Showing papers on "Crystal oven published in 1977"

Narrow deviation voltage controlled crystal oscillator for mobile radio

Abstract: A linear sensitivity voltage controlled crystal oscillator of the type including a resonator coupled to a negative resistance generator. The resonator comprises a crystal connected in series with a voltage variable capacitance device. The response of the resonator is linearized by the addition of an inductance across the voltage variable capacitance device. A resistor is shunted across the crystal to prevent oscillation at spurious resonances of the resonator.

Crystal oscillator compensated against frequency shift due to acceleration

Abstract: An electrical oscillator having a piezoelectric resonator, the shift in frequency of which is automatically compensed when the oscillator is subjected to an acceleration. Consequently, the oscillator is practically insensitive to high accelerations and can be used as a frequency standard in an aircraft or space vehicle. Said oscillator comprises, in an oscillator loop, the resonator and a capacitance for adjusting frequency connected in series with the resonator. The adjusting capacitance is formed of at least one variable capacitor. Means sensitive to acceleration are provided for controlling the variable capacitor so that the frequency shift caused by the variable capacitor is opposed to the frequency shift of the resonator caused by acceleration.

Electronic timepiece utilizing main oscillator circuit and secondary oscillator circuit

Abstract: An electronic timepiece having a main oscillator circuit including a first quartz crystal vibrator as a time standard and also having a secondary oscillator circuit including a further quartz crystal vibrator as a time standard for reducing the affect of temperature on the accuracy of the timepiece by utilizing the different temperature characteristics of the respective time standards is provided. The main oscillator circuit produces a high frequency time standard signal having a first frequency rate that is determined, at least in part, by the temperature characteristic of the first time standard, which characteristic includes an inflection peak at a specific temperature. The second oscillator circuit produces a second high frequency time standard signal having a second predetermined frequency, determined, at least in part, by the temperature characteristic of the second time standard being distinct from that of the first time standard. Phase detection circuitry is provided for producing a phase detection signal in response to detecting a predetermined frequency difference in phase between the first and second high frequency time standard signals when the temperature is 10° higher or lower than the specific temperature at which the first time standard has its inflection peak. A display is provided for displaying actual time in response to receiving a low frequency time signal produced by divider circuitry. A frequency adjustment circuit is coupled intermediate the phase detection circuitry and the divider circuitry for adjusting the frequency of the low frequency time signal produced by the divider circuitry when a phase detection signal is applied thereto.

Method and apparatus for near-synchronization of a pair of oscillators, and measuring thereby

Abstract: The measuring system of the disclosure has two oscillators of different frequencies. The oscillations of the high frequency oscillator are counted for a time corresponding to a portion, for example one-eighth, of the period of the low frequency oscillator. If the count is less or greater than a selected count, for example 4,096, the frequency of the low frequency oscillator is corrected by approximately one high frequency period in the one-eighth low frequency period. By this method the oscillators are brought into near-synchronism, so that there are counted exactly 4,096 high frequency oscillations during the one-eighth period of the low frequency oscillator, but neither 4,097 or more, nor 4,095 or less. The correction is accomplished by excluding or including one at a time, various resistors in the frequency determining portion of the low-frequency circuit by the use of transmission gates in parallel with the resistors. The system may be used to measure, for example, weight. The capacity in the frequency determining portion of the high frequency oscillator is increased as a function of the weight. The frequency of the high frequency oscillator is thereby reduced. Suitable circuits respond to count the changed oscillations relative to the unchanged calibration period of the low frequency oscillator to derive a measure of the weight.

Passive intrusion detection system

Abstract: An intrusion detection system in which crystal oscillators are used to provide a frequency which varies as a function of fluctuations of a particular environmental property of the atmosphere, eg, humidity, in the protected volume The system is based on the discovery that the frequency of an oscillator whose crystal is humidity sensitive, varies at a frequency or rate which is within a known frequency band, due to the entry of an intruder into the protected volume The variable frequency is converted into a voltage which is then filtered by a filtering arrangement which permits only voltage variations at frequencies within the known frequency band to activate an alarm while inhibiting the alarm activation when the voltage frequency is below or above the known frequency band

Thickness shear resonator for use as an over-tone quartz crystal

Abstract: A thickness shear resonator used as an overtone quartz crystal for a quartz stabilized oscillator which has an operating frequency in the MHz range that has an excitation electrode on each of its plane parallel surfaces running in the x, z' plane and where the thickness of the vibrator in the y' direction is determined by the distance of these surfaces from one another wherein the vibrator presents a dimensional ratio between its dimensions measured in the z' direction and its thickness which is determined by a fundamental quartz crystal frequency having a value of 1/3 of the operating frequency, thus, resulting in an oscillator which is not sensitive to influences from associated oscillating components.

Frequency stabilized microwave signal source

Abstract: The frequency of a microwave oscillator is stabilized by coupling a portion of the RF signal therefrom to an HF oscillator operating at a sub-multiple of the microwave frequency and producing a strong harmonic at the microwave frequency in order to cause the operation of the microwave and HF oscillators to be locked together. The HF signal frequency, which includes any drift in the microwave oscillator frequency, is divided down a specified amount and compared with the frequency of a stable crystal reference oscillator in a comparator. The output of the comparator is a DC error voltage which is proportional to any drift in the frequency of the microwave oscillator. This error voltage is applied to the microwave oscillator to cause the operating frequency thereof to be more nearly constant.

New method of detection of weak anharmonic modes of a quartz crystal and its applications for generating multicrystal resonance frequencies

Abstract: An experimental method has been described for detection of various oscillating modes of a quartz crystal and accurate measurement of their resonance frequencies. In effect, a parallel tunable L‐C circuit is coupled to the quartz crystal in a crystal oscillator circuit. As the L‐C resonant frequency approaches one of the crystal mode resonance frequencies, the crystal takes control and makes the crystal oscillator circuit generate this frequency. The method, thus, not only enables accurate determination of crystal mode resonance frequencies but also permits generation of a number of stable frequencies using a single quartz crystal.

Quartz Colpitts oscillator with varactor diode - is able to pull frequency over wide range and oscillates at higher harmonic

Abstract: The quartz Colpitts oscillator can be pulled over a width frequency range and oscillates at a higher harmonic. An inductor (L1) is coupled in series with the quartz crystal (Q). The inductor forms a series resonant circuit with the varactor diode used for frequency pulling and with a capacitive voltage divider (C1,C2). The resonant circuit is tuned to the diode average capacitance. A damping resistor is coupled in parallel with the crystal and is larger than the series resonant resistance of the crystal at the working harmonic but still low enough to prevent the crystal from being excited at its fundamental.

Quartz Crystal Parameters Measurement System

Abstract: A device for measurement of quartz crystal resonator parameters is presented. This device is using a synthesizer, the frequency of which is swept step by step to find the resonance of the crystal. With a phase loop, which controls the synthesizer's interpolator, the resonance frequency and the bandwidth of the crystal can be measured. A low-cost computer gives the values of the resistance and the Q factor. The time constants of the crystal and of the phase loop are studied to determine the best measurement speed of this automatic device.