Showing papers on "Frequency drift published in 1971"
•
01 Jun 1971
TL;DR: In this paper, a dual frequency radiometer concept is proposed for detecting metal in the presence of background of normal terrain features, including vegetation, ground soil and water, where the output of each sensing head is mixed with a respective locally generated signal f1 and f2 to produce a common IF frequency and alternately applied to an IF channel.
Abstract: Disclosed is a dual frequency radiometer concept whereby selection of operating frequencies allows the detection and discrimination of metal, water, tarmac, concrete and wet soil from natural terrain backgrounds. Disclosed is one radiometry system designed to detect metal in the presence of background of normal terrain features, including vegetation, ground soil and water. Embodiments of the system are disclosed, employing two radiometer sensing heads operating at different preselected frequencies. The output of each sensing head is mixed with a respective locally generated signal f1 and f2 to produce a common IF frequency and alternately applied to an IF channel. The output of the IF channel is synchronously detected and the difference in level of radiometric energy at the two frequencies is synchronously detected and integrated to produce a difference signal indicative of the presence or absence of metal in the field of view. In one embodiment, the local frequency sources are klystron oscillators and in the second embodiment, solid state Gunn diodes are used. The physical embodiment of one preferred form of sensing head is disclosed. One third embodiment employs a single oscillator and multiplier to produce a second harmonic frequency. The fundamental and the second harmonic are used to serve as reference for the two superhet signal channels. Gain drift, frequency drift and oscillator noise cancellation are all achieved in this embodiment.
31 citations
••
TL;DR: In this paper, a voltage tunable quartz crystal oscillator is proposed, which can be electrically tuned over a frequency range on the order of ± 0.3 percent of the crystal frequency.
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.
31 citations
•
15 Dec 1971TL;DR: In this article, 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 by variable voltages or variable width pulses, proportional to the difference in phase between the two signals.
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.
28 citations
•
17 Sep 1971
TL;DR: In this paper, 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, and after frequency lock the output of the discriminator is nulled and a phase detector becomes effective to maintain phase lock.
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.
20 citations
•
20 Sep 1971TL;DR: In this paper, a controllable broadband frequency generator comprising a voltage-controlled oscillator incorporated in a frequency controlled loop and an external voltage source connected thereto, the control loop furthermore incorporating a digital crystal stable frequency discriminator and a combination device.
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.
20 citations
•
01 Nov 1971
TL;DR: In this paper, a reference signal frequency is generated for selection of a desired channel by a frequency sweep circuit comprising two sweep oscillators, which are reversed with each other at a predetermined frequency interval.
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.
18 citations
•
01 Mar 1971TL;DR: In this article, the authors use additional modulators connected to the carrier oscillators to reduce the frequency offset of the transmitted signal to the frequency variations of only a single oscillator.
Abstract: The terminals in the frequency division multiplexed systems of the prior art employ many steps of modulation whose frequency variations, due to changes in the frequencies generated by the carrier oscillators, add to produce a frequency offset which is unacceptable in modern wideband systems. The terminals of the present invention use additional modulators connected to the carrier oscillators to reduce the frequency offset of the transmitted signal to the frequency variations of only a single oscillator.
16 citations
•
30 Mar 1971
TL;DR: An inverter circuit utilizing a saturable core driving transformer to drive the switch elements includes a generator to pass a stabilized frequency square wave to the driving transformer, which stabilizes the switching frequency of the inverter to match the stabilized frequency of a square wave as mentioned in this paper.
Abstract: An inverter circuit utilizing a saturable core driving transformer to drive the switch elements includes a generator to pass a stabilized frequency square wave to the driving transformer to stabilize the switching frequency of the inverter to match the stabilized frequency of the square wave. Additional switch means coupled to the driving transformer are responsive to the square wave to short circuit, alternately, portions of the driving transformer at points in time at which the square wave changes polarity thereby forcing the flux to reverse and prevent any frequency drift should the feedback current from the output transformer of the inverter exceed the current supplied by the square wave signal. The additional switches also serve to hold the inverter in an off condition by turning both switches on simultaneously.
14 citations
•
19 Nov 1971TL;DR: In this article, the output pulses from a monostable multivibrator coupled to a variable frequency oscillator were compared to the output from a single-input single-output (SISO) multi-channel (MISO) coupled to the VF oscillator.
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.
12 citations
•
23 Dec 1971TL;DR: In this article, a crystal controlled oscillator is used to change the amount of capacitance of a tank circuit in the oscillator causing the frequency of a signal provided by the oscillators to change.
Abstract: A transmitter, including a crystal controlled oscillator, has a pair of three-sided plates mounted on diagonally opposite corners of a rectangular dielectric body. When placed in an electrostatic field, a static voltage is developed across the plates corresponding to the strength of the electrostatic field. The developed voltage is used to change the amount of capacitance of a tank circuit in the oscillator causing the frequency of a signal provided by the oscillator to change. The signal from the oscillator is transmitted to a receiver which may be remotely located from the electrostatic field. The receiver includes a beat oscillator providing a reference signal having the same frequency as the signal induced by the crystal. A detector compares the frequencies of the reference signal and the received signal to provide a signal having a frequency which is the difference in frequency between the received signal and the reference signal. The frequency of the signal from the detector corresponds to the strength of the electrostatic field. The signal from the detector is applied to an output device, such as a loudspeaker or a meter.
10 citations
•
08 Mar 1971
TL;DR: In this paper, 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.
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.
•
06 Apr 1971
TL;DR: 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 oscillators and the reference at one or other of two outputs, in dependence upon the sense of said difference.
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.
•
11 Jan 1971
TL;DR: In this article, 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.
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.
•
01 Jun 1971
TL;DR: In this paper, a two-stage shift register with an inverted feedback loop is used to produce output signals with a phase shift equal to the corresponding fraction of 360* in the frequency domain.
Abstract: A pulse voltage controlled oscillator running at four times the desired frequency f triggers a two stage shift register which has an inverted feedback loop. The outputs of both stages are similar square waves of frequency f, and they are set at a 90* phase difference of each other. Since a square wave of frequency f possesses only harmonics of odd orders, a low pass filter which rejects 3f can admit a square wave frequency varying between f and 3f. A pair of identical filters coupled to the outputs of respective shift register stages provide output signals of corresponding frequency which are 90* out of phase. For a frequency range extending between 3f and 9f, another pair of filters are required, etc. Additional shift registers may be added to the two stage shift register to provide output signals with a phase shift equal to the corresponding fraction of 360*.
•
18 May 1971TL;DR: In this article, the authors describe a means of shifting the frequency of the horizontal oscillator of a television receiver in the presence of high voltage increases which could cause X-radiation problems.
Abstract: Concurrently filed United States Patent application Ser. No. 144,457, entitled ''''HORIZONTAL OSCILLATOR DISABLING CIRCUIT'''' describes a means of shifting the frequency of the horizontal oscillator of a television receiver in the presence of high voltage increases which could cause X-radiation problems. As therein described, a negative direct voltage indicative of the developed ultor potential for its cathode-ray tube is combined with a relatively stable positive direct voltage to change the bias on a control transistor and the effective resistance in the time constant network determining the oscillator frequency. The present invention provides a further positive direct voltage to the transistor from the brightness control network of the receiver, so as to control the point at which the oscillator goes off frequency as a function of picture tube beam current. Such further voltage will be seen to reduce the criticality in determining the point at which the frequency shifting is to occur and the point at which the reproduced picture becomes unviewable.
•
07 Apr 1971TL;DR: In this article, a phase-locked loop including a controlled oscillator having a variable frequency output which is compared in a phase comparator with the received command signal is used to switch the oscillator from its quiescent frequency to the incoming frequency and phase lock it to the command signal.
Abstract: A remote control receiver selectively responsive to a plurality of different frequency command signals to control corresponding different command functions. The receiver uses a phase locked loop including a controlled oscillator having a variable frequency output which is compared in a phase comparator with the received command signal. The detected phase difference generates an error voltage which shifts the oscillator from its quiescent frequency to the incoming frequency and phase locks the controlled oscillator to the command signal. The error voltage also activates only one of several DC voltage comparators, with a different comparator corresponding to each command function. Each comparator includes a means of establishing a reference voltage and means for activating a driver stage for the corresponding remote function when the error voltage generated by the phase comparator to lock the receiver to a particular command frequency and equals the corresponding reference voltage.
•
11 Jan 1971
TL;DR: In this paper, a frequency synthesizer for producing selected frequencies to support an associated receiver is described. But the synthesizer comprises means to generate a discrete frequency signal and generating circuit means adapted to derive from the signal a plurality of signals of different frequencies, and a circuit means is further provided and made responsive to a selection mechanism whereby desired synthesized frequencies are rapidly selected by mixing and dividing the signals of the different frequencies.
Abstract: A frequency synthesizer for producing selected frequencies to support an associated receiver. The synthesizer comprises means to generate a discrete frequency signal and generating circuit means adapted to derive from said discrete frequency signal a plurality of signals of different frequencies. A circuit means is further provided and made responsive to a selection mechanism whereby desired synthesized frequencies are rapidly selected by mixing and dividing the signals of different frequencies. A voltage controlled oscillator and phaselock means reduce the frequency selection response time to provide a substantially exact output frequency. The selection mechanism further controls the bias voltage of the voltage controlled oscillator to approximately tune it to the required output frequency.
•
29 Jun 1971
TL;DR: In this paper, a signal-seeking tuning control system for use with a voltage-controlled tuner is presented, where a ramp generator is operated manually to cause the tuner to sweep through a spectrum of channel frequencies.
Abstract: A signal-seeking tuning control system for use with a voltagecontrolled tuner. A ramp generator is operated manually to cause the tuner to sweep through a spectrum of channel frequencies. When the converted-frequency signal outputted by the tuner approaches a desired frequency range a discriminator produces an error signal for energizing a control system having three discrete states. when the discriminator output is within a fixed, narrowly defined range the control system arrests the operation of the ramp generator. Should the converted frequency drift beyond the narrow range, the discriminator produces an error signal which reflects the change in frequency, energizing an appropriate segment of the control to operate the ramp generator. Retrace means are provided for recycling the ramp generator when the voltage outputted thereby achieves a predetermined maximum or minimum value.
•
05 Aug 1971TL;DR: In this paper, a phase-locked oscillator was proposed for locking to a train of pulse signals where the pulse repetition rates are integer multiples of each other, and the output signal of the bandpass circuit is a sinusoidal signal directed to the gated or multiplier phase detector.
Abstract: A phase locked oscillator for locking to a train of pulse signals where the pulse repetition rates are integer multiples of each other. The input pulse signals are directed to a bandpass circuit, a tuned amplifier, the center frequency of which is selected to be the same as the reference frequency of a phase detector. The output signal of the bandpass circuit is a sinusoidal signal directed to the gated or multiplier phase detector. A square wave voltage controlled oscillator has a portion of its output signal fed back to the phase detector. The output of the phase detector controls the frequency of the voltage controlled oscillator. In the phase locked loop, the square wave voltage controlled oscillator is locked to a reference frequency from the bandpass circuit independent of an integer change in the pulse repetition rate of the input pulse train signals.
•
12 Mar 1971
TL;DR: In this paper, a wide range oscillator which can operate over approximately a 104 GHz frequency range was proposed, which uses a current controlled ramp generator which varies the charging rate of an integrating capacitor.
Abstract: A wide range oscillator which can operate over approximately a 104 frequency range. The oscillator uses a current controlled ramp generator which varies the charging rate of an integrating capacitor. The wide range of charging current plus a low discharge time of the integrating capacitor combines to enable a very wide frequency range oscillator.
•
28 Sep 1971TL;DR: In this paper, the authors propose a frequency control-arrangement for stabilizing the frequency of an oscillator having a controllable frequency on a control-signal, in which a phase discriminator receives the control signal and a comparison signal derived from the oscillator.
Abstract: A frequency control-arrangement for stabilizing the frequency of an oscillator having a controllable frequency on the frequency of a control-signal, in which a phase discriminator receives the control-signal and a comparison signal derived from the oscillator, said oscillator having a frequency control-input. A transmission path connects the phase discriminator to the frequency control-input of the oscillator. The frequency control-arrangement include a storage element, storage control means for storing a voltage derived from the output side of the transmission path in the storage element and means for feeding back a voltage derived from the storage element to the input side of the transmission path.
•
25 Aug 1971TL;DR: A frequency band shifter for shifting a selected frequency band in a complex waveform, which frequency band is translated with its relative frequency, phase and amplitude relationships maintained to a reproduced lower frequency and, if desired, to a smaller frequency band for analysis, is processed by manual or digital control with a master local oscillator control clock that provides protection against drift in frequency and phase throughout the system as mentioned in this paper.
Abstract: A frequency band shifter for shifting a selected frequency band in a complex waveform, which frequency band is translated with its relative frequency, phase and amplitude relationships maintained to a reproduced lower frequency and, if desired, to a smaller frequency band for analysis, which translation is processed by manual or digital control with a master local oscillator control clock that provides protection against drift in frequency and phase throughout the system.
•
NEC1
TL;DR: An automatic frequency control for a crystal tuned oscillator, comprising temperature sensitive means producing an output voltage varying in magnitude over a predetermined environmental frequency range, and series diodes and capacitors or inductors to compensate for the oscillator output frequency deviation as discussed by the authors.
Abstract: An automatic frequency control for a crystal tuned oscillator, comprising temperature sensitive means producing an output voltage varying in magnitude over a predetermined environmental frequency range, a crystal oscillator activated by the temperature means varying output voltage to provide a corresponding output frequency deviation over the predetermined environmental frequency range, and series diodes and capacitors or inductors to compensate for the oscillator output frequency deviation, wherein the diodes are biassed to OFF states by different amounts of voltage to disconnect the capacitors or inductors from the crystal when the temperature means output voltage is less than the biasing voltage smallest amount and further wherein the diodes are activated in turn to ON states to connect the capacitors or inductors in turn with the crystal to maintain the oscillator output frequency deviation at substantially zero value over the predetermined environmental frequency range.
••
TL;DR: In this article, a powerful X band oscillator was reported, with a frequency stability comparable to a quartz clock of high quality, which was realized by coupling externally a standard reflex klystron 2K 25 to a high-Q factor (108) superconducting cavity.
Abstract: A powerful X band oscillator is reported, with a frequency stability comparable to a quartz clock of high quality. It is realised by coupling externally a standard reflex klystron 2K 25 to a high-Q factor (108) superconducting cavity. The observed frequency standard deviations in one second (10?10 in relative value) are in accordance with the theory.
•
10 Nov 1971
TL;DR: In this paper, a frequency control system for controlling the output frequency of a variable frequency oscillator in accordance with a reference oscillator is presented. And the control system can be formed as a single module unit using presently available integrated circuit chips for certain portions thereof and suitable external circuit elements in combination therewith.
Abstract: A frequency control system for controlling the output frequency of a variable frequency oscillator in accordance with a reference oscillator wherein the variable frequency oscillator and reference frequency oscillator signals are converted to pulsed form and their phases are compared to provide a phase difference signal in digital form. The phase difference signal is converted to analog form and filtered by a low-pass filter having a selected transfer characteristic to provide a phase control signal for controlling the operation of the variable frequency oscillator. The control system for producing the phase control signal can be formed as a single module unit using presently available integrated circuit chips for certain portions thereof and suitable external circuit elements in combination therewith.
•
•
25 Aug 1971
TL;DR: A burst control circuit for producing a continuous signal synchronized in phase with an intermittent burst signal and comprising a voltage-responsive control oscillator having a natural oscillation frequency is described in this paper.
Abstract: A burst control circuit for producing a continuous signal synchronized in phase with an intermittent burst signal and comprising a voltage-responsive control oscillator having a natural oscillation frequency, means for comparing the frequency the continous signal with the natural oscillation frequency of the control oscillator and means responsive to the output from the comparing means for producing an error signal and applying it to the oscillator to make equal the natural frequency of oscillation of the control oscillator with the continous signal.
•
21 Jul 1971
TL;DR: In this article, a variable frequency generator utilizing a coulometer for generating a signal having an amplitude that varies in accordance with the integral of a selected function is presented, where a DC current source and an oscillator are connected to the input terminals of the coulometers.
Abstract: A variable frequency generator utilizing a coulometer for generating a signal having an amplitude that varies in accordance with the integral of a selected function. A DC current source and a variable frequency interrogation oscillator are connected to the input terminals of a coulometer which modulates the output of the oscillator in accordance with the integral of the current from the current source. The output of the coulometer is amplified by an AC amplifier and is then demodulated by a standard envelope detector. The demodulated signal is fed back to the oscillator to proportionally control the frequency of the oscillator, that is, as the amplitude of the modulated signal increases, the frequency of the oscillator increases and, as the amplitude of the demodulated signal decreases, the frequency of the oscillator decreases.
•
18 May 1971TL;DR: In this paper, high voltage protection circuits which change the frequency of the horizontal oscillator of a television receiver in response to an indication of increase in the ultor potential developed for its picture tube which could cause danger of X-radiation were disclosed.
Abstract: Pending U.S. Pat. Applications Ser. Nos. 103,713 and 121,250 disclose high voltage protection circuits which change the frequency of the horizontal oscillator of a television receiver in response to an indication of increase in the ultor potential developed for its picture tube which could cause danger of X-radiation. Whereas the circuits of such disclosures operate to change a voltage in the horizontal oscillator to which a capacitor is required to charge in establishing the oscillator frequency, the circuit of the instant invention operates to vary a resistance which, together with a capacitor of this type, sets the time constant which determines such frequency.
••
TL;DR: In this article, the authors investigated the frequency dependence of the efficiency of the modulation of a continuous-wave GaAs laser by varying the injection current and found that this efficiency decreased by a factor of 30 when the modulation frequency was increased from 5 to 200 kHz.
Abstract: The emission frequency of a continuous-wave GaAs laser was modulated by varying the injection current. The frequency dependence of the efficiency of the modulation (the ratio of the amplitude of the frequency oscillations to the amplitude of the current oscillations) was investigated by a new method. It was found that this efficiency decreased by a factor of 30 when the modulation frequency was increased from 5 to 200 kHz. The experimental results were in agreement with the calculation of the temperature dependence of the frequency and of the thermal conditions in the laser.