noise in resonators, is to investigate correlations between external measurement parameters and the resonator noise. Tests and measurements are mainly performed on an advanced phase noise measurement system, recently set up. The resonator noise is examined as a function of the sensitivity to the drive level, the temperature operating point and the tuning capacitor.Comment: 20th International Conference on Noise and Fluctuations, Pisa : Italie (2009

About the role of phase matching between a coated microsphere and a tapered fiber: experimental study

nombre de pages 10International audienceCoatings of spherical optical microresonators are widely employed for different applications. Here the effect of the thickness of a homogeneous coating layer on the coupling of light from a tapered fiber to a coated microsphere has been studied. Spherical silica microresonators were coated using a 70SiO2 - 30HfO2 glass doped with 0.3 mol% Er3+ ions. The coupling of a 1480 nm pump laser inside the sphere has been assessed using a tapered optical fiber and observing the 1530-1580 nm Er3+ emission outcoupled to the same tapered fiber. The measurements were done for different coating thicknesses and compared with theoretical calculations to understand the relationship of the detected signal with the whispering gallery mode electric field profiles

High-resolution microwave frequency dissemination on an 86-km urban optical link

We report the first demonstration of a long-distance ultra stable frequency dissemination in the microwave range. A 9.15 GHz signal is transferred through a 86-km urban optical link with a fractional frequency stability of 1.3x10-15 at 1 s integration time and below 10-18 at one day. The optical link phase noise compensation is performed with a round-trip method. To achieve such a result we implement light polarisation scrambling and dispersion compensation. This link outperforms all the previous radiofrequency links and compares well with recently demonstrated full optical links.Comment: 11 pages, 5 figure

A simple method for in vivo labelling of infiltrating leukocytes in the mouse retina using indocyanine green dye

We have developed a method to label and image myeloid cells infiltrating the mouse retina and choroid in vivo, using a single depot injection of indocyanine green dye (ICG). This was demonstrated using the following ocular models of inflammation and angiogenesis: endotoxin-induced uveitis, experimental autoimmune uveoretinitis and laser-induced choroidal neovascularization model. A near-infrared scanning ophthalmoscope was used for in vivo imaging of the eye, and flow cytometry was used on blood and spleen to assess the number and phenotype of labelled cells. ICG was administered 72 h before the induction of inflammation to ensure clearance from the systemic circulation. We found that in vivo intravenous administration failed to label any leukocytes, whereas depot injection, either intraperitoneal or subcutaneous, was successful in labelling leukocytes infiltrating into the retina. Progression of inflammation in the retina could be traced over a period of 14 days following a single depot injection of ICG. Additionally, bright-field microscopy, spectrophotometry and flow cytometric analysis suggest that the predominant population of cells stained by ICG are circulating myeloid cells. The translation of this approach into clinical practice would enable visualization of immune cells in situ. This will not only provide a greater understanding of pathogenesis, monitoring and assessment of therapy in many human ocular diseases but might also open the ability to image immunity live for neurodegenerative disorders, cardiovascular disease and systemic immune-mediated disorders

Spectral density of phase noise inter-laboratory comparison final results

This paper reports main results of the phase noise comparison that has been performed between october 2005 and december 2006, using two oscillators at 5 and 100 MHz and un DRO at 3.5 GHz. The problem is not to compare the performances of several oscillators, but to compare and to make an evaluation of the uncertainties, and of course the resolution and the reproducibility of the measurements. This comparison allow us to determine the ability to get various systems traceable together in order to increase the trust that one can have in phase noise measurements