Showing papers on "Crystal oven published in 1994"

Fundamental limits on the frequency instabilities of quartz crystal oscillators

Abstract: The frequency instabilities of precision bulk acoustic wave (BAW) quartz crystal oscillators, and the contributions from the instabilities of resonators, sustaining circuits, and ovens, are reviewed. The fundamental limits on the achievable frequency stabilities, and the degree to which the fundamental limits have been approached to date are examined. Included are the instabilities as a function of time, temperature, acceleration, ionizing radiation, electromagnetic fields, humidity, atmospheric pressure, power supply and load impedance. Most of the fundamental limits are zero or negligibly small, a few are finite. The authors speculate about the progress which may be achievable in the future with respect to approaching the fundamental limits. Suggestions are provided about the paths that may lead to significant stability improvements. >

A microprocessor-based analog wristwatch chip with 3 seconds/year accuracy

Abstract: Previous developments on a 2.1MHz quartz have demonstrated that thermal, ageing and shock performances are improved by at least one order of magnitude compared to a 32kHz quartz. The temperature behavior is a flat cubic function, and therefore positive and negative deviations with respect to the reference temperature are compensated. A field test on 20 watch samples containing an oscillator built around this quartz showed that over a 3-year period, the maximum deviation is less than 3 seconds/year. Note that these results are obtained without any temperature compensation scheme. As the power consumption of a 2.1 MHz quartz oscillator (2.3/spl mu/A) is not compatible with the power consumption of standard watch oscillator circuits ( >

Dual-mode crystal oscillators with resonators excited on B and C modes

Abstract: There is very attractive idea to use SC-cut resonators excited on B and C modes for frequency stabilization (in particular, for digital thermocompensation) but up to now these operating regimes are used very seldom. The cause consists in a difficulty to get stable excitation in wide temperature range. Due to development of original resonator excitation networks, of special geometry of piezoelement and due to original technology of its manufacture, we succeeded in developing of B and C modes in wide (-60...+85)/spl deg/C temperature range. 70% yield of suitable units is attainable when resonators are exited on 10 MHz frequency using 1st mechanical harmonic. The requirements to a circuit of a dual-mode oscillator (that is oscillator capable of simultaneous exiting on two asynchronous frequencies) are presented. A lot of experiments have been involved to design double-mode crystal meeting the requirements assigned above. To avoid the dips of activity of the B-mode being inherent property of overton SC-cut crystals due to nonlinear interaction of the thickness modes the fundamental mode TD-cut (yxb1/23/spl deg/25'/34/spl deg/) crystal plate has been used here. Exploration of the modes activity behavior over a wide temperature range has shown that the motional resistance remains within (8-12) Ohms for C-mode and (50-65) Ohms for B-mode. Practical realization of the dual-modes oscillator in the form of a hybrid LCI is described. The dual-mode crystal oscillator parameters are: output frequency 10 MHz; supply voltage 5V; consumption current 5-7 mA; output levels TTL. >

One-chip quartz crystal oscillator using a direct-bonding technique of quartz crystal onto silicon

Abstract: A one-chip quartz crystal oscillator (XO) using a novel fabrication method to bond directly quartz crystal onto silicon (QOS) without any adhesive, is reported together with its fabrication process, microstructure of the bonded interface, and electro-acoustic characteristics

Method for updating temperature versus frequency characteristic data for oscillator

Abstract: PURPOSE: To compensate secular change in an oscillation frequency from a crystal oscillator digitally. CONSTITUTION: Oscillation frequency signal from a crystal oscillator 10 is counted by a frequency counter 26 based on a clock from a satellite positioning device 12 and obtained frequency data are stored in an EEPROM 24 together with temperature data obtained by a temperature sensor 28. The temperature versus frequency characteristic of the crystal oscillator 10 is obtained based on data stored in the EEPROM 24 and the temperature versus frequency characteristic having been stored in the EEPROM 24 as a table are updated by new temperature versus frequency characteristic data prior to shipment. Since the new temperature versus frequency characteristic data reflects on the secular change in the oscillated frequency signal from the crystal oscillator 10, a system reference frequency obtained by a PLL 14 is controlled accurately to an object frequency independently of secular change by setting a frequency division ratio of a frequency divider 22 based on the temperature versus frequency characteristic data. COPYRIGHT: (C)1995,JPO

A Low Power, Frequency-Trimmable, Crystal Oscillator

Abstract: A high-precision auto-regulated low-power crystal oscillator is presented. A bank of capacitors is used to compensate initial accuracy and temperature deviation of the quartz. A novel structure for the output buffer is presented. Low power consumption and small chip size are obtained with an 1.2 ?m BICMOS process.

Voltage controlled oscillator circuit for reducing the effects of vibration on quartz crystal oscillator

Abstract: An oscillating apparatus includes a quartz crystal oscillator for outputting a reference frequency signal, a phase-locked loop for oscillating a desired frequency signal on the basis of an output from the quartz crystal oscillator, a unit for detecting vibration components added to the quartz crystal oscillator, a unit for variably controlling phases and levels of the detected vibration components, a unit for obtaining a correlation value between the detected vibration components and vibration components in the phase-locked loop to variably control the phases and the levels, and a unit for controlling the phase-locked loop on the basis of the phases and levels of the vibration components which are variably controlled.

TCXOs employing NS-GT cut quartz crystal resonators for cellular telephones

Abstract: This paper describes temperature compensated crystal oscillators (TCXOs) employing new shape GT cut quartz crystal resonators (NS-GT cut resonators) to be used in cellular telephones. The NS-GT-TCXO has an oscillation frequency of 2.4 MHz and a frequency stability of /spl plusmn/1.5 ppm within a temperature range of -20/spl deg/C to +70/spl deg/C using a simplified temperature compensation method. These superior characteristics can be achieved with low current consumption (approximately 0.8 mA) and compactness (11.5 mm/spl times/8 mm/spl times/4 mm). Additionally, the phase-noise characteristics of the NS-GT-TCXO have been evaluated. The phase-noise value of the phase-locked loop circuit using the NS-GT-TCXO as a reference oscillator is approximately -70 dBc/Hz at 50 Hz offset from the 614.4 MHz carrier. This meets the requirements for use in cellular telephones. These results indicate that the miniaturization and low power consumption of the NS-GT-TCXO could have an important impact on the development of future cellular telephone systems. >

Soft-transition FSK dimmer for gaseous luminous tube lights

Abstract: A dimmer oscillator for a high frequency luminous tube power supply including a frequency shiftable high frequency oscillator, a variable duty cycle low frequency oscillator operatively connected to the high frequency oscillator for controlling the high frequency oscillator between a first normal output operating frequency and a second higher frequency. A low pass filter within the high frequency supply whereby the supply output to a luminous tube load is reduced, when the oscillator is operating at the second higher frequency, to a low intensity ionization maintenance level. An integrator between the low and high frequency oscillators whereby the transition between the first nominal and second higher operating frequencies is smoothed to reduce acoustic noise and false GFI and OVP triggering. A frequency control diode between the low and high frequency oscillators to limit the lower frequency excursion, and to maintain oscillation of, the high frequency oscillator.

Application of LFE SC-cut resonators at high stability oscillators

Abstract: The LFE SC-cut resonators have some quite well known advantages. The main are: lack of electrodes in the active part of the crystal plate and very efficient suppression of B mode. Because of this application of LFE resonators can improve both long and short term frequency stability, critical for high stability oscillators parameters. A few models of different construction single side resonators were made and their parameters were measured. These resonators are very difficult to adjust (because of very low C1) so the special procedure of calibration using chemical treatment was developed. The especially optimized oscillation circuit was applied. Circuits and oven parameters were measured and discussed. >

Temperature‐compensated crystal oscillator using a two‐port crystal resonator

Abstract: In general, the oscillation frequency of a quartz crystal oscillator is shifted by varying the load capacitance of the quartz crystal resonator. Since the relation between load capacitance and oscillation frequency of the crystal resonator is nonlinear, the rate of change of frequency is slightly different from the load capacitance before and after the frequency shift. When the variation of oscillation frequency due to aging is compensated using the temperature-compensated crystal oscillator (TCXO) or the voltage-controlled temperature-compensated crystal oscillator (VCTCXO) or the oscillation frequency is shifted, the frequency compensation amount set by the temperature compensation circuit is different before and after the compensation. Thus, the frequency versus temperature characteristics vary. To solve this problem, the author has developed a special quartz crystal resonator with two-port electrodes. Since this crystal resonator has two load capacitances, the compensation of the temperature characteristics and the shift of oscillation frequency can be conducted independently. Thus, the problem of the changes in the temperature characteristics due to the oscillation frequency shift of a TCXO has been solved. This problem could not be solved using the conventional quartz crystal oscillator having only one capacitance. In this paper, measurement is made under the condition that the oscillation frequency of the TCXO using a two-port crystal resonator is shifted by ± 15 ppm and the performance is compared with that of TCXO using a conventional crystal resonator. the measurement has revealed that the change of frequency versus temperature characteristics is extremely small when the oscillation frequency of the TCXO using a two-port crystal resonator is shifted.

Quartz oscillator arrangement

Abstract: of EP0372646To stabilise the frequency emitted by a crystal oscillator, a first crystal of a crystal oscillator is operated at the turn-over point of its temperature/frequency characteristic and kept at constant temperature in a thermostatic housing. The thermostatic housing contains a second temperature-dependent crystal of an auxiliary oscillator which regulates the heating of the thermostatic housing. It is proposed that the thermostatic housing is constructed to be symmetrical and exhibits two chambers for accommodating the crystals of the crystal oscillator and of the auxiliary oscillator, the frequency of the auxiliary oscillator corresponding to the frequency of the crystal oscillator. The crystals of the crystal oscillator and of the auxiliary oscillator are provided with crystal housings which are in each case identical. Clock supply devices for communications engineering.