Showing papers on "Crystal oven published in 1991"

Digital temperature-compensated oscillator

Abstract: A digital temperature-compensated oscillator comprises a crystal oscillator, a first memory previously storing digital temperature compensation data obtained by previously measuring the relation between the ambient temperatures and the frequency deviations of the crystal oscillator, a second memory for storing frequency offset amounts of the oscillation frequency of the crystal oscillator, a temperature sensor for outputting analog detection data relating to the ambient temperature, an A/D converter for converting the analog detection data to digital detection data, a readout circuit for reading out temperature compensation data corresponding to the digital detection data and stored in the first memory according to the digital detection data and reading out the frequency offset amount stored in the second memory according to the digital detection data, an operation circuit for effecting the following calculation by use of the readout temperature compensation data and readout frequency offset amount to derive digital control voltage, V.sub.c =V.sub.co +(K.sub.00 +V.sub.co K.sub.10 +K.sub.01 T)×(ΔF+ΔF 2 ×K 10 /2) where K 00 , K 01 and K 10 are constants, V co is an initial value of the control voltage, T is an ambient temperature and ΔF is a frequency offset amount, a D/A converter for converting the digital control voltage into an analog control voltage, and a voltage-capacitance converter for receiving the analog control voltage and generating a control signal to be supplied to the crystal oscillator according to the received analog control voltage, wherein the frequency of the crystal oscillator is controlled according to the control signal.

Antibody coated crystal chemical sensor

Abstract: A sensor for detecting the presence of a particular chemical by determining the absolute frequency shift in the oscillating frequency of an antibody-coated oscillator. Specific antibodies deposited on a high Q crystal oscillator detect the change in frequency as chemical particulates become trapped by the antibodies and change the effective mass of the crystal. In one embodiment, two oscillating crystals are used, one that has been coated with the antibodies, and one that is uncoated. This permits detection of frequency differences between the oscillating frequencies of the two crystals, thus eliminating pressure, temperature, and humidity corrections that conventionally must be made. The sensor maintains a high specificity by using antibodies that are specifically related to the chemical to be detected, while achieving relatively good sensitivity by using high Q oscillators, such as quart or sapphire, and eliminating drift problems due to temperature, pressure, and humidity. In a second embodiment, a single crystal is used having antibodies coated at specific nodal locations associated with harmonics of the fundamental frequency of oscillation of the crystal. Harmonic amplitudes are measured to determine the presence of the chemical of interest.

Crystal oscillator with quartz vibrator having temperature detecting faculty, quartz vibrator for use therein, and method of measuring temperature using quartz vibrator

Abstract: A crystal oscillator for generating an output oscillation whose frequency is maintained constant independently of the variation of temperature including a first quartz vibrator arranged in a heating unit which includes a thermostat and vibrating at a fundamental frequency, a second quartz vibrator arranged also in the same heating unit and vibrating at a third overtone frequency, a frequency multiplying circuit for multiplying the fundamental frequency by three, a frequency comparator for comparing the fundamental frequency multiplied by three with the third overtone frequency to derive a frequency difference which represents a temperature of the thermostat, and a temperature controlling circuit for controlling the temperature setting of the thermostat in accordance with the detected frequency difference. Any one or both of the fundamental and third overtone oscillations may be derived as an output oscillation. The first and second quartz vibrators are constructed by a single common quartz substrate, a first pair of electrodes each applied on respective main surfaces of the quartz substrate, and a second pair of electrodes each applied on respective main surfaces of the quartz substrate.

BVA-type quartz oscillator for spacecraft

Abstract: The performance of an oscillator using a BVA-type stress-compensated cut resonator is discussed. This oscillator design has demonstrated 24-h aging rates of >

Piezo electric resonator temperature sensor

Abstract: The temperature of a quartz crystal oscillator is determined by comparison of a pair of inharmonically related overtone oxcillations of the same vibrational type, e.g. a thickness shear mode, and of the same overtone order. The use of inharmonically related signals relaxes the contraints on crystal design. The technique may be employed in a crystal controlled frequency synthesizer to provide a feedback signal for maintaining constant output frequency.

Crystal oscillator having frequency adjustment responsive to power supply voltage

Abstract: Frequency compensation for a crystal oscillator circuit whose oscillation frequency is dependent on source voltage applied thereto. When a capacitor is added to the frequency compensation terminal of the crystal oscillator circuit, the circuit changes the oscillation frequency thereof on the basis of the capacitance of the capacitor. A source voltage detector compares the source voltage being applied to the crystal oscillator circuit with a predetermined reference voltage and produces a control signal matching whether the source voltage is higher or lower than the reference voltage. On receiving the control signal, a control switch turns on or off the contact thereof to add or not to add the capacitor to the frequency compensation terminal. Assuming that the characteristic of the crystal oscillator circuit is such that the oscillating frequency decreases with the decrease in the source voltage, when the source voltage is low, the capacitor for frequency compensation is not added so as to increase the oscillation frequency of the crystal oscillator. Conversely, when the characteristic is such that the oscillation frequency increases with the decrease in the source voltage, the capacitor is added so as to decrease the oscillation frequency.

Voltage controlled temperature compensated crystal oscillator using 2-port crystal resonator

Abstract: Generally, the frequency-vs.-temperature characteristic of voltage-controlled temperature compensated crystal oscillators (VCTCXO) varies when their oscillation frequency is shifted. In an effort to solve the problem, the authors developed a VCTCXO using a 2-port crystal resonator with a special electrode structure. The VCTCXO with the 2-port crystal resonator can have two load capacitances, i.e., a load capacitance for temperature compensation and a load capacitance for shifting the oscillation frequency. Therefore, the VCTCXO can compensate for temperature changes and shift the oscillation frequency independently. An electric equivalent circuit for the 2-port crystal resonator is introduced, and fundamental equations are derived from the equivalent circuit for determining the extent to which the oscillation frequency varies with the load capacitances, with comparison made between measured and calculated values. >

Temperature compensated crystal oscillator employing new shape GT cut quartz crystal resonator

Abstract: The authors describe a temperature internally compensated crystal oscillator using the novel GT-cut quartz crystal resonator formed by an etching method. The object is to clarify if drain output resistance R/sub d/ and resistance R/sub qs/ connected in series to the resonator in elements constructing a CMOS oscillator circuit which suppress spurious vibrations, influence oscillation frequency and frequency-temperature behavior. First, a CMOS quartz crystal oscillator circuit is transformed into an equivalent circuit, and an equation which gives oscillation frequencies is derived from Kirchhoff's law. Second, since the equation is given as a function of R/sub d/ and R/sub qs/, it is theoretically predicted and experimentally shown that R/sub d/ and R/sub qs/ influence the oscillation frequency and the frequency-temperature behavior. >

A space oscillator with cylindrical oven and symmetry

Abstract: A cylindrical oven whose axis is the axis of the 10 MHz quartz resonator (in HC 40 can) is studied. Thermal flux is canalized on its axis at a place where the thermistor is located. Thermal exchanges include conduction and radiation effects, reduced, however, by the use of a dual envelope. The oven is studied through a scheme which uses electric analogs, and results are obtained for external temperatures between -25 degrees C and +60 degrees C. The thermistor is located on the resonator can where temperature is very close to the turnover point. The analytical modeling uses oven symmetry. Thermal regulation design includes a frequency analysis between 0.001 Hz and 10 Hz, with a 60-dB gain. A response analysis to temperature steps and to linear temperature variation (0.5 degrees C/mn) is also performed. The thermal gain and dynamical behavior of oven electronics is deduced. Insertion of a correction network with phase advance in oven electronics yields a fast oven response. The oscillator improvements in space conditions are described. >

Quartz crystal oscillator used as temperature sensor

Abstract: A method for obtaining temperature data from a quartz crystal is described. To implement it, the first and third overtones of AT- and SC-cut crystal behavior with temperature have been studied. The AT-cut crystal shows instabilities at unpredictable temperature point while the SC-cut crystal has no activity dips in its c mode of vibration. A circuit to obtain a frequency very sensitive to and linear with temperature changes from the crystal fundamental and third overtone has been developed. Crystal design ideas obtaining the optimum frequency vs. temperature compensation are also explained. The goal of this technique is to compensate frequency vs. temperature variations of a quartz crystal oscillator, obtaining a factor-of-ten improvement over others that use thermistors as temperature sensors. >

Frequency standards for communications

Abstract: : The fundamentals of quartz and atomic frequency standards are reviewed. The subjects discussed include: crystal resonators and oscillators, atomic oscillators, oscillator types, and the characteristics and limitations of temperature-compensated crystal oscillators (TCXO), oven-controlled crystals oscillators (OCXO), rubidium frequency standards, cesium beam frequency standards and hydrogen masers. The oscillator instabilities discussed include: aging, noise, frequency vs. temperature, warmup acceleration effects, magnetic field effects, atmospheric pressure effects, radiation effects, and interactions among the various effects. Guidelines are provided for oscillator comparison and selection. A discussion of time transfer techniques, and specifications are also included, as are references and suggestions for further reading.

Crystal oscillator for use in timepiece of battery-powered portable apparatus.

Abstract: circuit whose oscillation frequency is dependent on source voltage applied thereto. When a capacitor is added to the frequency compensation terminal of the crystal oscillator circuit, the circuit changes the oscillation frequency thereof on the basis of the capacitance of the capacitor. A source voltage detector compares the source voltage being applied to the crystal oscillator circuit with a predetermined reference voltage and produces a control signal matching whether the source voltage is higher or lower than the reference voltage. On receiving the control signal, a control switch turns on or off the contact thereof to add or not to add the capacitor to the frequency compensation terminal. Assuming that the characteristic of the crystal oscillator circuit is such that the oscillation frequency decreases with the decrease in the source voltage, when the source voltage is low, the capacitor for frequency compensation is not added so as to increase the oscillation frequency of the crystal oscillator. Conversely, when the characteristic is such that the oscillation frequency increases with the decrease in the source voltage, the capacitor is added so as to decrease the oscillation frequency.

Integrated MOS quartz oscillator with single crystal connector - gives frequency stability using series-resonance and two=stage amplification

Abstract: The integrated quarz oscillator comprises two amplification stages (1, 2), a single connection pin (P) for an external crystal and a feedback capacitor (CG). The series-resonant crystal (Q) acts as source impedance for amplifier stage 1, which contains a single MOS transistor (T1), while stage 2 contains 2 MOS transistors acting as an inverter. The prod. of the 2 stage gains, V1 and V2 respectively, is greater than 1 at the oscillator resonance frequency and elsewhere less than ADVANTAGE - Redn. of circuit complexity and number of pins promotes reliability and compactness. Series resonance mode gives stable oscillator frequency and immunity to mfg. tolerances.