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Frequency Control and the European Frequency and Time Forum (FCS), 2011 Joint Conference of the IEEE International

Date 2-5 May 2011

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Displaying Results 1 - 25 of 244
  • [Front cover]

    Page(s): c1
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  • [Copyright notice]

    Page(s): ii
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  • Table of contents

    Page(s): iii - xxxix
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  • [Front matter]

    Page(s): xl - lxxviii
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  • Trapping induced frequency shifts by comparison of two Sr optical lattice clocks at the 10−17 level

    Page(s): 1
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    We present a comprehensive study of the frequency shifts associated with the lattice potential in Sr lattice clocks. By comparing two such clocks with a frequency stability better than 5.10-17 after one hour of averaging time, and varying the lattice depth up to U0 = 900 Er with Er being the recoil energy, we evaluate lattice related shifts with an unprecedented accuracy. View full abstract»

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  • Improving the stability and accuracy of the Yb optical lattice clock

    Page(s): 1 - 3
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    We report results for improving the stability and uncertainty of the NIST 171Yb lattice clock. The stability improvements derive from a significant reduction of the optical Dick effect, while the uncertainty improvements focus on improved understanding and constraint of the cold collision shift. View full abstract»

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  • Hybrid MEMS resonators and oscillators

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1413 KB) |  | HTML iconHTML  

    With quality factors (Q) often-exceeding 10,000, vibrating micromechanical resonators have emerged as leading candidates for on-chip versions of high-Q resonators used in wireless communications systems. However, as in the case for transistors, extending the frequency of MEMS resonators generally entails scaling of resonator dimensions. Unfortunately, smaller size often coincides with lower-power handling capability and increased motional impedance. In this paper we introduce novel transduction techniques which can improve the motional impedance of MEMS resonators by 1000× over traditional 'air-gap' transduced resonators, present latest results on narrow-bandwidth parametric filters for frequency-agile radio receivers, and discuss performance scaling of NEMS resonators to X-band frequencies. View full abstract»

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  • A CMOS-compatible 24MHz poly-SiGe MEMS oscillator with low-power heating for frequency stabilization over temperature

    Page(s): 1 - 5
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    MEMS based timing devices have been proposed as an alternative to Quartz systems for certain applications. Through using an oven-controlled system it is possible to stabilize the frequency response of such a MEMS system over a large ambient temperature range. This work presents a BAW MEMS resonator in poly-SiGe which achieves significantly lower power consumption for frequency stabilization over temperature through Joule heating than for a similar system in SOI, while showing promising phase noise performance in an oscillator setup. Since the poly-SiGe resonator can be processed on top of standard CMOS, this enables the possibility of full integration of an Oven-Controlled MEMS Oscillator. View full abstract»

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  • Mechanically-coupled CMOS-MEMS free-free beam resonator arrays with two-port configuration

    Page(s): 1 - 4
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    Integrated CMOS-MEMS free-free beam resonator arrays operated in a standard two-port electrical configuration simultaneously with low motional impedance and high power handling capability centered at 10.5 MHz have been demonstrated by the combination of pull-in gap reduction mechanism and mechanically-coupled array design. The mechanical links (i.e., coupling elements) using short stubs connect each constituent resonator of an array to its adjacent ones at the high-velocity vibrating locations to accentuate the desired mode and reject all other spurious modes. A single second-mode free-free beam resonator with quality factor Q >; 2,200 and motional impedance Rm <; 150 kQ has been utilized to achieve mechanically-coupled resonator arrays in this work. In array design, a 9-resonator array has been experimentally characterized to have around 10X performance improvement on motional impedance and power handling as compared with that of a single resonator. In addition, two-port electrical configuration is much preferred due to its low feedthrough nature and high design flexibilities for future oscillator and filter implementation rather than its one-port counterpart. View full abstract»

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  • Bulk modes in silicon crystal silicon

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (377 KB) |  | HTML iconHTML  

    Bulk dilation modes in rectangular plates of particular orientations in single crystal silicon are found to have distinct advantages over to those in isotropic materials. Finite element modeling using an anisotropic model reveals plates aligned to the <;110>; direction in (100) silicon have modes which offer excellent capacitive coupling and good isolation to the supports. Low impedance and high Q are predicted for select geometries. Experimental results are included, showing a 100-MHz resonator having an unloaded Q of 90,000, which demonstrate an f-Q product of ~1×1013. View full abstract»

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  • ACES MWL status and test results

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (585 KB) |  | HTML iconHTML  

    Atomic Clock Ensemble in Space (ACES) is a mission using high-performance clocks and links to test fundamental laws of physics in space. The ACES microwave link (MWL) will make the ACES clock signal available to ground laboratories equipped with atomic clocks. The ACES MWL will allow space-to-ground and ground-to-ground comparisons of atomic frequency standards. The MWL comprises the Flight Segment (FS) as part of the ACES payload as well as a distributed set of Ground Terminals (GT), collocated with the ground atomic clocks. MWL is a two-way, two-frequency link transmitting a carrier signal modulated by a PN code, both phase coherent with the local clocks. MWL is designed to reach a time resolution (TDEV) of 0.3 ps in less than 300 s of integration time. In addition to the MWL, operating in microwave domain, ELT is an optical link based on the exchange of laser pulses detected and time stamped in MWL in the local time scale in space and on ground. The engineering model of the MWL FS and the first prototypes of the MWL GT will be used for end-to-end testing of the MWL performance. The end-to-end test is using a set-up, where the MWL FS and GT are connected by cables through a test equipment that allows the full simulation of the signal dynamics during an overflight of the ISS over a MWL GT. The MWL design and test results of the individual elements will be briefly reported. The results of the end-to-end test will be presented and perspectives for clock comparisons with ACES discussed. View full abstract»

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  • Single-frequency time and frequency transfer with Galileo E5

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (366 KB) |  | HTML iconHTML  

    The GNSS main technique currently used for accurate time and frequency transfer is the so-called “geodetic time transfer”, based on a consistent modeling of dual-frequency code and carrier-phase measurements. This technique enables frequency transfer with an uncertainty of 0.1 nanoseconds thanks to the very low noise level of the carrier phase measurements, but the accuracy of time transfer can only reach the level of a couple of nanoseconds in the best cases, due to the noise and multipath of the GPS and GLONASS codes. However, in the near future Galileo will offer one promising signal, namely the broadband signal E5, with an ultimate low range noise in the cm range and with the lowest multipath error impact observed before. This paper investigates the use of this precise code for accurate time transfer. View full abstract»

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  • New realization strategy for UTC(PTB)

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (447 KB) |  | HTML iconHTML  

    The Physikalisch-Technische Bundesanstalt (PTB) realizes its atomic time scale UTC(PTB) as approximation to the international time reference UTC. It serves as the basis for PTB's time services, for the local clock comparisons and for international time comparisons. Since February 2010 UTC(PTB) has been realized using an active hydrogen maser steered in frequency via a phase micro stepper according to an algorithm described in this paper. Thereby the long-term stability and accuracy of PTB's primary clocks is combined with the typical short-term frequency stability of a hydrogen maser. During the last 12 months, the caesium fountain clock CSF1 was used as the steering reference on more than 98% of the days, which resulted in an excellent stability of UTC(PTB). During the last six months, including March 2011, its deviation from UTC was less than 4 ns. View full abstract»

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  • Contribution to TAI frequency by a travelling primary frequency standard

    Page(s): 1 - 3
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    The Mobile Atomic Fountain has been used to steer the TAI frequency when operating in sites without regular link to BIPM. A brief description of the method used to link this standard to a fly-wheel clock included in BIPM database and results are presented. There is no evidence of different behavior when the FOM is sitting in LNE-SYRTE or in remote laboratories. View full abstract»

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  • Comparing room temperature and cryogenic cesium fountains

    Page(s): 1 - 3
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    We have compared the frequency of a room-temperature cesium-fountain primary frequency standard with that of a cryogenic (~80K) cesium fountain. This comparison yields a measurement of the blackbody frequency shift of the room-temperature fountain. View full abstract»

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  • Uncertainty evaluation of the continuous cesium fountain frequency standard FOCS-2

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (903 KB) |  | HTML iconHTML  

    The continuous atomic fountain primary frequency standard FOCS-2 is quite unique since all the atomic fountain clocks presently contributing to the international atomic time (TAI) are operating in pulsed mode [1]. Our alternative approach offers the possibility to operate with a high atomic flux without the collisional shift limiting the accuracy or the Dick effect limiting the stability when a quartz is used as local oscillator [2], [3]. Moreover, it contributes to the metrological diversity since the relative importance of the error budget contributors is different in the two types of fountains, notably for microwave cavity and density related effects. In this contribution we present the status of the metrological evaluation of the continuous fountain FOCS-2. Thanks to an innovative atomic beam source followed by an atomic state preparation stage, we reach a signal-to-noise ratio of 600√Hz and thus a relative frequency instability of 6 × 10-14 T-1/2. A detailed investigation of the frequency shifts which are specific to the continuous operation (light-shift from the source and cavity end-to-end phase shift) shows that the continuous fountain is compatible with an inaccuracy at the 10-15 level or below. View full abstract»

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  • Improved accuracy evaluation of the NPL-CsF2 primary frequency standard

    Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (41 KB) |  | HTML iconHTML  

    Presented is quantitative evaluation of two leading uncertainties in the NPL-CsF2 fountain frequency standard. The distributed cavity phase shift evaluation is based on recent theoretical model where the cavity field is decomposed into a series of 2D Fourier components in azimuthal angle in the cylindrical cavity. Predictions of the model are reproduced experimentally. The microwave lensing effect is caused by dipole forces originating from radial variation of the microwave field amplitude and cavity apertures. The new evaluation of the two effects together with other recent improvements reduce the total type B uncertainty of NPL-CsF2 to 2.3 × 10-16. View full abstract»

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  • Measurements with multiple operational fountain clocks

    Page(s): 1 - 3
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    Performance of the first two operational rubidium fountains at the USNO is presented using relative measurements and comparisons against other timescales. Recent results with four fountains indicate frequency agreement at the 10-15 level and good agreement with the primary frequency standards contributing to TAI. View full abstract»

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  • Quantitative evaluation of distributed cavity phase shifts to improve the accuracy of SYRTE FO2

    Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    We report measurements and ab initio calculations of the distributed cavity phase (DCP) shifts of the LNE-SYRTE FO2 atomic fountain clock. The measurements and validated model provide the first complete and quantitative evaluation of the DCP shift in an atomic fountain, reducing the FO2 DCP uncertainty to ±8.4×10-17. Here we emphasize the experimental techniques that precisely determine the fountain parameters to stringently test the DCP model. View full abstract»

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  • Piston temperature measurement with SAW sensors

    Page(s): 1 - 5
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    In this contribution we introduce a new approach for a piston temperature measurement system based on surface acoustic wave (SAW) resonators sensitive to temperature. The approach offers a new and competitive way to support the development of pistons and allows the research and improvement in combustion processes. View full abstract»

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  • Characterization of WO3 layers deposited on quartz and lithium niobate SAW resonators for the design of gas sensors

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (814 KB) |  | HTML iconHTML  

    Surface acoustic wave (SAW) gas sensors generally require the use of a reactive layer for molecule adsorption. WO3 has been identified for a long time as a high potential sensitive layer particularly for NH3, NOX, CO, etc. We report here on the characterization of elastic properties of such material using the dispersion behavior of SAW propagating under gratings passivated wich WO3 films of various thicknesses. Quartz as well as LiNbO3 SAW devices are used in that purpose, allowing for the derivation of a reliable data set. Complementary structural characterization using direct measurement techniques (DRX, AFM, TEM,) are reported to confirm the analysis deduced from SAW measurements. As a conclusion, the exploitation of WO3 for SAW-based sensor is discussed. View full abstract»

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  • Langasite SAW temperature and oxygen multi-sensor

    Page(s): 1 - 4
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    We report here a langasite SAW device suitable for sensing temperature and oxygen concentration, with applications such as monitoring the exhaust of oxy-fuel combustion systems. In this paper we report on the observed temperature dependence of oxygen sensitivity, explain the mechanism for this behavior, and present a scheme for temperature compensation. View full abstract»

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  • SAW sensor correlator system performance parameters

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (971 KB) |  | HTML iconHTML  

    There has been little published data on spread spectrum SAW RFID correlator receiver performance, since most approaches published have used an FMCW system. The purpose of this paper is to discuss issues related specifically to correlator receiver performance parameters with respect to range, detection, and noise. The minimum detectable signal (MDS) at the ADC is used as the measure for prediction of the maximum range. The loop gain of the system, MDS, noise and processing gain bound the predicted achievable range for a correlator receiver. It will be shown that in a correlator receiver nano- to micro-joules of energy can obtain ranges greater than 50 meters, dependent on the key system parameters. A model is developed for prediction of the maximum range as a function of center frequency, output signal and power, MDS, synchronous interrogation, and loop gain. From the predictions, it appears feasible to have a sensor range of over 100 meters with modest interrogation energy in a pulsed correlator system. View full abstract»

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  • Elasto-acoustic properties of ReCa4O(BO3)3 (Re=La, Pr, Nd, Y, Gd) piezoelectric crystals

    Page(s): 1 - 4
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    Oxyborate single crystals, ReCa4O(BO3)3 (Re=La, Pr, Nd, Y. Gd), have recently been demonstrated to offer superior dielectric, piezoelectric and electromechanical properties to quartz, langasite and other commonly used piezoelectric crystals. Of particular significance is the ability to function at temperatures >; 1000°C, offering the potential for SAW, BAW and related sensors operational in harsh environments. In this work, the elasto-acoustic properties of oxyborate crystals were investigated as a function of rare earth cation. Crystallographic relationships were determined to be related to bond length and dependence of cation ordering, which was also reflected in the mechanical loss. Parameters related to high temperature operation, including electrical resistivity, dielectric loss, together with temperature dependent electromechanical and elastic properties were determined and discussed in relation to various applications. View full abstract»

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  • Modeling phase noise in multifunction subassemblies

    Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1405 KB) |  | HTML iconHTML  

    Obtaining requisite phase noise performance in hardware containing multifunction circuitry requires accurate modeling of the phase noise characteristics of each signal path component, including both absolute (oscillator) and residual (non-oscillator) circuit contributors. This includes prediction of both static and vibration-induced phase noise. The model (usually in spreadsheet form) is usually refined as critical components are received and evaluated. Additive (KTBF) phase noise data can be reasonably estimated, based on device drive level and noise figure. However, accurate determination of component near-carrier (multiplicative) and vibration-induced noise usually needs to be determined via measurement. The model should also include the effects noise introduced by IC voltage regulators and discriminate between common vs. independent signal path residual noise contributors. View full abstract»

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