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

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

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

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

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

Contribution à l'analyse d'amplificateurs microondes à très faible bruit de phase (application à la réalisation d'une source à très haute pureté spectrale en bande C.)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Phase Noise Metrology and Modelling of Microwave Transistors - Applications to the design of state of the art Dielectric Resonator Oscillators

International audiencePhase noise in microwave transistors is studied both theoretically and experimentally using residual phase noise measurements. The experimental approach allows the exploration of many interesting features of phase noise generation in these devices, such as the dependence of phase noise versus microwave power or transistor low frequency loading, meanwhile nonlinear simulation is still necessary to optimise the microwave load and the whole oscillator circuit. The different behaviours described are illustrated in various microwave circuits, and particularly dielectric resonator oscillators, with some of them featuring state of the art performance

Optical Scattering Induced Noise in Fiber Ring Resonators and Optoelectronic Oscillators

14 pagesInternational audienceThis paper reports both theoretical and experimental studies on nonlinear optical phenomena generated at very low thresholds in fiber ring resonators featuring ultra-high quality factors. These studies are focused on two optical scattering phenomena: the Rayleigh and the Brillouin scatterings. The effects of these scattering phenomena on the phase noise of an optoelectronic oscillator based on the fiber ring resonator are detailed. A 30 dB reduction in the oscillator phase noise at 10 Hz offset frequency has been demonstrated by limiting the nonlinear scattering effects when using low input optical power. Moreover, a new high quality factor fiber ring resonator, optimized and immunized against some of these nonlinear optical effects, has been designed and an oscillator phase noise level of -50 dBc/Hz at 10 Hz offset frequency has been achieved