Showing papers on "Voltage-controlled oscillator published in 1975"

RF signal generator

Abstract: An RF test signal generator including a driving oscillator, a pulse generr for generating narrow spikes at the oscillator frequency (such as a step recovery diode), a modulator and an attenuator. Since the very narrow pulse exhibits nearly constant amplitude in the frequency domain, a constant amplitude comb spectrum with frequency spacing at the oscillator frequency is generated so as to facilitate automated testing techniques.

Fm rf signal generator using step recovery diode

Abstract: A step recovery diode pulse generator is driven by a fixed frequency oscitor to provide pulses which are modulated in a balanced modulator by means of a voltage controlled oscillator controlled by a variable frequency input. The output of the balanced modulator is attenuated and provides a frequency modulated RF signal output.

Multichannel signal transmitting and receiving apparatus

Abstract: A multichannel signal transmitting and receiving apparatus comprises a single reference local oscillator, a phase locked loop including a phase comparator receiving as one input a signal resulting from a frequency division of the output of the local oscillator and a voltage controlled oscillator, a frequency divider for supplying the output of the voltage controlled oscillator as another input to the phase comparator, a circuit for heterodyning a signal received through an antenna with the oscillation outputs of the voltage controlled oscillator and the local oscillator and thereafter detecting the signal thus heterodyned thereby to obtain an audio signal, a frequency converter for obtaining a carrier wave for signal transmission from the oscillation outputs of the local oscillator and the voltage controlled oscillator, a circuit for modulating the carrier wave thus obtained with the audio signal and transmitting the modulated signal through the antenna, a circuit for controllably changing over the oscillation frequency of the local oscillator between different values respectively for signal reception and signal transmission, and a circuit for so controllably changing over the frequency division ratio of the frequency divider between different values respectively for signal transmission and signal reception for each of a plurality of channels. The single local oscillator is used for both signal reception and signal transmission. The frequency converter is provided outside of the loop of the phase locked loop.

Blood pumping system

Abstract: A blood pumping system has a pair of integral flexible bodies each provided with an inlet and an outlet and disposed in open top cavities in a housing. The cavities have extensions holding inlet valves and outlet valves for opening and closing the inlets and outlets. A flexible diaphragm overlies the cavities and their extensions and is secured by a cover providing separate chambers over the inlet valves, the outlet valves and the bodies. Solenoid air valves are selectively energized to supply and exhaust the chambers to operate the valves and bodies. Switches responsive to the full and empty positions of the bodies govern the energization of the solenoids through control circuitry including a voltage controlled oscillator, a device for changing the frequency of the oscillator in accordance with the time of operation of at least some of the switches, and a device for ensuring at least a minimum rate of operation of the switches. Alarms are afforded after a predetermined number of switch operations have been missed.

Frequency synthesizer of the phase lock loop type

Abstract: A frequency synthesizer of the phase lock loop type including a reference frequency source, a voltage-controlled oscillator and a frequency divider connected to the oscillator output to divide the output frequency by a selectively-variable integer N. The outputs of the frequency divider and the reference frequency source are applied to a phase comparator which has an output connected to a filter. The filter output is applied through a multiplier, having a multiplication factor n proportional to N, to the input of the voltage controlled oscillator. The frequency divider and the multiplier are controlled by the same control means in order to keep the loop gain constant, irrespective of the amount of change in N.

A highly stable VCO for application in monolithic phase-locked loops

Abstract: The characteristics of the voltage-controlled oscillator (VCO) are generally the most important in determining the overall system performance of phase-locked loops. A new VCO is described which achieves a better combination of temperature stability, speed, and power dissipation than could previously be obtained in a monolithic integrated circuit.

Phase locked loop with circuit for preventing sidelock

Abstract: A side lock detector to prevent side lock in coherent PSK demodulation. For demodulation purposes it is necessary to recreate the carrier at the receiver. This may be accomplished with a phase-locked loop. However, with plural phase PSK modulation the input signal to the phase-locked loop has energy at side bands spaced at modulation rate intervals from the desired lock frequency as well as at the desired lock frequency. To detect side band lock, a band pass filter monitors the phase detector output of the phase-locked loop. The center frequency of the filter is equal to the modulation rate and the filter band width is very narrow. Only during side lock will significant amounts of energy pass the filter. This energy may be detected by a simple diode detector or the like. A lock inhibit means is provided, responsive to the output of the detector, to drive the voltage controlled oscillator out of a side lock condition.

Traffic radar and apparatus therefor

Abstract: Apparatus is provided for determining the frequency of unknown periodic input signals and primarily generally sinusoidal signals which may be accompanied by very substantial noise. More particularly, the system for determining the frequency of unknown periodic input signals accompanied by substantial noise is adapted to a unique traffic radar or doppler radar system. The apparatus includes a phase locked loop in which the incoming signal accompanied by noise is compared with the output from a voltage controlled oscillator to generate a synthetic signal which is substantially free of noise and is well adapted for counting, measuring and display circuitry to give a direct indication of the input signal frequency or a parameter directly related to that input signal frequency. Specifically in doppler radar systems the direct readout is in "miles per hour", a direct function of doppler frequency. The signal which is being subjected to frequency determination is applied directly to the comparator portion of the phase locked loop circuit and it is also applied to the comparator portion of the phase locked loop circuit through a tunable band pass filter whereby speed of response is obtained without loss of noise rejection or frequency or harmonic range. Also an automatic frequency control loop is employed with the comparator to adjust the voltage control oscillator and this AFC loop has adjustable gain which is directly related to the frequency of the incoming signal to enhance the stability over the entire frequency range. The system is also capable of an instantaneous determination of locked operation whereby false readings are avoided.

Sonic transducer and drive circuit

Abstract: A sonic transducer, having a drive electromechanical transducing element and a pickup electromechanical transducing element or a single transducing element electronically operating as both, is excited through suitable power amplifiers by a voltage controlled oscillator. A phase comparator connected to these transducing elements detects the phase difference between stress and strain in the transducer. Its output is connected to an integrator circuit means which integrates the phase difference signal and applies the integrated signal to control the voltage controlled oscillator. The maximum and minimum values of the voltage which is applied to control the oscillator are independently limited by a pair of diodes connected to sources of two different voltages. An adjustably fixable phase shift circuit is interposed between the pickup transducing element and the phase comparator to permit calibration of the system for optimal operation. Amplifier and clipper circuitry interposed between the phase shift circuit and the phase comparator circuit make the oscillator output signal independent of the amplitude of the vibrations of the sonic transducer.

Electronic tuning control system for television

Abstract: A fine tunable electronic channel select system for controlling the varactor tuner of a television receiver or the like and including a dual mode prescaler for dividing the local oscillator (VCO) frequency of the tuner by a first divisor and then by a second divisor to produce a selectively variable average divide during a sample period, a programmable digital divider for dividing the output of the prescaler by a predetermined divisor corresponding to a selected television channel, a channel selection mechanism for controlling the programmable divider, a signal source for generating a stable reference frequency, a frequency/phase comparator for comparing the output of the programmable divider with the reference signal to develop an error signal, an integrator/amplifier for integrating the error signal to develop a biasing signal for controlling the tuner, and a fine-tune control circuit for selectively controlling the length of time the prescaler operates in each of its two modes, thereby enabling incremental variation of the biasing signal to provide fine tuning of the varactor tuner.

Phase locked loop NRZ data repeater

Abstract: A phase locked loop repeater for reshaping a non-return to zero (NRZ) data stream. A transition detector receives the input data stream from a coaxial cable in a degraded condition in terms of amplitude and phase distortion and produces reference pulses whose positions are very nearly independent of the direction of the transition of the input data. These reference pulses, along with clock pulses from a voltage controlled oscillator (VCO), are applied to a phase comparator and when these signals differ in phase, a voltage is developed for modifying the frequency of the VCO. The clock signals from the VCO are applied to the clock input of a D-type (edge triggered) flip-flop, to which is also applied the incoming data stream. The D-type flip-flop changes state in accordance with the incoming data only at the leading or trailing edge of the clock pulses. As such, the timing and amplitude of the data stream is reconstructed for reapplication and further transmission on said coaxial cable.

Direct reading reactance meter

Abstract: Apparatus for producing an indication of the value of an unknown capacitance or inductance, which employs a variable frequency oscillator producing a sinusoidal output which is fed through a resonant circuit comprising a reactive circuit element of known value selected to attain resonance with the unknown reactor within the oscillator frequency range. A phase detector measures the phase shift between oscillator output voltage and output current, and its direction and supplies a phase shift signal specifying this information to a controller which supplies a frequency control signal to the oscillator. The controller varies the frequency control signal responsive to the phase shift signal to eventually reduce phase shift to 0° or other predetermined value indicating the resonance condition in the circuit. In a preferred embodiment, a series resonance circuit is formed by the known and unknown reactors, and phase shift between oscillator voltage and current is detected by measuring the phase angle of the voltage across the oscillator with respect to that across the capacitor in the series circuit, which angle must be 90° at resonance. This embodiment is particularly well suited to measurement of small inductances in circuits having an appreciable amount of DC resistance.

Phase locked loop resolver to digital converter

Abstract: A resolver-to-digital converter where a signal of predetermined frequency is converted to a given waveform sequence by a logic circuit, band passed filtered, and phase splitted into orthogonal components. These components are fed to operational amplifiers and then into the input windings of a resolver. The outputs of the resolver are fed to a pair of zero crossing differential comparators and then to phase detectors, the outputs of which are summed. The sum of the signals is filtered and is used to regulate a voltage controlled oscillator that pulses a synchronous counter that is fed back to the phase detectors forming a phase-locked loop. The synchronous counter feeds a serial register that is strobed by the output of a zero crossing differential amplifier fed by the compensation windings of the resolver.

Phase locked loop with pre-set and squelch

Abstract: A phase locked loop with pre-set and squelch capability particularly adapted for burst type signals. In addition to the conventional phase detector, loop filter (LF) and voltage controlled oscillator (VCO) the loop includes a squelch switch connected between the phase detector and LF. A track and hold circuit is connected in series with another switch between output and input of the LF. Both switches and the track and hold circuit itself are controlled by the output of a level detector which indicates presence of an intermittent (i.e., bursty) carrier. The squelch switch is closed, connecting the phase detector to the LF, when the output of the level detector indicates the presence of a carrier burst. At the same time, the second switch is opened so that the LF is not affected by the output of the track and hold circuit. In addition, the track and hold circuit is enabled to track the error voltage output of the LF. At the conclusion of a burst the squelch switch is opened so that the noisy output of the phase detector will not affect the LF. In addition, the second switch is closed to allow the output of the track and hold circuit to reach the LF and finally, the track and hold circuit holds the previous error voltage output of the LF. Thus the error voltage, at the conclusion of the carrier burst, is provided by the track and hold circuit to the LF to maintain the VCO at the last known carrier frequency.

Frequency modulated oscillator

Abstract: A frequency modulated push-pull oscillator in which the non-linear characteristic of varactors producing frequency modulation is compensated for by an opposite non-linear characteristic of a field effect transistor (FET) providing modulating bias to the varactors.

Multi-phase PSK demodulator

Abstract: A synchronized carrier recovery circuit for a PSK modulated signal includes a plurality of phase detectors supplied with the PSK input signal and phase shifted outputs from a voltage controlled oscillator. The detector outputs are rectified and alternately coupled to a pair of adders whose outputs feed a complimentary subtractor. The detector outputs are also converted to digital form and fed to an Exclusive OR circuit, whose output couples the appropriate subtractor outputs to the VCO to achieve phase locked synchronization.

Hybrid tracking loop for detecting phase shift keyed signals

Abstract: A hybrid tracking loop detector system that accurately demodulates phase ft keyed acoustic telemetry signals. The system internally determines the received carrier frequency and detects phase shifts that denote the digital format depicted by the phase shift keyed signals. The system is particularly useful for operating at low signal to noise ratios and with relatively short messages. The detector includes a phase lock loop comprising a phase comparator, an amplifier, an adjustable filter and a voltage controlled oscillator. The phase and frequency of the oscillator are divided and are locked to the carrier frequency of the received signal and are used as a reference for the phase comparison detection. The system has two sequented modes of operation, a direct acquisition mode and a holding mode. The detector switches automatically from the direct acquisition mode to the holding mode. The filter is initially broadband to allow detection of doppler shifted carrier signals and after locking onto the carrier signal it is switched to a narrow bandwidth to permit detection of low signal to noise ratio signals. A switching circuit is also provided to eliminate cycle slipping or loss of lock during periods when there is a phase shift in the received signals.

Digital frequency synthesizer

Abstract: A digital frequency synthesizer includes an oscillator and a variable frequency digital divider, whose divisor N is switchably selected for dividing the oscillator frequency. A counter accumulates a count related to the number of cycles of the divided oscillator frequency occurring in a unit time, with this number being used to set the divisor of a second digital frequency divider. The oscillator frequency is also divided by the second divider, with the resultant signal having a frequency of N Hz.

Semiconductor diode temperature sensing device

Abstract: A temperature sensing device is disclosed in which the temperature sensing element is a semiconductor diode. The reference supply current for the diode is derived from an offset voltage regulator in such a way that power source fluctuations appear as common mode inputs to an operational amplifier. The operational amplifier controls a voltage controlled oscillator. The output pulses of the oscillator are counted over periodic time intervals of predetermined length to produce periodic counts which correlate to temperature. The device is designed in the preferred embodiment for use on commercial alternating current power lines where the length of timing for temperature sensing, the interval between readings and switching between multiple sensors is controlled by the power line frequency.

Turbine flowmeter and components thereof

Abstract: A turbine flowmeter with an unusual radio frequency pick-up and non-magnetic, conductive turbine blades. The pickup includes a coil which is also a part of a tank circuit of an input oscillator. A phase lock loop is then employed which receives, as an input, the output of the input oscillator. When a turbine blade passes the pick-up, the input oscillator undergoes a frequency shift. Circuits connected from the phase lock loop output then produce pulses which are counted and indicated. The circuits may be constructed to cause an indicator to read in units of volume, i.e. the total volume flow through the flowmeter, if desired. The said circuits include two active filters, a Schmitt trigger, a current converter and an output circuit from the phase lock loop output.

Comb filter apparatus for video playback systems

Abstract: Comb filter apparatus for separating interleaved luminance and chrominance components of a composite color video signal employs a clock controlled delay line of the CCD type to which the composite signal is applied. A VCO supplies clock signals to the CCD delay line, and to a frequency divider. The output of the frequency divider is compared in phase with a color synchronizing component of the undelayed composite color video signal to develop an error signal, which is applied to the VCO in a sense opposing departures from a predetermined phase relationship between the divider output and the synchronizing component. Spurious frequency variations of composite signal components (e.g., accompanying recovery of composite signal by playback of a video disc) are followed by the VCO in a manner assuring that accurate combing of the composite signals occurs at the outputs of circuits providing desired combinations of the delay line input and output.

Wideband phase locked loop transmitter system

Abstract: A phase locked loop including a reference oscillator connected to one input of a loop phase detector the output of which is connected through an integrating low pass filter to a voltage controlled oscillator with the output of the voltage controlled oscillator being mixed with a second frequency and compared to the reference in the loop phase detector. The mixer output is also compared to an output of the reference oscillator shifted 90° in a quadrature phase detector, the output of which controls a lock detector which in turn controls a fixed current sink. The fixed current sink is connected to the integrating low pass filter when the loop is in an unlocked condition so that a linear voltage, ramp signal is applied to the voltage controlled oscillator from the output of the integrating low pass filter. An RF gate attenuates the voltage controlled oscillator output until lock is achieved and subsequent power amplifiers are in operation at which time the RF gate gradually connects the power amplifiers to the output of the voltage controlled oscillator.

Local oscillator arrangement for a monopulse receiver in a semiactive missile guidance system

Abstract: An improved local oscillator arrangement for a monopulse receiver in a semiactive missile guidance system is shown. The monopulse receiver includes an improved reference local oscillator wherein a first local oscillator signal and a pair of reference signals required to demodulate the output of the intermediate frequency section of such receiver are derived simultaneously from the output of a single voltage controlled crystal oscillator. The frequencies of the first local oscillator and the pair of reference signals are related to the frequency of the radar modified by any Doppler shift frequency experienced during an intercept.

Phase locked loop tracking filter having enhanced attenuation of unwanted signals

Abstract: In a tracking filter, which includes a conventional phase locked loop having a phase detector, a filter and a voltage controlled oscillator adapted to track a wanted signal and attenuate unwanted signals and noise from an incoming spectrum of signals, there is provided a phase modulator and an additional filter adapted to attenuate further the unwanted signals and the noise without degrading the ability of the loop to track the wanted signal.

Phase locked oscillator

Abstract: In a phase locked oscillator (PLO), the frequency of a voltage controlled oscillator (VCO) is changed in response to error signals indicating the phase error between the individual pulses of a stream of input pulses and the output pulses of the PLO. The running of the PLO is temporarily interrupted whenever the phase error exceeds a predetermined amount, and is restarted in phase with the next input pulse from the stream of pulses. A residual part of the error signal causing the interruption is accumulated so that after each interruption the frequency of the oscillator is closer to the frequency of the input stream of pulses. The process is repeated as required until phase lock is achieved.

Simplified surface acoustic wave synthesizer

Abstract: A highly stable variable frequency oscillator is disclosed which employs aultitap surface acoustic wave device as a frequency standard. A feedback path which includes a voltage controlled switch for selecting a desired output tap drives a differential amplifier, phase detector, low pass filter, voltage controlled oscillator and phase splitter for driving the input tap of the surface acoustic wave device. Various additional feedback paths are also employed. The variable frequency signal is taken from the output of the voltage controlled oscillator.

Phase demodulator with offset frequency reference oscillator

Abstract: A phase-locked demodulator for demodulating a phase-difference modulated carrier having a repeated phase offset increment introduced therein. The demodulator includes, in common with conventional phase locked demodulators, a mixer having a first input connected to receive the modulated carrier and a reference carrier generator such as a voltage controlled oscillator (VCO) connected in a phase-locked feedback loop forming the second input to the mixer. In order to reduce the number of output levels, the VCO is tuned to a frequency Fr=Fc±Fb[(α)/360] where Fc is the carrier frequency, Fb is the baud rate and α is the repeated phase offset. In this way the phase offset increment introduced into the modulated carrier is substantially cancelled out thereby leaving only the phase changes containing data information.

Ink jet with uniform density trace control for recorders

Abstract: A chart recorder is disclosed having a variable chart speed and a writing device in the form of a variable droplet rate ink jet pen. The signal pulses for ejecting ink droplets from the pen are generated by a voltage controlled oscillator, and circuits are provided to make the oscillator output frequency proportional to the chart speed, and also responsive to higher rates of pen movement, so that a substantially uniform density line is traced at all chart speeds and virtually all rates of pen movement. To simplify the circuit while maintaining an extremely wide range of writing speeds, the voltage sweep range of the oscillator is set at the upper end of the pen response frequency, and lower oscillator output rates are established by selectable R-C circuit components to match the speed of the chart recorder. To give more precision, a circuit embodiment is also disclosed that generates pen control pulses proportional to the true rate of relative movement between the pen and the chart. The application of the latter circuit to an X-Y recorder is also disclosed.

Dual-mode waveform generator

Abstract: The disclosed circuit provides a signal generator which is particularly adapted for use as an audible "kilo-sonic" game device in which a plurality of switches are provided so that the different combinations of switch positions produce a corresponding number of different sounds. The circuit includes a voltage-controlled-oscillator (VCO) having an output coupled to a transducer such as a speaker. The VCO is modulated in accordance with a control signal, provided by an up-down staircase generator which is responsive to a pulse generator, to vary the frequency of its output signal. The output of the pulse generator is also selectively coupled with the output of the staircase generator. Time-constant circuits in each of the generators are respectively under the control of selected ones of the switches; and two basic modes of operation are provided by the selected switches so that the control signal at the VCO input is either a pseudo random signal, or a synchronized sub-multiple signal wherein the frequency of the staircase generator output signal is a sub-multiple of the pulse generator output signal. Accordingly, the number of different output sounds provided by the disclosed circuit is geometrically proportional to the number of switches provided.

Voltage controlled oscillator circuit

Abstract: A voltage controlled oscillator circuit comprises a voltage controlled oscillator circuit, first and second constant-current circuits respectively for causing first and second constant currents, current dividing means for dividing the first constant current in accordance with an outside control voltage, and means for adjustably varying the control voltage. The oscillation frequency is controlled responsive to an input control current equal to the sum of one of the divided currents and the second constant current. The adjustment means causes an adjustment of the output currents of the current dividing means and of the free-running oscillation frequency.