Showing papers on "Frequency drift published in 1985"

Tunable, dielectric-resonator-stabilized oscillator and method of tuning same

Abstract: A dielectric-resonator-stabilized, Gallium-Arsenide-FET, negative resistance oscillator operating in the microwave region incorporating an improved form of dielectric resonator whose resonant frequency is tuned by the addition or removal of metal from the surface of a dielectric tuning plate in the resonator, and a method for tuning the oscillator to the desired frequency range with the resonator in place by use of a laser-trimming device are disclosed.

Apparatus and method for frequency modulation

Abstract: A method and apparatus for frequency modulating a continuous wave signal is shown to comprise a voltage-controlled oscillator (VCO) having a first and a second control loop to maintain the carrier frequency of such VCO at a frequency determined by a crystal-controlled oscillator and to maintain the peak deviation of the FM modulation on such carrier frequency at a value equal to the deviation of the first Bessel null from the carrier frequency.

Phase nulling optical gyroscope

Abstract: A gyroscope system includes a coherent light source that supplies counter propagating waves to a sensing loop through a pair of directional couplers. The polarizations of the waves are controlled so that they traverse identical optical paths before recombining in one of the couplers to form an interference pattern. Rotation of the sensing loop, a phase modulator and a frequency shifter cause phase changes in the counter propagating waves. A detector monitors the interference pattern of the combined waves and provides a signal to a coherent demodulator that controls the phase modulator. The output of the coherent demodulator is input to a servo-loop circuit that drives a voltage controlled oscillator. The output of the voltage controlled oscillator is an oscillatory signal having a frequency equal to the shift in frequency that the counter propagating waves experience in traversing the frequency shifter. The feedback circuitry adjusts the frequency shift to null the phase difference between the counter propagating waves. The frequency shift is linearly related to the frequency of the signal output from the voltage controlled oscillator. Each cycle of the output of the voltage controlled oscillator coresponds to a fixed angular increment of displacement of the sensing loop. The rotation rate of the sensing loop is a function of the frequency shift and the transit time of the waves through the sensing loop. The gyroscope system determines rotation rates and angular displacements over a wide dynamic range by measuring the frequency and zero crossings of the oscillatory output of the voltage controlled oscillator.

Tunable notch filter for image frequency and conducted local oscillator leakage rejection

Abstract: A tunable notch filter for the front end of an RF receiver includes magnetically coupled input and output tunable stages each responsive to a tuning voltage provided thereto. Each of the input and output stages includes a respective series and parallel resonant circuit wherein the parallel resonant circuits are tuned to a selected RF frequency and the series resonant circuits are tuned to a frequency approximately equal to that of a local oscillator. By using the series resonant circuits to create a notch at a frequency approximating that of the local oscillator, conducted local oscillator leakage from the receiver's antenna is substantially reduced and local oscillator image frequency rejection is substantially improved.

Method and apparatus for spectral dispersion of the radiated energy from a digital system

Abstract: O Method and apparatus are disclosed for dispersing the electromagnetic energy radiated from a digital system to minimize the EMI and RFI emanating from such a system. To accomplish this, one approach of the present invention includes a VCO which is modulated by a band-limited signal to provide a system clock signal which has a broader spectral signature than the traditional precise crystal controlled oscillator traditionally utilized in digital systems. In addition, an optional feedback stage is disclosed for compensating for frequency drift of the VCO with time. This includes a precision crystal controlled oscillator operating at substantially the same frequency as the unmodulated VCO. This signal is then continuously compared with the modulated output signal of the VCO to generate a compensation signal which in turn is combined with the modulation signal to minimize the long-term errors and thus minimize the long-term drift of the modulated clock signal. Another approach disclosed is to modulate the amplitude of the bus voltage being provided for the digital system.

Magnetic laser control

Abstract: A method and means for stabilizing the difference in frequency between component frequency modes of a gas laser influenced by Zeeman splitting is presented, comprising an electronic servo control loop which drives a magnetic flux element (40) for tuning the frequency separation of the component frequency modes and a thermal element (36) for tuning the length of the lasing chamber. A beat signal (64) obtained from heterodyning the component modes of the laser beam is compared with a reference signal (68) to generate a control signal (74, 78) for driving the flux and thermal elements which determine the difference in frequency between the component frequency modes.

Subscriber unit for a flexible communication system

Abstract: A communication transceiver is described which can permit operation of the transceiver unit in either the trunked dispatch mode or in the cellular mode. The ability to utilize two sets of frequencies with different transmitter channel separation can be accomplished by providing a phase lock loop configuration with a signal having a frequency that is the separation between the transmit channels of the selected communication system or is a fraction thereof. Similarly, a controllable reference oscillator frequency is forced through the phase locked loop configuration, to provide a signal for which a the frequency multiple of the difference frequency for the selected communication mode and is the frequency of the channel. A scaling network provides a signal for the phase lock loop that, for the correct frequency of a controllable oscillator, is the difference between the transmitter or receiver channels. The feedback loop is used to control the controllable oscillator frequency so that the reference frequency establishes the channel difference frequencies for the voltage controlled oscillator. Apparatus is described for retrofitting existing devices to use the two frequencies or for providing a general frequency synthesizing network to accommodate both modes of communication in response to appropriate logic signals.

Improvements in or relating to direct modulation fm data receivers

Abstract: A direct modulation FM data receiver of the offset type in which the local oscillator frequency is located between the two signalling frequencies, deliberately folding the transmitted spectrum about d.c. in order to counter the effects of drift in the local oscillator, the receiver comprises a simple but effective AFC system wherein over the relevant frequency range, it has a non-linear discriminator transfer function and in use produces a voltage having a sign to adjust the local oscillator frequency in the correct direction.

Voltage controlled oscillator with self-adjustment of operating point

Abstract: A voltage controlled oscillator includes automatic adjust circuitry to achieve and maintain desired operating characteristics such that for a predetermined output frequency the oscillator will have a predetermined input voltage. The oscillator may advantageously be incorporated into a phase locked loop circuit. The phase locked loop will lock onto the frequency of an input signal. Automatic adjust circuitry monitors the input to the voltage controlled oscillator in the phase locked loop and varies the amount of a bias voltage applied to the oscillator so that the input voltage to the oscillator will change until it reaches the desired level. The provision of the automatic adjust circuitry enables the desired operating characteristics of the oscillator to be maintained in spite of long term changes in the circuit operation.

High precision tunable oscillator and radar equipped with same

Abstract: A frequency tunable oscillator is associated to a memory (4) which stores the digital values required for controlling the oscillator with a view to obtaining the desired frequency. The digital values are converted by a digital-analog converter into a control voltage for controlling the oscillator (1). The device allows to compensate any non-linear behaviour of the components, as well as the variations of their behaviour with temperature. The present invention is applicable primarily to oscillators generating a frequency which is proportional to a voltage supplied to the oscillator.

The role of long‐term lamp fluctuations in the random walk of frequency behavior of the rubidium frequency standard: A case study

Abstract: A long‐term frequency stability test has been performed on an EGG namely, long‐term frequency drift, spontaneous frequency jumps, and random walk of frequency noise for long averaging times. By careful analyses of the complete test record, we have found that the spontaneous frequency jumps and the random walk of frequency noise can be attributed to the behavior of the clock’s discharge lamp. The long‐term frequency drift, however, was found not to be primarily lamp related. Although results of only a single test on a single Rb clock are reported here, we believe that the results are applicable to the Rb clock technology as a whole.

Dielectric resonator oscillators with digital temperature compensation

Abstract: A digital compensation circuit for improving the temperature stability of dielectric resonator oscillators is disclosed. A temperature sensor indicates a measure of ambient temperature which is correlated with an amount of phase shift necessary to compensate for frequency drift in a dielectric resonator oscillator. The correlation is made using a correction table or correction function which is determined empirically in a calibration process. The necessary phase shift is then supplied via a voltage controlled phase shifter. This phase shifter is part of the RF oscillation loop which also includes an amplifier, directional coupler and dielectric resonator filter (including microstrip).

Voltage controlled oscillator having frequency independent of process parameters

Abstract: A voltage controlled oscillator includes an oscillator having at least one first capacitor. The oscillator receives first and second input voltages and charges the first capacitor with a first current corresponding to the first input voltage. The oscillator oscillates at a frequency corresponding to the first and second input voltages. To remove the adverse influence on the oscillating frequency by the change of process parameters caused in the stage of manufacturing the voltage controlled oscillators, a second capacitor is charged for a predetermined period by a current corresponding to the first voltage. After the charging of the second capacitor ends, a sample/hold circuit samples and holds the charged voltage across the second capacitor. An operational amplifier receives, at its positive input terminal, the output voltage of the sample/hold circuit, and, at its negative input terminal, the reference voltage. The operational amplifier controls the first voltage so that the output signal of the sample/hold circuit will be equal to the reference voltage. Repeating the sequence of the charging, sampling and comparing operations eliminates the influence upon the oscillating frequency by the change of the process parameters caused in the manufacturing stage.

Cardiac output estimation method and apparatus

Abstract: Thermocouple pairs measure the temperatures at a cold-fluid injection point and a downstream point. The reference thermocouple of each pair sees the temperature of a thermally floating heat sink of unknown temperature that has high thermal conductivity and mass, and is well insulated from the environment. Consequently the heat-sink temperature drift is practically constant. To the extent that heat-sink temperature drift is significant, the invention overcomes the effects of drift to a first approximation by providing electronic circuitry that in effect registers the drift in measurement voltage before fluid injection, extrapolates this voltage drift into the measurement time period, and automatically subtracts the extrapolated voltage drift from the measurement voltages.

Millimeter wave frequency synthesizer with automatic loop gain correction and sophisticated lock search systems

Abstract: There is provided an indirect frequency synthesizer in the millimeter wave frequency range of 36 to 38.6 GHz. The synthesizer comprises a high performance frequency translation loop for operation in the microwave frequency range and contains a voltage-controlled oscillator, an automatic loop gain correction system and a sophisticated lock search system. The frequency translation loop is operable under a variety of conditions (temperature etc.) and overcomes the considerable difficulties which exist in this frequency range such as maintenance of constant optimum loop parameters, thus making it possible to utilize the entire frequency tuning range of the millimeter wave oscillator. As a result, the synthesizer has very satisfactory characteristics as regards noise and spurious frequencies products.

Method of and apparatus for generating a frequency modulated ultrahigh frequency radio transmission signal

Abstract: A UHF transmission frequency oscillator generates a UHF radio signal that is frequency modulated by a program signal. The voltage applied to a control voltage input of the UHF transmission frequency oscillator controls the transmission frequency. A sample of the UHF transmission frequency signal is heterodyned with the output of a crystal controlled reference frequency oscillator to generate a frequency difference signal. A voltage controlled VHF radio signal generator produces a VHF signal frequency modulated by the program signal. A phase detector receives the frequency difference signal and the VHF signal frequency modulated by the program signal and therefrom applies a voltage to the control voltage input of the UHF transmission frequency oscillator for the transmission of a UHF radio frequency signal frequency modulated by the program signal. The VHF voltage controlled generator has VHF programmable frequency dividers, which are pre-settable, to establish the VHF radio transmission frequency. The output of the VHF voltage controlled generator is phase locked through the phase detector with the crystal controlled reference oscillator for the stabilizing of the output transmission frequency of the UHF transmission frequency oscillator.

Enhanced frequency determination for spectrum analyzers or the like

Abstract: An arrangement is provided for enhancing the accuracy of frequency determination in a spectrum analyzer or the like having a local oscillator heterodyned with and locked to a frequency comb, by providing a determination of whether the local oscillator frequency is above or below the comb frequency to which it is locked, thereby avoiding ambiguity in the determination of the local oscillator frequency.

AFC circuit for direct modulation FM data receivers

Abstract: An FM data receiver of the offset type, in which the local oscillator frequency is located between the two frequency-shift-keyed signalling frequencies To counter the effects of drift in the local oscillator, a simple AFC system mixes the signalling tone signals with delayed signals to provide a frequency control signal

Receiver for satellite broadcasting service

Abstract: In a receiver for satellite broadcasting service, a selected audio subcarrier is converted into an IF signal demodulated into a demodulated signal which is applied to a feedback voltage generating means which converts the applied signal into a feedback voltage at a voltage ratio corresponding to the maximum frequency deviation of the selected audio subcarrier. The feedback voltage is applied by an operational amplifier to a varactor diode in a voltage-controlled oscillator. The oscillation frequency of the voltage-controlled oscillator is therefore varied dependent on the frequency deviation of the selected audio subcarrier to cause the maximum frequency deviation of the IF signal from a frequency mixer to match the bandwidth of a bandpass filter.

Screened-space-charge transferred-electron oscillators

Abstract: We describe a novel form of a monolithic semiconductor oscillator in which the space-charge field of a drifting charge packet is modified, by means of the electrostatic boundary conditions of the device, so as to produce no voltage drop across the packet. Under these conditions, we predict that a sequence of narrow, identical, contiguous packets can be formed producing extremely high-frequency oscillations in the 30-300-GHz range, independent of the length of the drift region. This is in contrast to conventional transferred-electron oscillators in which the space-charge-induced voltage drop across either an accumulation region or a dipolar domain limits the drift region to, at most, a single packet at any time, thereby limiting the frequency achievable to packet-transit, -formation, or -decay times. Computer simulations and analytical solutions indicate that the frequency can be tuned electronically over a broad band by controlling the charge-injection level, while the oscillator center frequency depends upon the specific device geometry and the electron transport properties at the applied field. In theory, oscillations as high as 2 THz are not inconceivable.

Circuit synchronized by a signal at a deflection frequency

Abstract: A phase-lock loop circuit of a video display apparatus is synchronized by a horizontal synchronizing input signal. The phase-lock loop circuit includes a frequency-to-voltage converter that is responsive to the synchronizing input signal for generating a control voltage indicative of the frequency of the synchronizing input signal. A voltage-to-current converter responsive to the control voltage generates a control current that is indicative of the frequency of the input signal. The control current varies the free running frequency of a controlled oscillator of the phase-lock loop circuit such that the free running frequency of the oscillator is directly related to the frequency of the input signal. The phase of the output signal of the oscillator is controlled by a second control current that is indicative of the phase difference between the oscillator output signal and the synchronizing input signal. When the frequency of the input signal is lower than a predetermined frequency, the first control current is at a level that causes the free running frequency to be above a predetermined minimum frequency.

Temperature sensitive oscillator

Abstract: An oscillator circuit for sensing and indicating temperature by changing oscillator frequency with temperature comprises a programmable operational amplifier which is operated on the roll-off portion of its gain versus frequency curve and has its output directly connected to the inverting input to place the amplifier in a follower configuration Its output is also connected to the non-inverting input by a capacitor with a crystal or other tuned circuit also being connected to the non-inverting input A resistor is connected to the program input of the amplifier to produce a given set current at a given temperature, the set current varying with temperature As the set current changes, the gain-bandwidth of the amplifier changes and, in turn, the reflected capacitance across the crystal changes, thereby providing the desired change in oscillator frequency by pulling the crystal There is no requirement that a crystal employed with this circuit display either a linear frequency change with temperature or a substantial frequency change with temperature

Frequency controlled oscillator utilizing an U/D counter in the feedback

Abstract: A frequency controlled oscillator arranged to be fabricated in integrated circuit form including a primary frequency controlled oscillator and a secondary frequency controlled oscillator with a counter arranged to periodically count pulses of the oscillation frequency of the secondary frequency controlled oscillator and to produce a first output signal if the count is less than a predetermined value and to produce a second output signal if the count is greater than a predetermined value, and control means providing a bias control signal in dependence on the output signals of the counter for tuning the oscillation frequency of both the secondary frequency controlled oscillator and the primary frequency controlled oscillator.

Automatic frequency control for radar receiver

Abstract: A digital automatic frequency control for a pulse-type radar receiver having a voltage controlled local oscillator. A first digital number is generated and converted to a first analog voltage for coarse control of the local oscillator frequency. The first digital number is varied during the time output from the radar transmitter is present at the receiver mixer. The first digital number is varied causing sweep of the local oscillator frequency. When the difference frequency output from the mixer is at a value to cause output from the receiver intermediate frequency amplifier of a predetermined level, variation of the first digital number is halted, providing a coarsely tuned local oscillator frequency. A second digital number is then generated, converted to a second analog voltage which is combined with the first analog voltage. The second digital number is varied to cause the local oscillator frequency to be sidestepped above and below the coarsely tuned frequency. Samples of the receiver output are separately accumulated for sidesteps above and below the coarsely tuned frequency. The difference between the separated accumulated outputs is used to generate a third digital number which is converted to a third analog voltage. The third analog voltage is combined with the first analog voltage to fine tune the local oscillator frequency.

A New Method for Frequency Modulation of Dielectric Resonator Oscillators

Abstract: This paper presents a new method of electronic tuning, i.e. frequency modulation of dielectric resonator oscillators. The method is based on perturbing the field above the dielectric resonator. A preliminary model showed a frequency shift of more than 40MHz at approximately 16GHz, with a keying rate higher than 20Mb/s. Application of analog frequency modulations is also possible.

Detector for indicating frequency deviation peaks

Abstract: A detector for indicating reception disturbances during ultrashort wave broadcast reception by demodulating of intermediate frequency signals has a frequency modulated demodulator with a demodulation characteristic line formed so that a controlling region within which the output signal increases with increasing frequency deviation from a carrier frequency extends advantageously over the entire band width of the ultrashort wave intermediate frequency channel and is significantly greater than the maximum frequency deviation of the intermediate frequency carrier modulated with the basic band signal in the frequency, and the output signal of the frequency demodulator is supplied to an evaluating circuit at whose output the exceeding of a predetermined frequency disturbance deviation threshold is indicated by a logic signal.

Direct FM crystal-controlled oscillator

Abstract: A direct frequency modulation crystal-controlled oscillator circuit is provided having a configuration which minimizes the number of parts required for modulation while maintaining a linear relationship between the incoming modulation voltage and the outputted frequency. The circuit includes a tuning diode (12) in a parallel arrangement with a tank circuit (22) connected to the collector of a transistor (20). In the preferred embodiment, the tank circuit includes only an inductor (24). The crystal (26) of the circuit operates in the anti-resonant mode and its impedance is much greater than that of the tank circuit (22). Direct frequency modulation results from the frequency change of the crystal (26) in responding to a phase change caused by the modulation voltage applied to the tuning diode (12), which subsequently results in a change in the phase of a transistor collector voltage. The desired linear relationship is achieved over a frequency range by prop er selection of the tuning diode (12), wherein the I non-linearity that exists between voltage and capacitance associated with the tuning diode is compensated for by the offsetting non-linearity that exists between capacitance and frequency associated with the tank circuit (22).

Phase-lock loop including integrated circuit voltage controlled oscillator

Abstract: A voltage controlled oscillator (VCO) is described which comprises a plurality of inverter stages of odd number connected in a ring with the output of each stage connected to the input of the next stage via a voltage controlled impedance provided by the transconductance of pass transistors. In one embodiment, this VCO is incorporated into a Phase-Lock Loop circuit, in which the gates of the pass transistors are connected to a control circuit which provides a variable biasing voltage to the gates inresponse to speed-up or slow-down signals provided by a phase detector. The bias on the gates adjusts the frequency of the voltage controlled oscillator, in accordance with the speed-up or slow-down signal. The phase detector is coupled to a stream of input data pulses and to a reference train of clock pulses provided by the voltage controlled oscillator. The phase detector determines whether the frequency of the clock pulses are faster or slower than the frequency of the data pulses and produces either a speed-up signal or a slow-down signal, depending upon the relative speed. These slow-down and speed-up signals are fed to control means responsive to the signals to increase or decrease the bias voltage applied to the gates of the pass transistors.