Showing papers on "Crystal oven published in 2000"

A digitally temperature-compensated crystal oscillator

Abstract: The base frequency of oscillators used in the Global System for Mobile Communication (GSM) network or Global Positioning System (GPS) receiver applications needs to be very stable with respect to temperature and supply-voltage variations. One approach to obtain extremely good frequency stability is the use of oven-stabilized crystal oscillators. With this kind of oscillator, a frequency stability versus temperature of a few ppb versus the standard temperature range can be achieved. In this paper, a digitally compensated crystal oscillator is described. The system provides a frequency stability of (/spl Delta/f)/f<1.5 ppm for a temperature range of -40/spl deg/C to 90/spl deg/C compared to about /spl plusmn/20 ppm for a noncompensated crystal. The core of the system is an application-specified integrated circuit (ASIC) fabricated in a standard 0.8-/spl mu/m CMOS process. The power consumption for the oscillator running at 13 MHz is 100 mW. The final device equipped with the ASIC, crystal blank, and a few external components fits into a 14/spl times/9/spl times/3 mm/sup 3/ package.

Temperature controlled compensated oscillator

Abstract: A temperature compensated crystal oscillator using an AT cut crystal produces a reference frequency. The temperature compensated crystal oscillator is located inside a temperature controlled oven. The temperature controlled oven provides a stable temperature to the temperature compensated crystal oscillator such that deviations from the reference frequency are reduced.

Oscillator circuit configuration for quartz-crystal-resonator sensors subject to heavy acoustic load

Abstract: An oscillator circuit configuration is presented to track accurately the resonant frequency and to increase the operating range of quartz-crystal-resonator sensors subject to heavy acoustic loading. The circuit is based on a block for the active cancellation of the crystal electrical capacitance, inserted in a phase-locked loop oscillator. Experimental results confirming the successful application of the principle are reported.

Crystal oscillator with frequency trim

Abstract: A timing crystal oscillator circuit that may be tuned after production. The circuit generally comprises a microprocessor configured to present one or more control signals, one or more load devices that may be activated in response to the control signals and a crystal oscillator for presenting an output signal having a frequency which is generally dependent on the number of load devices activated.

Method and apparatus for characterizing and adjusting a crystal oscillator for use in a spread spectrum, frequency hopping transceiver

Abstract: An economical, compact frequency hopping spread spectrum wireless data telemetry transceiver is adapted to establish and maintain communication links at 2.4 GHZ. The wireless transceiver includes RF and computer control components in a compact package approximately the size of a deck of cards and is adapted to be built into original equipment manufacturer (OEM) products to support a wide range of wireless data telemetry applications. The transceiver includes an inexpensive VCO which is controlled by novel method including steps to characterize and adjust the frequency output of the crystal. As ambient temperature around a quartz crystal varies, the resonant frequency of the crystal varies, in different ways, depending on the method used to cut the crystal from a quartz blank. Employing a quartz crystal in an oscillator circuit to generate a reference frequency subjects the oscillator to the same frequency variations over temperature as the quartz crystal. In accordance with the present invention, a temperature sensor constantly outputs a signal proportional to the temperature of the crystal in the oscillator. A micro-controller initiates a conversion via the analog to digital converter (ADC) and the micro-controller then uses the ADC output signal to look up an adjustment number in a pre-programmed lookup table; the adjustment number is input to the digital to analog converter, which then performs a conversion to output a DC voltage to the VCO, adjusting the frequency of the oscillator to the desired reference frequency, thus effectively providing an open loop VCO control system.

Liquid crystal panel driving method, liquid crystal device, and electronic apparatus

Abstract: A liquid crystal panel driving method is provided for optimizing driving conditions by performing temperature compensation without varying the voltage of a driving signal. In the liquid crystal device, based on a temperature detection result by the temperature sensor, a temperature compensating circuit sets the frame frequency of driving signals output from driving circuits to a liquid crystal panel at a low temperature, thereby performing temperature compensation so that the liquid crystal device is operated under a condition in which the dielectric anisotropy of the liquid crystal is substantially flat. In accordance with the fact that the motion of the liquid crystal molecules becomes active at a high temperature, the temperature compensating circuit sets the frame frequency of the driving signals to be high. Concerning the frame frequency, 50 Hz (or 60 Hz) and an integer multiple of that frequency are avoided.

Theory and design of crystal oscillators immune to acceleration: present state of the art

Abstract: Theoretical and experimental results on the acceleration sensitivity of quartz crystal oscillators were consolidated in Filler's benchmark review paper published in the May 1988 Special Issue on Frequency Control, Part II of the IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. Since that time, a large body of additional work has been produced. This paper reviews those developments from the perspective of oscillator design. Areas of direct interest for oscillator design include equivalent circuit models, oscillator circuit interactions, and vibration compensation techniques, along with a clear and concise summary of tile state-of-the-art in low acceleration sensitivity resonator design.

An ultra-miniature rubidium frequency standard

Abstract: An ultra-miniature, general-purpose rubidium gas cell frequency standard with a two-cell scheme has been successfully developed, with the aim of developing one of the smallest atomic frequency standards in the world. The target volume of the new rubidium frequency standard is less than 100 cm/sup 3/. It is assumed that the shape of oscillator enables to mount on a printed circuit board. In order to miniaturize the volume and height, the physics package is made small. Because the frequency of the cavity resonator is 6.834 GHz and the resonator mode is TE/sub 111/, the inside diameter of the cavity needs to be 26 mm. To reduce the inside diameter, a new cavity resonator, which contains a dielectric material, has been developed. As a result, an inside diameter of 16 mm and a capacity of 6.7 cm/sup 3/ are achieved. The total size of the physics package, which contains a rubidium-lamp exciter, a preamplifier, and a single magnetic shield of mumetal, is reduced to 25 cm/sup 3/. By applying the PLL method, instead of the conventional frequency multiplier for a high frequency circuit that generates resonance frequency of 6.834 GHz from a slave oscillator, the size and cost of the circuit are minimized. As for the reduction of the power consumption, a new switching regulator IC is adopted in the power circuit. In addition, with the use of DDS, it enables to set the output frequency within the range of 1 to 15 MHz. Because of these features, the new rubidium frequency standard is extremely small in volume (95 cm/sup 3/), and lightweight (180 grams).

Crystal oscillation circuit and crystal resonator

Abstract: PROBLEM TO BE SOLVED: To provide a crystal oscillation circuit and a crystal resonator where the frequency stability with high accuracy can surely be obtained without the need for detection of a temperature by a temperature sensor. SOLUTION: Two crystal resonators 7A, 7B thermally coupled are used, two crystal oscillation sections 8, 9 output oscillation signals with frequencies f1, f2, and a correction frequency difference δf denoting a difference between the frequency f1 due to a temperature change and an object output frequency f0 is obtained from a difference frequency Δf representing difference between the frequencies f1, f2. Then a frequency addition section 12 adds the correction frequency difference δf to the frequency f1 to obtain an output signal with the object frequency f0 stabilized against the temperature change without the need for detecting the temperature.

Analog ALC crystal oscillators for high-temperature applications

Abstract: Fundamental mode and third-harmonic mode integrated high-performance automatic level controlled (ALC) crystal oscillators for high-temperature applications (up to 250/spl deg/C), are described in this paper. These oscillators were designed for a pressure measurement system in high-temperature environments, where the output signal is the difference between both generated frequencies. Frequency variations smaller than 0.0001 ppm/s for each oscillator and a frequency drift of about 2.5 ppm/year of the frequency difference are the measured performance concerning, respectively, the short-term (1 s) and long-term frequency stability of these integrated high performance crystal oscillators over the 30/spl deg/C-225/spl deg/C temperature range. Other important characteristics are the very stable and constant oscillation levels (/spl sim/1.1 Vpp), the small second-harmonic distortion (/spl sim/60 dR), and the phase noise (/spl sim/95 dB at 50 kHz shift). The characteristics of these oscillators make them also suitable for many other measurement systems (time, temperature, and other physical and chemical quantities), especially if they are constrained to operate under severe temperature conditions.

Software controlled crystal oscillator

Abstract: A software controlled crystal oscillator employing a method for digitally controlling a reference frequency of an oscillator, the method includes the steps of: locking a first signal produced by a first tunable software oscillator on to a first resonant frequency of a temperature sensing resonator; locking a second signal produced by a second tunable software oscillator on to a second resonant frequency of the temperature sensing resonator; estimating a temperature of the temperature sensing resonator using the first signal and the second signal; estimating the first resonant frequency and the second resonant frequency based upon the temperature; and adjusting the first signal to approximate the estimated first resonant frequency. An additional step includes controlling the reference frequency of the oscillator based upon the first signal such that the reference frequency is compensated for temperature.

Properties of AT cut gallium phosphate resonators

Abstract: Gallium orthophosphate is a quartz-homeotypic piezoelectric crystal that presents simultaneously a much larger coupling coefficient (k/sup 2/ is nearly four times that of quartz) and a large thermal stability of its properties. Previous experiments and calculations have shown that the main singly rotated compensated cut (the equivalent of the AT cut of quartz) is situated near Y-15/spl deg/ 45'. It was also shown that the devices made using this material should present several advantages over quartz for filter or oscillator applications. Several new determinations of the material constants were made in recent years. They allow to predict more accurately the properties of devices. More recently several new advances in crystal growth have led to an important increase in the size of the crystals and of the crystalline quality. In order to precise determine the properties of devices made with orientations near the AT cut, new investigations were made. In this contribution we report the most important features observed during these experiments.

A new type of balanced-bridge controlled oscillator

Abstract: A novel bridge-controlled crystal oscillator circuit with exceptional temperature stability is described. The contribution to the oscillator temperature coefficient of frequency (tempco) from the circuit components (exclusive of the crystal) is reduced to about 10/sup -11///spl deg/C, which is several orders of magnitude better than conventional oscillator circuits. This avoids a situation in which the overall tempco is limited by circuit component drift rather than crystal stability, which can easily occur with conventional circuits when the crystal is ovenized at a turnover point. Previous attempts to use a bridge in an oscillator were made by Meacham (1938), who used an imperfectly balanced bridge, and Sulzer (1955), who used a balanced pseudo-bridge. The reasons why these are unsatisfactory are discussed. Although the bridge greatly reduces reactive frequency pulling, it does not address directly the additional issue of pulling caused by variations in crystal drive current amplitude. However, it is an enabling technology for a novel ALC circuit with greatly improved stability. The new bridge-controlled oscillator is also much less sensitive to other environmental effects such as humidity (2/spl times/10/sup -11/, 5%/25% R.H. @70/spl deg/C), power supply voltage, load impedance, and stray capacitance.

Laser controlled crystal and dielectric resonator oscillators

Abstract: A crystal oscillator including a laser light source for emitting a laser beam to an aligned quartz crystal coupled to an oscillator circuit by an optical feedback network. The optical feedback network is responsive to variations of misalignment of the laser beam with the crystal and correction signals generated for introduction back to the crystal to bring its frequency back to a constant standard frequency output.

Nonlinear dependencies and phase noise in precision crystal oscillator

Abstract: A quantitative estimation of the influence of an active device operational mode on the phase fluctuations in precision voltage controlled crystal oscillator at frequency range 100 MHz had been made. The relations between the coefficient of amplitude to phase noise conversion and the ratio of the device linear mode realm to the non-linear mode realm are evaluated. The recommendations obtained with the help of numerical analysis have allowed us to optimize operation of the precision voltage controlled crystal quartz oscillator, and to obtain short-term frequency stability close to the stability of a non-controlled oscillator.

Apparatus and method for changing crystal oscillator frequency

Abstract: A programmable capacitor array is used to trim the frequency of a crystal oscillator for initial offset. An apparatus includes the crystal oscillator and an integrated circuit (36) is coupled to the crystal (30) of the oscillator. The programmable capacitor array (32) is formed on the integrated circuit and is coupled to the crystal (30) and is responsive to a signal for setting the capacitance of the capacitor array to one of a number of capacitance values. A discrete controllable capacitance device (V03) not one the integrated circuit is coupled to the crystal (30) and is responsive to a control signal (AFC) to change its capacitance. The crystal oscillator frequency is dependent on the capacitances of both the programmable capacitor array (32) and the discrete capacitor (V03).

Ultra-stable OCXO using dual-mode crystal oscillator

Abstract: A high-stability oven controlled crystal oscillator (OCXO) (frequency stability; /spl plusmn/0.5 ppb from -10 to +50/spl deg/C) has been developed using a dual-mode SC-cut quartz crystal oscillator. The OCXO described here uses a conventional oven control system for coarse compensation and a digital correction system, which uses B-mode signals as a temperature sensor, for fine compensation. These compensations combine to greatly improve the C-mode frequency stability when the ambient temperature changes. The experimental results indicated that the proposed OCXO had a frequency-temperature stability 60 times better than that of a free-running mode oscillator.

High frequency oscillation circuit

Abstract: A high-frequency oscillation circuit incorporates a crystal oscillator having a natural oscillation frequency in a high-frequency area within a closed circuit including one or more logic elements. Therefore, this circuit copes with an oscillation frequency of 1 MHz to 2 GHz or more in basic oscillation frequency of a crystal oscillator and it oscillates with stability at the basic oscillation frequency of the crystal oscillator.

Characterization of quartz crystal resonators on phase modulation noise without an oscillator

Abstract: In the time domain, two methods are investigated to classify the phase noise of the resonators. A numerical model of frequency stability of ultra stable quartz oscillator is used to obtain the power spectral density of the phase fluctuations of an oscillator which contains the test resonator. The measurements of the phase noise of the quartz crystal resonators are obtained with a crystal resonator tester. New LD-cut 10 MHz BVA quartz crystal resonators are investigated.

2000 IEEEIEIA International Frequency Control Symposium and Exhibition ULTRA-STABLE OCXO USING DUAL-MODE CRYSTAL OSCILLATOR

Abstract: A high-stability oven controlled crystal oscillator (OCXO) (frequency stability; f 0.5 ppb from -10 to +50 "C) has been developed using a dual-mode SC-cut quartz crystal oscillator. The OCXO described here uses a conventional oven control system for coarse compensation and a digital correction system, which uses B-mode signals as a temperature sensor, for fine compensation. These compensations combine to greatly improve the C-mode frequency stability when the ambient temperature changes. The experimental results indicated that the proposed OCXO had a frequency-temperature stability 60 times better than that of a free-running mode oscillator.

Various ways to temperature-regulate an ultrastable quartz oscillator

Abstract: An ultrastable quartz crystal oscillator (USO) must obviously be ovenized. Frequency fluctuations partly come from static changes of the ambient temperature as well as dynamic ones. Both effects are detailed and their consequences on the oven design are discussed. The static frequency deviation is mainly related to the efficiency of the thermal regulator: for example, to achieve a relative frequency fluctuation a few 10/sup -10/ over an ambient temperature range of [-30/spl deg/C, +70/spl deg/C], the static thermal gain must reach at least 1000. However, a standard proportional and integral thermal controller which can eliminate the static error is unable to do this for the fast thermal disturbances. Here the thermal filtering must work in accordance with the cut-off frequency of the frequency-temperature transfer function of the quartz resonator. Various methods for controlling the oscillator temperature are presented: the usual method consists of using more than one temperature-controlled oven. This is often a volume-consuming process. An alternative approach, which is much simpler, is to add a "light" compensation effect to the feedback control system. A third way to improve the temperature regulation is based on distribution of the monitoring power. Obviously, a mix of those solutions is possible. Advantages and drawbacks of each of them are discussed. Practical results are shown and illustrated with 10 MHz USO devices.

A low profile quartz crystal resonator for OXCO in cellular telephone system

Abstract: We realized 15 mm-in-height quartz crystal resonator with aging characteristic of less than 2/spl times/10/sup -11//day and acceleration sensitivity of less than 1/spl times/10/sup -9//g. Large effort has been paid to the designing of the base structure. We designed the base as low as possible and at the same time, it should avoid the strain transmitting to the quartz plate caused by the coldweld sealing. The mounting angle was experimentally determined so that the acceleration sensitivity would be minimized. As a result, 4.5 mm-in-height quartz crystal resonator with excellent aging characteristic and small acceleration sensitivity was successfully realized.

2000 IEEEEIA International Frequency Control Symposium and Exhibition NOVEL TECHNIQUE FOR DUAL-MODE QUARTZ OSCILLATORS

Abstract: This paper describes a novel concept in designing of dual-mode quartz crystal oscillators that are widely used in sources with improved frequency stability. The suggested scheme incorporates a single feedback loop comprising a sustaining amplifier with a triangular amplitude characteristic loaded on a pass filter with two low-Q resonant frequencies followed by a quartz network. The feedback is positive for one used mode and negative for another. In result, the oscillator is capable to provide essentially different harmonics as two simultaneous oscillations can occur only when a magnitude of the chosen ccpositive)) mode becomes high enough.

2000 IEEEIEIA International Frequency Control Symposium and Exhibition CHARACTERIZATION OF QUARTZ CRYSTAL RESONATORS ON PHASE MODULATION NOISE WITHOUT AN OSCILLATOR

Abstract: In the time domain, two methods are investigated to classify the phase noise of the resonators. A numerical model of frequency stability of ultra stable quartz oscillator is used to obtain the power spectral density of the phase fluctuations of an oscillator which contains the test resonator. The measurements of the phase noise of the quartz crystal resonators are obtained with a crystal resonator tester. New LD-cut 10 MHZ BVA quartz crystal resonators are investigated. From the measured %&f) of the quartz crystal resonator pairs, obtained by these previous techniques, several interpretations are possible in the time domain. In this paper, two methods are investigated to classify the phase noise of the resonators. The first one, gives a oY(z) of an oscillator containing the test resonator and the second one, gives the oY(z) of the resonator submitted to perfect sinus wave. Comparison of these approaches and a numerical model of frequency stability of ultra stable quartz oscillator is given. This numerical model is used to evaluate the power spectral density (PSD) of the phase fluctuations of the oscillator containing the test resonator. A study of the phase noise in 10-MHz LD-cut BVA quartz crystal resonator pair is given. The measurements of the phase noise of the quartz crystal resonators are obtained with a crystal resonator tester specifically designed to assist in the characterization of quartz crystal resonators in the 1 to 200 MHz region (3). The measurement device allows to measure the inherent phase stability of quartz crystal resonators in a passive circuit without the noise usually associated with an active