Showing papers on "Crystal oven published in 1975"

Measurement of the Short-Term Stability of Quartz Crystal Resonators and the Implications for Crystal Oscillator Design and Applications

Abstract: A new technique is presented which makes it possible to measure the inherent short-term stability of quartz crystal resonators in a passive circuit. Comparisons with stability measurements made on crystal controlled oscillators indicate that noise in the electronics of the oscillators very seriously degrades the inherent stability of the quartz resonators for times less than 1 s. A simple model appears to describe the noise mechanism in crystal controlled oscillators and points the way to design changes which should improve their short-term stability by two orders of magnitude. Calculations are outlined which show that with this improved short-term stability it should be feasible to multiply a crystal controlled source to 1 THz and obtain a linewidth of less than 1 Hz. In many cases, this improved short-term stability should also permit a factor of 100 reduction in the length of time necessary to achieve a given level of accuracy in frequency measurements.

Optical frequency doubler using electro-optic crystal with improved feedback control of crystal phase match

Abstract: An optical frequency doubling arrangement is disclosed in which the indices of refraction of light in a frequency doubling electro-optic crystal are controlled by both electric field pulses applied across the crystal and heater control pulses for controlling the temperature of an oven in which the crystal is mounted. Both the electric field pulses and the heater control pulses have a duty cycle determined by the detected optical power output from the crystal at the desired double frequency, the heater control pulses being responsive to the measured oven temperature as well. The arrangement is especially suitable for doubling the frequency of 1.06 μm laser beams.

Crystal oscillator circuit

Abstract: A known crystal oscillator circuit is modified to improve the starting of oscillations therein when a low supply voltage is employed. The oscillator circuit includes two complementary field effect transistors connected in a known manner to each other and a frequency determining circuit including a crystal. The modification includes a first additional field effect transistor having its drain-source path connected in parallel with the drain-source path of one of the oscillator field effect transistors or a second additional field effect transistor having its drain-source path connected in parallel with the drain-source path of the other of the oscillators field effect transistors. The first and second additional field effect transistors are of the same conductivity type as the oscillator field effect transistor it is in parallel with.

Quartz crystal oscillator

Abstract: PURPOSE:To lower the active impedance of AT cut quartz crystal oscillator by decreasing the width of rectangular AT cut quartz crystal oscillator, and to secure a compact and high-efficiency quartz crystal oscillator for watch use.

Low Frequency Noise Quartz Crystal Oscillator

Abstract: For years, engineers and scientists have been plagued by an extremely undesirable property of the quartz crystal unit-its significant frequency shift as a function of drive level for drive levels in excess of 10 to 100 ?W. This fact was reported by Hammond [1]. As a result, all precision and moderate precision quartz oscillators have been operated at low drive in an effort to avoid the phenomena. The author has discovered, however, that this unique property of the quartz resonator can be effectively utilized in the design of the quartz oscillator with the result of substantial improvement in oscillator short-term frequency stability. Futhermore, since the crystal frequency-drive characteristic is repeatable, maintenance of moderately high crystal drive in the oscillator circuit will not result in long-term frequency instability in excess of that required for the majority of radar and communication systems [2].

NTS-1 (TIMATION-III) Quartz and Rubidium Oscillator Frequency Stability Results

Abstract: : The report describes frequency stability results obtained from the NTS-1 satellite. NTS-1 has three on-board frequency sources: one quartz oscillator and two rubidium resonators. These are used to derive the precise time and frequency signals radiated by the spacecraft. The data taken from each of three 2.5-hr daily passes are time difference (range) or frequency difference (doppler). These data are incorporated into a single value for each pass which is subsequently used in computing long-time Allan-variance results. The results presented here employ single-frequency measurements at 335 MHz. Analysis of these results indicate an effect on measured frequency stability that correlates with a resonant term in the orbit. The results further indicate the rubidium frequency depends on the spacecraft temperature, which confirms previous NRL preflight analysis.

Frequency range selectable oscillator for multichannel communication system

Abstract: To provide the required multiple channels for an aircraft communications system, a crystal controlled reference oscillator includes a tunable circuit for changing the base reference frequency provided by a crystal. The base reference frequency of the crystal controlled reference oscillator is pulled in frequency by changing the capacitance shunting the crystal. Two transistor switches change appropriate capacitors in series with the usual oscillator capacitor to obtain the capacitance values needed to pull the base reference frequency and thereby provide additional reference frequencies. The transistor switches are controlled by pilot actuated controls that operate a sliding display mark over a digital frequency indicator.

Low noise parametric varactor diode crystal oscillator

Abstract: A low noise frequency source utilizes a varactor diode to form a parametric crystal oscillator which may be frequency multiplied to the desired microwave frequency, for radar applications.

Wide-range temperature compensation by addition of two crystal-resonator frequencies: practical results with quartz and LiTaO3

Abstract: Practical results are presented on a novel method for compensating the frequency drift of crystal oscillators. The digital summing of a 300 kHz quartz and a 200 kHz LiTaO3 crystal resonator results in a sum frequency whose temperature drift is 10 times smaller than the drift of quartz or LiTaO3.

Time-keeping apparatus

Abstract: A time-keeping apparatus uses a crystal oscillator and electronic frequency dividers, as well as an electronically regulated mechanical time-keeping system (balance wheel system) which is part of an indicating system. The indicating system is driven at at least two different rpm's; at least one of these rpm's is effectively controlled to be higher and at least one of these rpm's can be controlled to be lower than a nominal rpm corresponding to the frequency of oscillation of the crystal oscillator, which may be of quartz. A storage circuit, in the form of a bistable multivibrator, has one input coupled to an output of a frequency divider which, in turn, is controlled by the output from the crystal oscillator. The other input to the storage circuit is provided with input pulses derived from the indicating system or from the electronically controlled mechanical time-keeping system, which have very nearly the same frequency as the pulses of the output of the frequency divider fed from the crystal oscillator. The output from the bistable multivibrator is coupled, via a switching circuit, to the electronically controlled balance wheel system.

Controlled high frequency transistor crystal oscillator

Abstract: A series-resonant crystal provides ac emitter coupling for a current switch whose output is fed back to its input to sustain oscillations at the resonant frequency of the crystal. A mixer circuit is provided so that the feedback is positive for small signal amplitudes whereby oscillations build up spontaneously when the circuit is switched on and then controls the feedback automatically so that it becomes negative for large signal amplitudes. This limits the output without resort to device saturation or cut-off, both of which adversely affect the speed, and as such, limit the high frequency performance of the oscillator.

Quartz crystal compensation circuit

Abstract: A compensation circuit is provided for a piezo-electric quartz crystal in a filter circuit for reducing the influence of the secondary resonance frequencies of the crystal on the filter characteristic. The Q-value of the crystal at one or several secondary resonance frequencies is reduced by connecting to the crystal a two-terminal network the impedance of which has a real and an imaginary part so that the real part gives an ohmic contribution which at the resonance frequency of the imaginary part reduces the Q-value of the crystal.

Devices using piezoelectric Ti3 BX4 compounds

Abstract: A crystal resonator is disclosed of a single crystal of the approximate composition Tl 3 BX 4 having two parallel surfaces normal to a zero temperature coefficient of frequency direction and having an electrode mounted on each surface, where B is vanadium, niobium, or tantalum, and X is sulfur or selenium. A filter is disclosed of a crystal resonator coupled to a capacitor or more than one crystal resonator in series each coupled to a capacitor. A voltage controlled crystal oscillator resonator is disclosed of a crystal resonator in parallel with an inductor and a varactor.

Crystal ranging apparatus for determining range within which resonant frequency of crystal lies

Abstract: Apparatus for ascertaining that the resonant frequency of a crystal frequency determining element lies within a predetermined frequency range is disclosed. A crystal whose frequency is to be measured is connected to an oscillator which provides vertical and horizontal deflection signals to a cathode ray tube device. Two crystal controlled signal generators provide series of short duration output impulses which are applied to the control grid of the cathode ray tube. One oscillator operates at the upper frequency limit of the frequency range, and the other oscillator operates at the lower frequency limit. If the crystal undergoing tests lies between the two frequencies of the two reference generators, two spots appearing on the screen of the cathode ray tube will rotate countercurrent with one another. If the frequency of the crystal undergoing test lies outside of the frequency range fixed by the two signal generators, those spots will rotate in the same direction, either clockwise or counterclockwise, depending upon whether the frequency of the crystal lies above or below the desired range.

Test set for measuring impedance and power dissipation of a crystal

Abstract: A crystal test set comprising an oscillator circuit in which a crystal under test is an integral part. The resistor substitution technique is employed in which the crystal and a variable resistor are alternately connected into the oscillator circuit. With the resistor in the circuit, the circuit is tuned to the resonance frequency of the crystal. The value of the resistor is adjusted to produce a voltage across the resistor equal to the voltage across the crystal. The adjusted value of the resistor is measured and corresponds to the crystal impedance. A measuring circuit, responsive to the voltage drop across the crystal, provides a direct measure of the crystal power dissipation.