Showing papers on "Frequency drift published in 1976"

Theory of oscillator instability based upon structure functions

Abstract: Structure functions are apparently unfamiliar to most engineers and the unifying role they play in oscillator instability theory has largely gone unrecognized. This paper introduces and places into perspective the role which Kolmogorov structure functions have in theory. It is demonstrated that the rms fractional frequency deviation (phase accumulation) introduced by Cutler and Searle is related to the first phase structure function; the two-sample Allan variance is related to the second phase structure function. In addition, it is shown how the two-sample Allan variance is related to the rms fractional frequency deviation under suitable conditions. The L-sample Allan variance is also identified in terms of the first phase structure function; it is shown to be an asymptotically unbiased estimator of the rms fractional frequency deviation squared if the latter existL The utility of higher order structure functions of frequency and phase in the theory of instability is also demonstrated; in particular, how the frequency drift and "flicker"-type noise convergence problems can be overcome.

CW ultrasonic bolt tensioning monitor

Abstract: This invention is a CW ultrasonic device for measuring frequency shifts of the peak of a mechanical resonance in a body. One application of the device is measuring the strain in a bolt. It also has other applications such, for example, as measuring the thickness of a body, measuring the depth of a flaw in a body, measuring the elongation of body and measuring changes in velocity of sound in a body. The body is connected, by means of a CW transducer, to electrical circuit means including a narrow band RF amplifier to form a closed loop feedback marginal oscillator that frequency locks the device to the peak of a mechanical resonance in the body. Thereafter, when the frequency of this peak changes, because of a physical change in the body, the frequency of the oscillator changes. The device includes an automatic frequency resonant peak tracker that produces a voltage that is related to a change in frequency of the oscillator. This voltage is applied to the RF amplifier to change the center of its frequency band to include the frequency of the peak and is a measure of the frequency shift. The device also includes a special transducer which requires contact to only one side of the body and provides high electrical isolation between its parts.

Wide range frequency modulation of narrow loop bandwidth phase-locked oscillators

Abstract: Frequency-modulated phase-locked loop oscillator with a special modulator bypassing the phase-locked loop to inject modulation voltage directly into the voltage-controlled oscillator of the loop to broaden the bandwidth of modulation.

Frequency synchronizing system for satellite communication

Abstract: A frequency synchronizing system for satellite communication, in which a reference frequency coming from a communications satellite is received by a receiving circuit. A first frequency variable oscillator is provided for generating a transmission signal. A second receiving circuit is provided for receiving through the communications satellite the transmission signal which is the output from the first frequency variable oscillator, A first frequency control circuit is provided for controlling the first frequency variable oscillator for making the frequencies of the outputs from the first and second receiving circuits equal to each other. A second frequency variable oscillator is provided for generating a signal of a frequency twice as high as the reference frequency. A frequency converter is provided for mixing the output from the first or second receiving circuit with the output from the second frequency variable oscillator to produce a signal of a difference frequency substantially equal to that of the transmission signal. A phase detector detects the phase difference between the transmission signal and the output from the frequency converter. A frequency control circuit is provided for controlling the second frequency variable oscillator with the output of the phase detector so that the output frequency of the second frequency variable oscillator is twice as high as the frequency of the reference signal on the communications satellite. The first frequency variable oscillator is replaced by a reference oscillator of constant frequency in a reference station.

Phase-locked loop frequency shift key modulator

Abstract: MSK modulating apparatus employing a phase-locked loop. The loop includes a programmable divider which divides the output frequency of the voltage controlled oscillator by a relatively high value if binary 1 information is to be transmitted and by a relatively low value if binary 0 information is to be transmitted. The output of the voltage controlled oscillator is also divided by an output divider to obtain the desired carrier frequency and then filtered to provide a sinusoidal output signal. The resulting output signal varies by a differential frequency above or below a carrier center frequency when transmitting binary 1 or binary 0 data, respectively.

Harmonic mixing and frequency measurement at 2.5 THz using Josephson junctions

Abstract: The frequency of quartz-crystal oscillators, operating near 120 MHz, has been multiplied by a factor of 21060 and mixed with the frequency of a discharge-pumped water vapour laser operating at 2.53 THz (118 mu m wavelength). The final stage of multiplication and harmonic mixing was performed using point-contact Josephson junctions, with harmonic numbers up to 156. The signal-to-noise ratio of the final intermediate frequency signal was limited by phase noise in the quartz-crystal oscillator, but was about 17 dB higher than that obtained when a klystron, phase-locked to the crystal oscillator, was used as a transfer oscillator. The power levels of the intermediate frequency signals from the Josephson mixer are discussed. The frequency of the laser when set to its Lamp dip was found to be 2527952.91+or-0.05 MHz.

Frequency synthesizer for transmitter/receiver using a phase locked loop

Abstract: A frequency synthesizer for use in a transmitter/receiver, comprising a voltage controlled oscillator, a programmable frequency divider for dividing the frequency of the output from the voltage controlled oscillator, a reference oscillator, a reference counter for dividing the frequency of the output from the reference oscillator, a phase detector for phase detecting the frequencies of the reference counter and the frequency divider for providing a control voltage to said voltage controlled oscillator, a transmitting/receiving mode selection circuit for selectively controlling the programmable frequency divider such that the frequency division rate thereof is different in the transmitting and receiving modes, a channel designating circuit, a first output terminal for withdrawing an output by mixing the output from the voltage controlled oscillator with the output from the reference oscillator, and a second output terminal for directly withdrawing the output from the voltage controlled oscillator, said transmitting/receiving mode selection circuit comprising a transmitter/receiver selection switch, and full adder means or a read only memory for storing in advance information concerning the frequency division rate of the frequency divider based on the output from the transmitter/receiver selection switch and the output from the channel designating circuit.

Television frequency synthesizer for nonstandard frequency carriers

Abstract: In a phase locked loop (PLL) tuning system for a television receiver, the capability of tuning channels with RF signals with non-standard frequencies arbitrarily near the respective standard frequencies is provided by making a frequency divider used in the PLL for establishing the frequency relationship of the local oscillator signal to the crystal oscillator signal controllable in a limited range corresponding to a frequency range less than the frequency separation between channels. As one feature of this system the divider is controlled in accordance with predetermined AFT signal conditions. As another feature, the division factor of the divider is initially offset from its nominal value corresponding to the standard frequency for the selected channel and thereafter the frequency of the local oscillator signal is controlled in response to the AFT signal.

Automatic frequency control for digital tuning systems

Abstract: Apparatus is provided for automatically compensating for frequency drift in a digitally tuned varactor tuner. An Automatic Frequency Control signal for tuning the varactor tuner is produced in response to the direction of a tuning error. A signal level detector is used to inhibit the AFC signal when weak signals are being tuned by the varactor tuner thereby preventing continuous searching by the tuning system.

Frequency counter for a television tuning system

Abstract: A tuning system for a television receiver includes a local oscillator which is controlled first by a phase lock loop arrangement and then by an AFT discriminator arrangement for tuning the receiver to non-standard as well as standard frequency carriers. The phase lock loop arrangement includes a programmable divider for dividing the local oscillator frequency by a programmable factor corresponding to the presently selected channel. When the local oscillator is being controlled by the AFT discriminator arrangement, the count accumulated by the programmable divider during a reference interval determines how far the local oscillator frequency has drifted from its nominal value. If a predetermined frequency offset has been exceeded, control is returned to phase lock loop control and the programmable factor is incrementally changed.

Digital frequency deviation detector useful in a television tuning system

Abstract: In a phase locked loop type of tuning system for a television receiver having provisions for tuning the receiver to non-standard frequency carriers having frequencies arbitrarily near respective frequencies of the standard broadcast carriers, a digital frequency deviation detector is provided to determine whether the frequency of at least one variable frequency signal developed by the tuning system is within a predetermined range of its nominal value. The frequency deviation detector includes a D type flip-flop to generate a signal whose frequency is equal to the difference between the frequency of the variable frequency signal and a fixed frequency signal. A counter is enabled during a predetermined portion of at least one cycle of the difference signal to count period (cycles) of the fixed frequency signal. The accumulation of at least a predetermined count indicates that the variable frequency signal is within a predetermined frequency difference with respect to the frequency of the fixed frequency signal. The frequency of the fixed frequency signal is substantially proportional to the nominal frequency of the variable frequency signal. Because the frequency deviation detector does not require components (e.g., capacitors) conventionally employed with analog type of frequency deviation detectors, it may be readily incorporated in a digital integrated circuit with, for example, other portions of a digital tuning system.

Frequency control for frequency agile pulse radar

Abstract: An automatic frequency control for causing a local oscillator to track the frequency of a transmitter such that the received echo of a transmitted pulse may be combined with the output of the local oscillator in a mixer to provide an intermediate frequency signal which is suitable for amplification, filtering and detection operations. The automatic frequency control includes an average frequency control loop for determining the average frequency of the local oscillator output signal, an electromechanical frequency transducer cooperating with a sample and hold circuit for providing a modulating signal to modulate the average frequency of the local oscillator output signal in response to the frequency of the next pulse to be provided by the transmitter, and a modulation gain control loop for controlling the gain of the modulating signal to compensate for variations in the transfer functions of the electromechanical frequency transducer and the sample and hold circuit.

Wireline tool for measuring bottom-hole pressure in pumping wells

Abstract: A data transmission system for use in transmitting data from a well to a surface location. The well data is converted to a voltage and used to control the frequency of an oscillator whose output frequency is transmitted to the surface. At the surface a second voltage-controlled oscillator is adjusted until its frequency and phase matches the signal transmitted from the well. The voltage required to match the frequency of the second oscillator to the frequency of the transmitted signal is then equal to the value of the well data.

Electronically controllable tuning device having a frequency synthesizer

Abstract: An electronically controllable tuning device includes a voltage controlled oscillator adapted to have an oscillation frequency controlled by a control voltage and simultaneously generate a fundamental wave of a predetermined frequency, a programmable frequency divider for dividing the fundamental wave frequency at a frequency division ratio corresponding to the control of a channel selection means and a phase locked loop adapted to compare the fundamental wave phase with the phase of the output of the programmable divider to generate a comparison output and feeding the comparison output back to the voltage controlled oscillator to control the output frequency of the voltage controlled oscillator. The tuning device further includes means for supplying as a local oscillation signal to an intermediate frequency generating mixer one of higher harmonic wave components of the fundamental wave.

Network for temperature compensation of an AT cut quartz crystal oscillator

Abstract: A network for temperature compensation of a crystal oscillator over an extended temperature range encompassing two points of inflection of the drift characteristic of an AT cut crystal. The oscillator is of the type having, in loop connection, an AT cut quartz crystal and a voltage variable capacitance device. The compensation network utilizes a three resistor, three thermistor electrical network for generating a temperature dependent bias voltage applied to the variable capacitance device to compensate for changes in the self-resonant frequency of the crystal due to temperature variation. A method for determining the component values for the compensation network is also disclosed.

Indirect FM modulation scheme using phase locked loop

Abstract: A phase space locked loop system used for performing indirect frequency modulation. A phase locked loop is comprised of a phase detector coupled to a low pass filter coupled to a voltage controlled oscillator with a feedback loop to the phase detector. Input signals provided by a crystal controlled oscillator are fed to the phase detector. A phase difference other than 90° between the voltage controlled oscillator output and the input signal will result in the phase detector generating an error voltage which is filtered by the low pass filter to alter the voltage controlled oscillator until its phase is 90° from the input signal. A modulating signal is injected into the phase locked loop which causes the voltage controlled oscillator to momentarily change frequency until the output of the phase detector changes enough to balance the modulating signal.

Receiver system for locating transmitters

Abstract: A receiver system for locating transmitters, such as underground transmitters carried by trapped miners, includes a power divider for splitting an incoming signal for supply to a plurality of frequency selective paths each having a mixer and a bandpass filter. The mixers are provided with different local oscillator signals to permit simultaneous tuning to a fundamental transmitter frequency and its harmonics. A local oscillator generator coherently produces the local oscillator signals by mixing a frequency N times greater than the center frequency of the bandpass filters with a frequency N times greater than a fundamental frequency to be received and dividing the mixing output by N.

Method for controlling frequency of electrical oscillations and frequency standard for electronic timepiece

Abstract: A frequency standard for an electronic timepiece comprising a low frequency oscillator and a high frequency oscillator of which the frequency is an integral multiple of a predetermined frequency of the lower frequency oscillator. A phase difference detector is coupled to the lower and higher frequency oscillators to produce a signal occurring at intervals depending on the phase difference between the two oscillators. A frequency divider is provided to divide down the frequency of the signal by the integral multiple to produce a phase difference signal. The phase difference signal is algebraically added to the lower frequency oscillator signal to generate an output signal of which frequency is equal to that of the high or frequency oscillation signal divided by the integral multiple.

Improvement of TRAPATT performance with optically generated carriers. [TRAPATT microwave sources]

Abstract: It is demonstrated that a number of the difficulties which have thus far limited the application of the TRAPATT oscillator may be overcome by optically generating carriers within the device active region. Illumination with a short light pulse at the beginning of the bias pulse extents the ranges of bias, circuit tuning, and temperature over which the duration of leading edge jitter is short. Illumination during the application of the bias pulse significantly shifts the oscillation frequency. It is shown that this effect may be used to eliminate undesirable intrapulse frequency drift with shaped light pulse. Also, frequency switching in time-frames approaching one rf period are accomplished, which opens up new applications for the TRAPATT oscillator.

On the possibility of nonlinear phase bunching effects in the extraordinary mode decametric radio emission of Jupiter.

Abstract: Electron phase bunching can become important on a millisecond time scale in coherent extraordinary mode waves of the amplitude estimated for the Jovian and terrestrial radio emissions, assuming that the emission frequency is slightly above the local cyclotron frequency. Through a coherent interaction a significant fraction of the energy of cyclotron resonant electrons can be transferred to such waves. If the in situ wave fields are sufficiently coherent, phase bunching effects may control the high-resolution dynamic spectrum of the emissions. Field gradients may prevent such phase bunching in the terrestrial magnetosphere, but not in the Jovian decametric source region. Phase-coherent theories suggest two possible explanations of the frequency drift of Jovian millisecond radio bursts. (AIP)

Improvement of TRAPATT performance with optically generated carriers

Abstract: It is demonstrated that a number of the difficulties which have thus far limited the application of the TRAPATT oscillator may be overcome by optically generating carriers within the device's active region. Illumination with a short light pulse at the beginning of the bias pulse extends the ranges of (i) bias, (ii) circuit tuning, and (iii) temperature over which the duration of leading edge jitter is short. Illumination during the application of the bias pulse significantly shifts the oscillation frequency. It is shown that this effect may be used to eliminate undesirable intra-pulse frequency drift with shaped light pulses. Also, frequency switching in time-frames approaching one RF period are accomplished, which opens up new applications for the TRAPATT oscillator.

Oscillator frequency control loop

Abstract: In an oscillator circuit controlled by a reference frequency a voltage regulated oscillator is controlled by the output voltage from digital-to-analog converter whose digital input is obtained from an up/down counter. The counter is controlled by the output from a frequency difference detector which compares the output of the voltage control oscillator and the reference frequency. A threshold circuit is connected between the frequency difference detector and the activation and up/down control inputs of the counter so that the counter is activated only when the frequency difference exceeds a predetermined amount.

Injection-locked voltage controlled oscillators

Abstract: An improved frequency memory system of the type using a voltage controlled oscillator is described. Incoming RF signals are power divided with a first power divided portion applied to a frequency discriminator where a voltage level signal indicative of frequency is derived. This voltage level signal is shaped and applied to the volage controlled oscillator wherein the oscillator is broadly tuned to the incoming frequency. A remaining portion of the power divided signal is applied directly to the RF circuit portion of the VCO oscillator to injection lock the VCO oscillator to the incoming signal.

Variable frequency oscillator

Abstract: of the Disclosure A variable frequency oscillator comprises an oscillating loop and a variable phase shifter for imparting one of two different phase shifts depending upon the polarities of a DC control voltage to a sig-nal from the oscillating loop. The phase-shifted signal has its amplitude controlled by the amplitude of the control voltage and is combined with the signal in the oscillating loop. The vector sum of the combined signals determined the phase angle of the oscillator signal and hence the frequency thereof.

Temperature compensated surface acoustic wave oscillator

Abstract: Disclosed apparatus compensates for the parabolic temperature induced frequency drift characteristic of a surface acoustic wave tuned oscillator. The apparatus includes a pair of varactor diodes and a temperature sensitive voltage supply. The diodes are series connected and coupled in circuit with the oscillator to affect the frequency thereof. The voltage supply connects to the common connection of the diodes, for producing control voltages thereat. Each varactor diode is chosen to have a δ > 1; and the control voltage varies linearly with temperature. This results in a varactor diode capacitance versus temperature characteristic which is a continuous, true parabolic function providing precise compensation for the thermal drift of oscillator frequency.

Wide-band frequency-controlled crystal oscillator

Abstract: An oscillator formed of an amplifier with a feedback loop containing two parallel connected crystals in series with a voltage variable capacitance. The two crystals have respective resonance frequencies above and below the limits of a wide band over which the oscillator frequency can be varied by a control voltage. Frequency versus control voltage linearity is improved by inductances inserted in parallel and in series, respectively, with the lower and higher frequency crystals.

Microwave transistor oscillator for wide band frequency tuning

Abstract: A transistor oscillator for microwave frequency ranges has a transistor with interelectrode capacitances used for feedback. A series connection of a voltage controlled variable capacitor and line element are connected to the collector of the transistor as a frequency determining element. A line element is connected to the base for feedback and bias means are connected to the base and emitter through high frequency choking means constructed of two quarter wavelength line elements, one of which is arranged in no-load fashion. An attenuation network for frequency selection action is connected to the collector feedback path to dampen the oscillating circuit and prevent frequency jumping of the oscillator outside of the band intended for useful operation.

Ammeter for grid system transmission lines - has oscillator with ferromagnetic crystal affected by conductor's magnetic field

Abstract: An ammeter for grid system transmission lines has meter readings are transmitted by a sender. The latter (11) has an oscillator (13) whose frequency determining element (12) is an iron-yttrium garnet single crystal magnetically coupled with the highest voltage conductor. Its frequency is a function of magnetic field. A receiver (14), outside the range of magnetic field, has a frequency discriminator converting received frequency changes into amplitude fluctuations proportional to the measured current intensity. This arrangement enables measurements to be made from installations inaccessible during working. The readings have good linearity. The oscillator (13) is so tight that it can be fitted directly to the grid system conductors.

Method and apparatus for frequency stabilizing oscillators

Abstract: Frequency stabilization of an oscillator by compensating for slow frequency variations due to ambient temperature variations is achieved by diverting a fraction of the oscillator output to a waveguide line section having a coefficient of thermal expansion/° C which is greater than the coefficient of relative frequency drift/° C of the oscillator comprising, in sequence, a variable attenuator and a movable short. The variable attenuator is used to primarily adjust the amplitude of the diverted signal by one-half the desired amount preferably without varying the phase of the diverted signal. The movable short is primarily used for signal phase adjustment while simultaneously reflecting the attenuated signal back through the attenuator and towards the oscillator output. Temperature variations which cause impedance changes in the oscillator, and in turn frequency changes at the output thereof, similarly affect the components of the divergent waveguide line section to produce reactive load variations therein of corresponding magnitude and opposite sign to the impedance changes in the oscillator.

High accuracy sweep oscillator system

Abstract: A voltage controlled sweep oscillator system which is stepped in frequency, avoiding transitional frequencies. Only discrete frequencies are provided by dividing the system into two segments wherein each segment comprises a voltage-controlled oscillator (VCO) in a phase-locked loop. A multiplexer provides one VCO signal to the output while the other VCO is stepping its frequency, and vice versa. Frequency control in each segment is achieved by comparing the divided output of a VCO with a reference frequency signal and making adjustments to cancel any errors that may appear.