Showing papers on "Crystal oven published in 2005"
TL;DR: In this article, a photonic delay line is used as a frequency discriminator for measurement of the phase noise of microwave oscillators, which is suitable for a wide range of frequency without reconfiguration.
Abstract: A photonic-delay line is used as a frequency discriminator for measurement of the phase noise - hence the short-term frequency stability - of microwave oscillators. The scheme is suitable for electronic and photonic oscillators, including the optoelectronic oscillator, mode lock lasers, and other types of rf and microwave pulsed optical sources. The approach is inherently suitable for a wide range of frequency without reconfiguration, which is important for the measurement of tunable oscillators. It is also insensitive to a moderate frequency drift without the need for phase locking.
108 citations
TL;DR: In this article, a comparative study of noise and resolution is presented with respect to the frequency and the quality factor of the microbalance oscillator for damping media, and it is shown that when working below the maximum quality factor, for similar values, the resolution can be improved by elevating the work frequency.
Abstract: The use of quartz-crystal oscillators as high-sensitivity microbalance sensors is limited by the frequency noise present in the circuit. To characterize the behavior of the sensors, it is not enough to determine their experimental sensitivity, but, rather, it is essential to study the frequency fluctuations in order to establish the sensor resolution. This is fundamental in the case of oscillators for damping media, because the level of noise rises due to the strong decline of the quality factor of the resonator. In this paper, a comparative study of noise and resolution is presented with respect to the frequency and the quality factor. The study has been made using four oscillators designed to be used in quartz-crystal microbalance sensors in damping media. The four circuits have been designed at increasing frequencies in order to improve the sensitivity or frequency change per unit of measurand. Also, the present theoretical resolution limit or best resolution achievable with a microbalance oscillator using an AT resonator is determined, since this does not depend on frequency. However, when operating in liquid, the damping of the resonator makes the resolution diminish due to a worsening of the quality factor. The relationship between the resolution limit and the frequency and characteristics of the liquid medium is determined. The resolution worsens when the density and viscosity of the liquid is increased. However, in this case, an increase in frequency implies a small increase in resolution. Therefore, we find that when working below the maximum quality factor, for similar values, the resolution can be improved by elevating the work frequency.
92 citations
Abstract: In this article, we describe a new frequency synthesis system that includes a low phase noise cryogenic sapphire oscillator (CSO) and an H-maser to provide metrological low-noise signals to time and frequency experiments. Implementing this system as a local oscillator for a Cs cold atom fountain, a record frequency stability of 1.6×10−14τ−1∕2 is obtained.
76 citations
Patent•
31 Mar 2005TL;DR: In this paper, an apparatus and method for calibrating a non-crystal oscillator in a transceiver unit using a crystal-oscillator includes the step of establishing a time base based upon oscillations of the crystal oscillator.
Abstract: An apparatus and method for calibrating a non-crystal oscillator in a transceiver unit using a crystal-oscillator includes the step of establishing a time base based upon oscillations of the crystal oscillator. A comparison of the number of oscillations for the non-crystal oscillator and the crystal oscillator is made during a known time period is made. An adjustment is determined based upon the established time base and the compared number of oscillations. The transceiving of the transceiver unit is then controlled based upon this adjustment.
56 citations
TL;DR: The experimental compensating results show that, using this method, the frequency-temperature stability of a 100 MHz 5th overtone temperature-compensated crystal oscillator can achieve < or = +/-2 x 10(-6) for 0-70 degrees C.
Abstract: In this paper, a novel microcomputer temperature-compensating method for an overtone crystal oscillator (MCOXO) is presented. In this method, a ceramic oscillator is chosen, and its output frequency is mixed with the output frequency of an overtone crystal oscillator. A crystal filter is used to suppress the spurious mixing products. A microcomputer is used to control the switch capacitance array that is connected to the ceramic oscillator circuit. The frequency deviation of the crystal oscillator is directly compensated by the output frequency of the ceramic oscillator. As a result, the method is able to overcome the disadvantages of frequency stability degradation and phase noise deterioration that are provoked by adding inductance or frequency multiplication in traditional compensating approaches. At the same time, this method is able to compensate a quite wide frequency range and many types of oscillators, not just crystal oscillators. The experimental compensating results show that, using this method, the frequency-temperature stability of a 100 MHz 5th overtone temperature-compensated crystal oscillator can achieve /spl les/ /spl plusmn/2/spl times/10/sup -6/ for 0-70/spl deg/C.
23 citations
Patent•
12 Jul 2005
TL;DR: In this article, the authors proposed a method to reduce the effects of temperature variations on an operating frequency of the temperature controlled frequency source by temperature compensating the temperature controlling frequency source.
Abstract: A method provides a temperature controlled frequency source. The method reduces the effects of temperature variations on an operating frequency of the temperature controlled frequency source by temperature compensating the temperature controlled frequency source.
22 citations
Patent•
29 Dec 2005TL;DR: In this paper, a first oscillator made from piezoelectric material was used to oscillate at a first frequency and a second oscillator was used at a second frequency, with a comparator to compare the first frequency to the second frequency.
Abstract: An apparatus, comprising: a first oscillator made from piezoelectric material to oscillate at a first frequency; a second oscillator to oscillate at a second frequency; a comparator to compare the first frequency to the second frequency; and a controller to change the first frequency in response to the comparing of the first frequency to the second frequency.
20 citations
Patent•
31 Mar 2005
TL;DR: In this paper, an oscillator and a method for producing an improved oscillator that will generate an accurate frequency when encountering a vibration was presented. But the oscillator was not used to measure any vibration and the method used a crystal with minimal cross-axis coupling.
Abstract: An oscillator and a method for producing an improved oscillator that will generate an accurate frequency when encountering a vibration. The oscillator and method uses a crystal with minimal cross-axis coupling. Further, a first accelerometer produced using MEMS technology is used. The first accelerometer is positioned inside of the oscillator so that the accelerometer accurately measures any vibration encountered by the oscillator. The first accelerometer and the crystal are maintained at constant temperature to minimize phase shifts and gain variations.
16 citations
TL;DR: In this article, an enhanced phase-noise model has been built to predict the phase noise in crystal oscillators, where the power spectral densities of phase fluctuations can be computed in different points of the oscillator loop.
Abstract: In order to predict the phase noise in crystal oscillators an enhanced phase-noise model has been built. With this model, the power spectral densities of phase fluctuations can be computed in different points of the oscillator loop. They are calculated from their correlation functions. The resonator-caused noise as well as the amplifier-caused noise are taken into account and distinguished. To validate this enhanced model, the behavior of a batch of 10 MHz quartz crystal oscillators is observed and analyzed. The tested batch has been chosen in a facility production. Their associated resonators have been selected according to the value of their resonant frequency and their motional resistance. Open-loop and closed-loop measurements are given. The phase noise of the overall oscillator working in closed loop is provided by the usual active method. Theoretical and experimental results are compared and discussed
15 citations
TL;DR: In this paper, a force sensor based on a quartz crystal was used for measuring nanoscale topographic images, which is a length-extensional mode oscillator with a resonant frequency of about 650 kHz.
Abstract: We report a force sensor based on a quartz crystal that is used for measuring nanoscale topographic images. The crystal is a length-extensional mode oscillator with a resonant frequency of about 650 kHz. Compared to 33 kHz tuning forks, such crystal sensors have a much higher resonance frequency, which allows for high force sensitivity and a fast response time. The crystal sensor is operated in the shear-force mode, with the probes vibrating parallel to the sample surface. The tip-sample interaction during operation is estimated to be less than 300 pN.
13 citations
Patent•
07 Mar 2005TL;DR: In this article, a mobile device includes frequency synthesizer circuitry (44) for generating a channel frequency at a multiple of a reference frequency, which is compensated by adjusting the multiplication factor of the synthesizer.
Abstract: A mobile device includes frequency synthesizer circuitry (44) for generating a channel frequency at a multiple of a reference frequency. The reference frequency is generated by a free-running crystal oscillator (72), without frequency stabilization circuitry. Variations in the output of the crystal oscillator (72) are compensated by adjusting the multiplication factor of the frequency synthesizer.
TL;DR: In this paper, a microwave local oscillator for a cesium atomic frequency standard was implemented using an ultra-stable oscillator based on a high Q-factor cryogenic-sapphire-resonator cooled with liquid helium which operates on Whispering gallery mode.
Abstract: A synthesized microwave local oscillator for a cesium atomic frequency standard has been implemented using an ultra-stable oscillator. The oscillator was based on a high Q-factor cryogenic-sapphire-resonator cooled with liquid helium which operates on a Whispering Gallery mode. The cesium hyperfine transition frequency of 9.192 GHz was synthesized from the 10.812 GHz oscillation frequency, chosen because the corresponding mode had the best frequency stability. When compared with a hydrogen maser reference the local oscillator exhibited a fractional frequency stability of 6×10-15 for integration times of 600 to 1200 s at 9.192 GHz, limited only by the cryogenic sapphire oscillator.
Patent•
16 May 2005
TL;DR: In this article, the use of an electrical pulse that is a single square wave to excite a piezoelectric crystal is described, which provides a significant increase in net drive power to the crystal without the need to provide a sine wave excitation of plus and minus voltage.
Abstract: The invention describes the use of an electrical pulse that is a single square wave to excite a piezoelectric crystal. This pulse is applied alternately to either side of the crystal at twice the nominal resonant frequency of the crystal. This method provides a significant increase in net drive power to the crystal without the need to provide a sine wave excitation of plus and minus voltage to the crystal.
Patent•
16 May 2005
TL;DR: In this paper, the use of an electrical pulse that is a single square wave to excite a piezoelectric crystal is described, which provides a significant increase in net drive power to the crystal without the need to provide a sine wave excitation of plus and minus voltage.
Abstract: The invention describes the use of an electrical pulse that is a single square wave to excite a piezoelectric crystal. This pulse is applied alternately to either side of the crystal at twice the nominal resonant frequency of the crystal. This method provides a significant increase in net drive power to the crystal without the need to provide a sine wave excitation of plus and minus voltage to the crystal.
31 Aug 2005
TL;DR: In this paper, a frequency stability analysis of a room temperature frequency-temperature compensated dual-mode resonator oscillator (patent pending) was performed using a single crystal cylindrical sapphire resonator, 40 mm in diameter and 20 mm high.
Abstract: A frequency stability analysis of a room temperature frequency-temperature compensated dual-mode resonator oscillator (patent pending) is presented. Using a single crystal cylindrical sapphire resonator, 40 mm in diameter and 20 mm high, two orthogonally polarized whispering gallery modes were simultaneously excited, with the difference frequency temperature dependence annulled near 304 K. The standard Allan deviation of the 3.39 GHz beat between the two modes was measured to be approximately 8 /spl times/ 10/sup -12/ between 1 and 4s.
01 Aug 2005
TL;DR: In this article, the frequency stability link between the optical and microwave frequencies in the coupled oscillator was investigated, and the phase-noise measurements of photonic microwave oscillators were described.
Abstract: In this paper, we will describe our recent phase-noise measurements of photonic microwave oscillators. We will aslo discuss our investigation of the frequency stability link between the optical and microwave frequencies in the coupled oscillator.