Proceedings of the 2005 IEEE International Frequency Control Symposium and Exposition, 2005.

An overview on the use of microelectromechanical systems (MEMS) technologies for timing and frequency control is presented. In particular, micromechanical RF filters and reference oscillators based on recently demonstrated vibrating on-chip micromechanical resonators with Q's >10,000 at 1.5 GHz, are described as an attractive solution to the increasing count of RF components (e.g., filters) expect... View full abstract»

The U.S. Naval Research Laboratory (NRL) has collected data and analyzed GPS space vehicle atomic clock performance since the beginning of the GPS Program. These analyses have largely been based on pseudorange observations and precise post-fit ephemerides provided by the National Geospatial-Intelligence Agency (NGA). Observational data and clock comparisons were limited to data collected within th... View full abstract»

ITT Industries developed GPS IIR satellite payloads have been on-orbit since July of 1997, providing outstanding signal-in-space performance. Much of the credit for this outstanding performance can be given to the GPS IIR time keeping system (TKS). A key component of the TKS system is Perkin Elmer's rubidium atomic frequency standard (RAFS). We now have over 40 years of on-orbit experience with th... View full abstract»

Galileo program is approved by the European Commission and the European Space Agency (ESA). The activities related to GSTBV2 experimental satellite as well as the implementation of the in orbit validation phase are in progress. Atomic clocks represent critical equipment for the satellite navigation system and clocks development has been continuously supported by ESA. The rubidium atomic frequency ... View full abstract»

Precise timing is an inherent part of Global Navigation Satellite Systems (GNSS) like GPS, Glonass and in the future Galileo. In the framework of the interoperability and compatibility discussions between the United States and European Union it was agreed that both GPS and Galileo systems will compute and broadcast the mutual time offset between both system's time scales. This information once ava... View full abstract»

Time jitter is an important parameter for determining the performance of digital systems. This paper reviews how time jitter impacts the performance of digital systems. For the purposes of later discussions, digital systems are broken down into three major categories: synchronous data transfer, asynchronous data transfer, and digital sampling systems. A statistical framework is first developed for... View full abstract»

A frequency counter measures the input frequency nu averaged over a suitable time tau, versus the reference clock. Beside clock interpolation, modern counters improve the resolution by averaging multiple measurements highly overlapped. In the presence of white noise, the overlapping technique improves the square uncertainty from sigma nu 2 prop1/tau2 to sigman... View full abstract»

This paper presents the theoretical basis for an algorithm that performs an exact analysis of the output spectrum of direct digital frequency synthesizers (DDS or DDFS) in the presence of phase accumulator truncation, finite arithmetic precision and arbitrary approximations and errors in the sine/cosine mapping function (SCMF). The derivation provides strong insight into spurious frequency (spur) ... View full abstract»

Following successful application in gas sensing, acoustic wave liquid sensors attracted considerable attention due to the need for real-time, rapid and direct detection where the device is in direct contact with the solution. More importantly, there is a need for field measurement capability with portable devices. Challenges include a physical layout of the RF circuitry to minimize parasitic and s... View full abstract»

The adsorption of copper and lead on MnO2 was followed by monitoring the frequency of piezoelectric crystal coated with MnO2 in contact with solutions of the metal under study, at controlled temperature. Each isotherm was constructed for concentrations of each metal between 1 and 58 mg L-1. When absorption data for copper or lead were fitted to the Langmuir isother... View full abstract»

In this paper, we present two types of high-frequency bulk acoustic resonant microbalances based on (1) film bulk acoustic resonator (FBAR) and (2) high-tone bulk acoustic resonator (HBAR). Both resonators are operating at about 900 MHz, hundred times higher than a typical quartz crystal microbalance (QCM). Mass sensitivities of the FBAR and HBAR microbalances are measured to be 782.7 (50 times la... View full abstract»

Recent progress in nanotechnology has lead to development of novel materials with very unique superhydrophobic (SH) properties. In this paper, we study the thickness-shear mode (TSM) sensing technique as a potential measurement tool for characterization of SH properties of materials. The TSM sensors, coated with different SH thin films were capable to differentiate between a range of the SH proper... View full abstract»

This paper describes the use of a temperature-compensation circuits for simple solution-concentration sensor with temperature compensation using bulk acoustic waves. We analyzed the design method of temperature-compensation circuit (TCC) in order to eliminate considerable effect temperature has on sound velocity in liquids. The design methods are derived on a temperature-compensation factor by usi... View full abstract»

We present a comparison between SYRTE's Cs fountain FO1 and Cs-Rb fountain FO2 using a cryogenic sapphire oscillator (CSO) to generate an ultra-stable interrogation signal. A description of the experimental setup is given and the clock accuracies are discussed. For the first time, a frequency resolution in the low 10-16 is achieved in the comparison between two primary standards. The pa... View full abstract»

We discuss the power dependence of distributed cavity phase errors for cylindrical TE011 cavities in laser-cooled atomic fountain clocks. The azimuthally symmetric phase variations produce a surprisingly large distributed cavity phase error for two 2pi, 4pi, and 6pi pulses. This is due to the correlation between the transverse variation of the Rabi frequency over the cavity aperture and... View full abstract»

We show that the frequency bias caused by distributed cavity phase has a strong dependence on microwave power. We also show that frequency biases associated with microwave leakage have distinct signatures in their dependence on microwave power and the physical location of the leakage interaction with the atom. View full abstract»

The HORACE device is a compact cold atom clock where about 108 cesium atoms are laser cooled at a few μK, then interrogated and detected directly in a 20 cm3 spherical microwave cavity. The optimization of the short term stability with the cooling and interrogation durations is presented, leading to an estimation of the Allan deviation of σy(τ) -1 10 View full abstract»

Lorentz invariance (LI) is the founding postulate of Einstein's 1905 theory of relativity, and therefore at the heart of all accepted theories of physics. It characterizes the invariance of the laws of physics in inertial frames under changes of velocity or orientation. This central role, and indications from unification theories (Kostelecky, 1989) hinting toward a possible LI violation, have moti... View full abstract»