IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

We describe the operation of a laser cooled /sup 87/Rb frequency standard and present a new measurement of the /sup 87/Rb ground state hyperfine frequency with a relative accuracy of 2.4/spl times/10/sup -15/, by comparison with a Cs fountain primary standard. The measured frequency is 6 834 682 610.904 333(17) Hz. An evaluation of the frequency shift induced by cold collisions gives /spl Delta//s... View full abstract»

A cryocooled compensated sapphire oscillator (CSO), developed for the Cassini Ka-band Radio Science experiment, and operating in the 7 K-10 K temperature range, was demonstrated to show ultra-high stability of /spl sigma//sub y/=2.5/spl times/10/sup -15/ for measuring times 200 seconds /spl les//spl tau//spl les/600 seconds using a hydrogen maser as a reference. CSO-1 and CSO-3 are now both operat... View full abstract»

Total variance represents the first advancement in the estimation of an oscillating signal's long-term frequency stability since the conventional Allan variance estimator. It is called "Totvar" (pronounced tot-var) for short. Its commonly reported square-root is the total deviation function called "Totdev" (tot-dev). Totdev efficiently extracts broadband FM oscillator noise levels and types common... View full abstract»

For the past two years we have been implementing a program for the establishment of scientific time and frequency metrology in Brazil. The main objective of this program is to construct an atomic fountain and use it as a primary standard. As a first step toward this goal, we have constructed a /sup 133/Cs beam optically pumped conventional clock. In this paper we describe the system and the result... View full abstract»

The amplitude noise responses of optical-frequency-discriminating systems, based on Fabry-Perot cavities with intensity noise compensation, are analyzed considering also the effect of the resonator transient. From the point of view of amplitude noise immunity, systems based on transmission or reflection alone behave in a quite similar way within the discriminator bandwidth, whereas a proper combin... View full abstract»

The performance of a simple microwave frequency reference based on Raman scattering in an atomic vapor is examined. This reference has the potential to be compact, low-power, and insensitive to acceleration. Several design architectures have been evaluated with a table-top experiment in order to guide the future development of a compact system. Fractional frequency deviations of /spl les/5/spl tim... View full abstract»

Frequency divide-by-two (2:1) and divide-by-three (3:1) optical parametric oscillators (OPOs) are basic devices for the implementation of future accurate optical frequency division chains. We report our latest development toward a phase-locked 3:1 frequency division of a radiation at /spl lambda//sub p//spl ap/843 nm (355.9 THz), using doubly resonant oscillators (DROs) based on silver gallium sul... View full abstract»

Atomic Clock Ensemble in Space (ACES) is a project of the European Space Agency on-board the future International Space Station (ISS). The payload consists mainly of two atomic frequency standards, one space hydrogen maser (SHM) prepared by the Observatoire de Neuchatel (Switzerland), and one cold atom caesium clock called PHARAO prepared by the CNES (France), with the participation of the BNM-LPT... View full abstract»

This paper describes the software and equipment used at the Laboratoire Primaire du Temps et des Frequences du Bureau National de Metrologie (BNM-LPTF), Paris, France. Two H-masers in short baseline, one located at the BNM-LPTF and the other at the Laboratoire de l'Horloge Atomique du Centre National de la Recherche Scientifique (CNRS-LHA), Orsay, France, were computed in parallel with the BNM-LPT... View full abstract»

Properties of the phase fluctuations of a nonlinear oscillator were investigated. The multiscale aspect of synchronization is experimentally confirmed with the observation of lockings at any rational ratio. This global property of synchronization is associated with a local one by the study of the phase locked loop (PLL) under nonlinear conditions. We show that the discontinuity between the locking... View full abstract»

In frequency standards in which the atoms have a continuous interaction with the probe signal, local oscillator phase noise may limit medium term frequency stability. This spurious effect cannot be suppressed whenever there Is any truncation in the spectrum of the resonator response. Nevertheless, a simultaneous processing of the probe signal, similar to that of the NIST, and of the resonator resp... View full abstract»

Phase noise measurements of an optoelectronic oscillator (OEO) at frequencies less than 10 Ha from the carrier (10.6 GHz) as well as the measured Allan variance are presented for the first time. The system has a measured single-side-band (SSB) phase-noise of -123 dB/Hz at 10 kHz from the carrier and a /spl sigma//sub y/(/spl tau/)=10/sup -10/ for an integration time between 1 and 10 seconds. The i... View full abstract»

Direct digital frequency synthesizers (DDS or DDFS) are widely used in modern communications and measurement devices. Their advantages are small size and power consumption together with excellent frequency stability, high frequency resolution, and short switching times. The difficulties are rather low output frequencies (500 MHz at the present state of the art) and a large set of the spurious sign... View full abstract»

A mixer cascaded with a low-pass filter is the basic piece of any communication receiver. The frequency and amplitude fluctuations of beat signals recorded at the output of the mixer plus filter set-up are investigated experimentally and explained on the basis of number theory in relation to the Riemann problem concerning the distribution of prime numbers. The frequency of the beat signal is obtai... View full abstract»

Estimation of an atomic clock's frequency stability, separate from its reference, is often done using a three-cornered hat procedure. A major requirement for the success of this method is that clocks be uncorrelated. If this requirement is not satisfied, the three-cornered hat procedure can lead to misleading or even negative variance estimates. Others have considered this problem and developed an... View full abstract»

This paper presents near infrared absorption measurements (in the region of 3100-3700 cm/sup -1/) on quartz crystals to characterize the aluminum- and alkali-related hydroxyl defects in a variety of natural and cultured quartz crystals. Quartz samples were irradiated with an electron beam of 1.75 MeV and a dose of 2 Mrad at 77 K before and after irradiation at 300 K. The alkalis in quartz move und... View full abstract»

A method to grow low dislocation density synthetic quartz by using a special cutting seed geometry is reported. With this method, a relatively high dislocation density seed material is allowable. For such a purpose, a seed of new geometry was prepared and grown in a standard hydrothermal growth condition, long in Y-direction with multiple V-shaped notches made on Z-face. The characterization study... View full abstract»

Simple microstructures such as mesa and membrane are micromachined on singly and doubly rotated quartz plates. A stereographic analysis of 3-D etching shapes is used to recognize rhombohedral faces limiting micromachined structures. An iterative procedure is used to adjust the database in which first we generate extrema in the dissolution slowness for these faces, and second, we compare step-by-st... View full abstract»

Lapping and polishing processes of natural quartz are investigated in relation to crystallographic orientation and applied normal stress. Weight loss measurements and surface profilometry were carried out in X-, Y-, Z-, and AT-cut samples. The relationship found between material removal rate and stress depends on specimen orientation. Based on indentation fracture mechanics, this behavior is discu... View full abstract»

The SAW waveguide technique was used to form a novel reflector-filter for the realization of compact IF filters in CDMA handsets. The reflector-filter design is an attractive technique to obtain characteristics with steep skirts in a short device length, because the SAW propagation path is folded and the frequency response is synthesized by utilizing both IDT and reflector responses. In this paper... View full abstract»

Theoretical studies on the behavior of leaky-SAW (LSAW) properties in layered structures were performed. For these calculations rotYX LiTaO/sub 3/ and rotYX LiNbO/sub 3/ LSAW crystal cuts were used, assuming different layer materials. For LSAWs both the velocity and the inherent loss due to bulk wave emission into the substrate are strongly influenced by distinct layer parameters. As a result, the... View full abstract»

An application specific integrated circuit for the pressure and temperature measurement at the high temperature oil well bottom conditions is presented in this paper. The circuit is mainly composed of three high performance automatic level controlled (ALC) oscillator circuits, which drive three external crystals (the sensitive elements), as well as mixing and filtering stages. The integrated circu... View full abstract»

Viscoelastic properties of chemically sensitive coatings can enhance the mass sensitivity of quartz-crystal-microbalance (QCM) sensors. If analyte sorption is accompanied by a change of the viscoelastic properties of the coating material, the accumulated mass cannot be calculated from the frequency shift without further information. We developed a sensor concept, which is based on a double-layer a... View full abstract»

The frequency stability of an atomic fountain clock can be limited by the phase noise of the interrogation oscillator via the "Dick effect." In this paper we demonstrate the rejection of the phase fluctuations of the interrogation oscillator by the synchronization of atomic fountains. A reduction by a factor of 16 in the Allan standard deviation of the relative frequency difference between two fou... View full abstract»