Showing papers on "Voltage-controlled oscillator published in 1971"

Physiological pressure sensing and telemetry means employing a diode connected transistor transducer

Abstract: Pressure measurement apparatus and method, the apparatus having a pressure sensitive element, an audio oscillator, a transmitter, a receiver, a frequency-to-voltage converter and a read-out device The pressure sensor is connected to and capable of varying the frequency of the audio oscillator as a function of the pressure applied to the sensor The audio oscillator is connected to and capable of modulating the signal of the transmitter The pressure sensor, audio oscillator and transmitter are implanted internal to the scalp of a living test subject, the pressure sensor being placed between the skull and the dura mater Additionally, a remote receiver is connected to a frequency-to-voltage converter and is capable of receiving the radio frequency signal transmitter by the transmitter and supplying the detected audio oscillation of the radio frequency signal to the frequency-to-voltage converter The frequency-to-voltage converter is capable of supplying a variable voltage to the read-out device, depending upon the frequency of the input signal delivered by the receiver The read-out device is capable of optically displaying and/or recording the amount of signal voltage being fed to it by the frequency-to-voltage converter

Selection and processing system for signals, including frequency discriminator

Abstract: A signal selection and processing system for use with a broadband LORAN receiver in which the average of the strongest interfering signal having a predetermined duty cycle sets the AGC level and, via a special frequency discriminator, controls the frequency of a voltage controlled oscillator (VCO). The VCO output is used to shift the entire band of input frequencies so that said strongest signals fall into the attenuating notch of a notch filter while passing the other signals to the LORAN receiver.

Voltage-controlled crystal oscillators

Abstract: The quartz crystal oscillator is normally thought of as a stable generator of a fixed frequency. It is possible, however, to design and construct voltage tunable quartz crystal oscillators that can be electrically tuned over a frequency range on the order of ±0.3 percent of the crystal frequency. This is accomplished with a nonlinearity between frequency and voltage on the order of 0.1 percent. Moderately good long-term frequency stability and low phase noise is exhibited by the oscillators. A reactive network including varactor diodes is used to provide a voltage variable reactance which, in combination with a quartz crystal network, forms a resonator having an antiresonant frequency that is a linear function of tuning voltage. The basic reactance network is not practically realizable. However, the application of one of Norton's network transformation theorems results in a realizable network. The oscillator described is very simple in design and provides an inexpensive solution to a large number of signal processing and measurement problems.

Oscillator with switchable filter control voltage input for rapidly switching to discrete frequency outputs

Abstract: A voltage controlled oscillator controllable to discrete frequency outputs, which outputs are applied to a phase detector through divider circuits and compared to a reference signal of the same frequency, is controlled to discrete frequency outputs by variable voltages or variable width pulses, proportional to the difference in phase between the two signals, from the phase detector which pulses are applied to the oscillator through loop filters. Each loop filter is an RC circuit which integrates the pulses and serves as a memory to retain a relatively constant voltage thereacross. Therefore, when a specific loop filter is switched into the circuit the voltage controlled oscillator is rapidly switched to a discrete frequency output proportional to the voltage stored in the loop filter.

Variable speed plural motor control system with incremental speed synchronization

Abstract: A system for controlling the speed and synchronization of two ac motors comprises a master vco (voltage-controlled oscillator) for providing timing pulses to drive the master inverter which energizes the first a-c motor. A system speed control pot provides a speed set signal to the master vco, and also to a slave vco which controls the slave inverter that energizes the second a-c motor. A phase detector receives first and second lowfrequency input signals from the loads driven by the motors. A count-up register receives high-frequency pulse signals from the master vco and, through a dac (digital-to-analog converter), provides a positive-going ramp signal which has its reset portion determined by an output signal from the phase detector. A countdown register receives high-frequency pulse signals from the slave vco and, through another dac, provides a negative-going ramp signal which has its reset portion determined by a second reset signal from the phase detector. These opposite-slope ramp signals are summed with a signal from the phase detector to provide a d-c control signal which is used as a second input signal to the slave vco, thus maintaining motor synchronization. An out-of-sync signal overrides the d-c control signal and provides a modified d-c signal to the slave vco to drive the second motor toward synchronization. The d-c control signal can also be modified by a position control signal, to provide an incremental position variation of the second a-c motor without disturbing the synchronized speed relationship of the two motors.

Phase lock loop and frequency discriminator employed therein

Abstract: A phase lock loop employs a frequency discriminator having a relatively slow response to pull a voltage controlled oscillator into frequency lock with an input signal. After frequency lock the output of the frequency discriminator is nulled and a phase detector becomes effective to maintain phase lock. The frequency discriminator utilizes an operational amplifier to which both the input and oscillator signals are capacitively coupled through respective oppositely poled diode gates. A feedback capacitor, which is much larger than the input coupling capacitors, has charge transferred thereto fro m each coupling capacitors during alternate half cycles of the input and oscillator signals. The net charge across the feedback capacitor is a measure of the frequency difference between the input and oscillator signals, and is zero at frequency lock.

Wide frequency range voltage controlled oscillator with crystal controlled frequency stabilizing loop

Abstract: A controllable broad-band frequency generator comprising a voltage-controlled oscillator incorporated in a frequency controlled loop and an external controllable voltage source connected thereto, the control loop furthermore incorporating a digital crystal stable frequency discriminator and a combination device in which the direct voltage value derived from the voltage source is deducted from the output voltage provided by the frequency discriminator to obtain a direct control voltage for frequency controlling the voltage-controlled oscillator.

Coherent single sideband phase locking technique

Abstract: A phase-locked loop system capable of producing a synchronous reference of the proper frequency and phase to coincide with the frequency and phase of a transmitted single sideband modulated signal in order to properly demodulate the received signal for baseband recovery of the data. The invention makes use of post detection feedback to generate an error signal for locking a voltage control oscillator (VCO) to the correct phase for synchronous demodulation without using a transmitted carrier tone. The error signal which is equal to the sum of the baseband data waveform squared, plus the Hilbert transform of the baseband data waveform squared, times the sine of the phase difference between the VCO output and the input signal is generated from the delayed output of a first product demodulator, the delayed output of a second product demodulator and the output of the signal detector.

Channel selection device

Abstract: A reference signal frequency is generated for selection of a desired channel by a frequency sweep circuit comprising two sweep oscillators. The operations of the oscillators are reversed with each other at a predetermined frequency interval, and a voltage sweep main circuit and a voltage sweep sub-circuit are provided to apply a control voltage to a variable capacitance diode. The diode is contained in a tuner to control the sweep operation by the voltage sweep circuits in response to the reference frequency for channel selection.

Method and apparatus for the recovery of synchronous carrier in a digital communication system

Abstract: A carrier recovery and coherent detection system in a digital communication system having a quadrature or biphase PSK incoming signal, the incoming signal being divided and transmitted to a pair of radio frequency mixers, these mixers receiving their reference inputs from a voltage controlled oscillator in a phase lock loop, one of the reference signals being phase shifted relative to the other. The outputs of the two mixers are utilized to produce a phase error signal in the phase lock feedback loop to the VCO to synchronize the VCO with the carrier signal. The mixer outputs serve to indicate the proper digital symbol output.

Voltage controlled oscillator

Abstract: An oscillation circuit loop includes two phase shifters for advancing and delaying the phase of an input signal respectively, an adder for obtaining the vector sum of the output signals of these two phase shifters, and feedback means for the positive feedback of the output signal of the adder to an oscillation amplifier through a tank circuit. An external control voltage is applied to the adder so as to continuously vary the relative magnitude of the two signals added to each other by the adder. With an oscillator having such a construction, the degree of phase shift by the phase shifters and the value of Q of the tank circuit can be freely selected, and as a result, any desired sensitivity and phase control range can be freely obtained.

Phased locked loop with voltage controlled oscillator

Abstract: Phase locked loop having a voltage controlled oscillator, a phase comparator and filtering means all of which are integrated into a single monolithic block The comparator is of The balanced bipolar analog multiplier type and is supplied a control voltage by a multivibrator of the voltage controlled oscillator The collector load of the multivibrator is provided by the diode drops of the comparator's transistors The multivibrator is driven by a differential current divider which in turn is provided current by a constant common current source

Motor driving servo system comprising an integrator for the quantity relating to the error signal

Abstract: The servo system having a phase comparator for producing an error signal representative of the phase difference between an input reference periodic signal and an oscillatory signal for driving a motor. A voltage controlled oscillator controlled by the error signal to produce the oscillatory signal is provided with an integrator for integrating the error signal to produce an integration signal proportional to the result of the integration of the error signal and therefore to hold the instantaneous value of the integration signal when the error signal becomes zero. The integration signal is supplied to the oscillator in place of the error signal. the servo system is suitable for the drum and the capstan servos of rotary-head video tape recorders.

Voltage-controlled oscillator using complementary symmetry mosfet devices

Abstract: A voltage-controlled oscillator that is compatible with integrated circuit techniques and comprises complementary symmetry MOSFET devices to provide linear operation over several frequency decades, and exhibits high input impedance and minimum power consumption. The frequency of operation is controlled by a current source which is controlled solely by an input voltage. The constant current source linearly charges a capacitor through a bridge circuit. The bridge circuit which includes two complementary MOSFET transistors in each arm is connected across the current source and arranged so that when one transistor in an arm switches on the diagonally opposite transistor, in the other arm, also switches on. The rising voltage across the capacitor is used to change the state of a bistable multivibrator when a given threshold voltage is reached. The output of the bistable multivibrator discharges the capacitor, causes the capacitor to be charged in the opposite direction and provides an output terminal for the voltage-controlled oscillator.

Frequency comparator system

Abstract: Input frequency signal wave energy and the signal wave energy from a variable frequency oscillator are each squared and applied to separate monostable multivibrators. The output pulses from that multivibrator responsive to the input frequency signal wave energy are compared to the output pulses from that multivibrator coupled to the variable frequency oscillator. A resultant difference reflects the difference between the input frequency and the variable frequency oscillator frequency.

Minimum shift keying modulating apparatus

Abstract: A minimum shift keying transmitter utilizing a voltage controlled oscillator and logic circuitry for altering the frequency output of the oscillator in accordance with the logic level of the binary data to be supplied while preventing phase discontinuities in the output signal.

Clock recovery system

Abstract: A clock recovery circuit for a data communication system, wherein the eye pattern for the data is sampled (by sampling the outputs of the slicer circuits ) and logic circuitry utilized to select only those transitions, i.e., slicer axis crossings, which should be located midway between the desired time sample points and to advance or retard the local clock in accordance with the samples for these transistions. The ratio of advance to retard decisions is utilized to generate, through use of a D to A converter, a control signal for correcting the frequency of the voltage controlled oscillator which serves as the local clock, so that both frequency and phase error correction is provided.

Variable frequency oscillator with substantially linear afc over tuning range

Abstract: A tuned transistor oscillator for use with an RF receiver includes a transistor amplifier having a tuned network coupled between the collector and base of the transistor. Feedback is provided by a capacitor coupled between the tuned network and the emitter of the transistor. The tuned network includes a transmission line, a variable capacitive reactance means in parallel therewith, a first variable capacitance diode in series with said reactance means, and a second variable capacitance diode serially connected to said line. The capacitance of said reactance means is varied to allow the oscillator to sweep the desired frequency range, and the first and second capacitance diodes are varied by a DC AFC (automatic frequency control) voltage provided by the discriminator of the RF receiver to prevent oscillator drift. Said first and second diode capacitances are arranged so that the first capacitance has its greatest effect at the lower end of the oscillator frequency range while the second capacitor has its greatest effect at the upper end of said range, thereby providing an AFC signal which varies the oscillator frequency by a substantially constant amount independently of the oscillator frequency.

Threshold extension phase modulated feedback receiver

Abstract: In a frequency modulation receiver; (1) a feedback loop returns a control voltage to a voltage controlled oscillator from a bistable switching circuit used as a phase detector; (2) a fast signal acquisition unit of the main feedback loop provides a DC signal of proper sign and voltage to accelerate signal acquisition; (3) an assist means provides high frequency correction at the phase detector to avoid an overload effect occurring in the main feedback loop and a resulting threshold effect in the receiver; and (4) an IF summing circuit increases by a factor of four the amplitude signal-to-noise power ratio of the incoming signal prior to its introduction into the phase detector thereby making it possible for the phase detector to remain above threshold to a lower input signal-to-noise ratio.

Frequency measuring apparatus including phase locked loop

Abstract: The frequency of a received r-f input signal is accurately measured over a wide dynamic range synchronously detecting the signal with a superheterodyne receiver at intermediate frequency, phase locking the i-f signal to that of a reference signal, applying this reference signal to a frequency doubler whose output is applied to the modulating input of a balanced modulator energized on its carrier input by the output of another frequency doubler that doubles the frequency of the same local oscillator that is mixed with the input signal to provide the intermediate frequency signal. The output of the balanced modulator may then be applied to a tuned amplifier which provides as an output a signal of frequency exactly twice the frequency of the input signal that may then be conveniently measured, such as with a counter. The apparatus includes a phase-locked loop that adjusts the frequency of the local oscillator so that the input signal is beat down exactly to the intermediate frequency.

Rapid recycle oscillator with cutoff and thermal protection

Abstract: An oscillator provides an oscillation signal which is rectified and applied to a selectively dischargable capacitor. A control circuit monitors the charge on the capacitor and controls the cyclic operation of the oscillator to maintain the charge on the capacitor within predetermined limits, giving a visual signal indicative thereof. Temperature compensation means are included to terminate the operation of the oscillator while the temperature of the oscillator exceeds a predetermined value.

Data set system employing active filters and multivibrator timing

Abstract: A data set capable of converting binary encoded data signals into shift keying modulated signals for transmission over telephone lines. The timing element of the data set is a voltage controlled oscillator which is responsive to the binary encoded input information. The oscillator is adapted to operate at one frequency for the mark or binary one level of the input information and to operate at either one of two higher frequencies for the space or binary zero level of input information. An oscillator control means is responsive to the desired bandwidth and is operable to supply either one of two control voltages to the oscillator to generate either of said space frequencies. Operational amplifiers allow elimination of the conventional inductive components in both high and low pass filters thereby making each section an active filter section instead of being a passive filter. Each active filter section provides gain control which is not available in passive sections.

Switching system for keyboard

Abstract: A priority switching system for use with a keyboard of an electronic musical instrument comprising a plurality of input terminals having corresponding voltages applied thereto, a switching matrix including a plurality of linear switch arrays with each array responsive to operation of a corresponding key, and a multiplicity of voltage controlled oscillators coupled to the switching matrix. In the switching system the voltage controlled oscillators and the input terminals are selectively interconnected by the switching matrix on a priority basis so that the uppermost key, for example, is assigned to a first voltage controlled oscillator, and the next key, which need not be the next adjacent key, is assigned to a second voltage controlled oscillator, etc. In another embodiment, separate oscillators are coupled to each of the plurality of input terminals and a plurality of audio processing channels are coupled to the switching matrix.

Digital variable frequency oscillator

Abstract: A plural oscillator system with all the characteristics of an analog or variable frequency oscillator, but with the added capability of locking digitally to any frequency within its range. The system has two modes of operation, unlocked and locked. In the unlocked mode, the system employs a variable frequency oscillator together with a reference oscillator and counter to produce the system output and to log the period of the variable frequency oscillator into a memory. In the locked mode, the contents of the memory are held constant, and the variable frequency oscillator no longer drives the system output. Instead, the reference oscillator and counter are used in conjunction with a digital comparator to produce the system output with a frequency determined by the contents of the memory. Thus, the system in the locked mode operates as a digital oscillator at the frequency that the variable frequency oscillator operated before the mode change.

An Instrument for Measuring Betatron Resonant Frequencies

Abstract: An instrument has been developed to measure betatron tunes with a minimum of disturbance to normal operation. In one mode of operation, the beam is driven by a frequency sweeping voltage controlled oscillator (VCO). The output of this VCO is compared to (1-?) feedback from the beam in a phase-sensitive demodulator. The dc output of this demodulator helps to control the frequency of the VCO, thus closing a loop around the beam. At frequency coincidence between the (1-?) feedback and the VCO, a pulse is generated which stops the VCO frequency sweep and allows phase lock on the beam if desired. This pulse also activates measuring and digitizing circuitry to record pertinent data at the instant of frequency coincidence. Other modes of operation permit measurement of, and phase lock to, unexcited or "natural" resonances.

Automatic frequency controlled oscillators

Abstract: Automatic frequency control means for oscillator arrangement of modulatable frequency wherein signals from the oscillator, and signals from a reference source are compared in a comparator which produces signals dependent on the frequency difference of the oscillator and the reference at one or other of two outputs, in dependence upon the sense of said difference. The signals from the comparator drive a circuit which produces a frequency controlling signal which is fed to the oscillator.

Electronic musical instrument master oscillator with provision for frequency control

Abstract: A master oscillator operating in the MHz range for supplying a signal suitable for providing the notes of the musical scale, the various note signals being arrived at by frequency division of the master frequency. The oscillator has a high order of frequency stability together with ease of control for shifting the frequency to supply vibrato, portamento, trill, transposition features and the like. Control is exercised by incorporating a voltage-variable capacitance diode, ''''Varicap,'''' as an effective element in the oscillator tank and varying the diode bias. Features provide for isolation of the bias voltage from the main tank circuit, a zero-bias condition at the true frequency, and a novel comparison tuning system using a slightly off-pitch tuning reference standard for obtaining true pitch.

Amplitude stabilized complementary transistor oscillator

Abstract: Part of the output of a push pull Clapp oscillator is rectified and smoothed to provide a voltage for stabilizing the oscillation amplitude, the control voltage being fed to the base of a transistor that acts as a variable resistance in a voltage divider connected to the bases of the push pull oscillator transistors, the controlled conduction of the voltage divider transistor acting to control the working points of the oscillator transistors so as to maintain a substantially constant oscillation amplitude.

Voltage controlled oscillator multiplier

Abstract: A voltage controlled oscillator and varactor multiplier circuit having a varactor network coupling the output of an oscillator through a band pass filter to an output in which a single varactor produces frequencies tuned by varying the bias thereon and produces frequency multiplication.

Dual-mode phase-locked loop with dead zone phase detector

Abstract: A timing circuit generates the timing signal used in the regeneration of a pulse code modulation signal which contains a timing burst between each word. This is accomplished by synchronizing a voltage-controlled oscillator (VCO) to the timing burst with a dual-mode phase-locked loop. One loop contains a phase detector with a dead zone, which compares the VCO output with a burst detector signal. This phase detector produces an error signal only until the frequencies of the two signals are the same and their phases are within a prescribed range of each other. The other loop contains a gated phase detector which compares the VCO output to the timing burst and produces a second error signal which is combined with the first to control the VCO.