Showing papers on "Frequency drift published in 1984"

A New Technique for Rapid Tracking of Frequency Deviations Based on Level Crossings

Abstract: A novel frequency computation technique suitable for single or three phase voltage signals is proposed. The method is based on a generalization of the zero crossing detection to a level crossing detection. This yields several estimates of the frequency within one cycle. A composite "best estimatet" is obtained by an appropriate weighted average of these estimates. The method is insensitive to amplitude variations, unbalance and is capable of tracking small frequency deviations in as short a duration as a fraction of a cycle. The measurement scheme is particularily suitable for integration with the digital schemes for real-time monitoring control and protection of power systems.

Flux-flow-type Josephson oscillator for millimeter and submillimeter wave region. II. Modeling

Abstract: A theoretical study is made of a travelling‐wave‐type oscillator, which utilizes a flux flow in a long Josephson junction for use as a local oscillator in the integrated superconducting receiver system. An internal electromagnetic field of the oscillator junction in the flux‐flow state is investigated both numerically and analytically. It is shown that the voltage amplitude of the internal oscillation increases gradually in the direction of the flux flow and reaches a maximum value at the junction end. An equivalent circuit of the oscillator is also obtained, which gives dependences of the emitted radiation on frequency, magnetic field, and load. It is shown that the output power attains the value of the order of 10−6 W in the frequency range between 100 and 500 GHz, and that the output power and the radiation frequency can be controlled by both the bias voltage and the applied magnetic field. These theoretical results explain quantitatively the experimental ones with a Pb‐alloy long junction of length 24 λJ.

Irradiation device for treating living tissue with electro-magnetic waves

Abstract: 1. A radiation device for the treatment of living tissue with electromagnetic waves, with a high frequency oscillator stage (15) for the generation of a high frequency wave train, with a clock generator (19) down-line as a chopper which periodically interrupts the high frequency wave train and with an output amplifier (20) whereto there may be connected a transmitting aerial (13) into whose radiation range there may be positioned the tissue to be treated, or a patient, characterized in that the high frequency oscillator stage (15) produces a frequency which may be set in the range of 100 to 200 Mhz, that provision is made for a low frequency oscillator stage (16) which produces a frequency that may be set within the range of 1 Hz to 1000 Hz that the output of the high frequency oscillator stage (15) and the output of the low frequency oscillator stage (16) are brought together in a modulator unit (17) so that a modulated wave train is generated and that the modulated wave train is passed to the clock generator (19) and that the clock generator (19) may be set to a pulse frequency of 0.5 Hz to 40 Hz.

Tuning of a resonant circuit in a communications receiver

Abstract: A method and apparatus is provided for the tuning of the resonant circuits of a communications receiver. The frequency f D is generated with an additional oscillator, which frequency is then mixed with the receiver oscillator frequency, of which three frequencies fo, fo+f D , fo-f D are formed and are applied to the antenna output. The frequency f D , which is evaluated as a narrow band, is generated by mixing at the intermediate frequency output. A maximum balancing is provided over all high-frequency circuits. The acceptor circuits are tuned to fo and fo+f D (N+5, N+11) for obtaining maximum damping of the oscillator frequency and of the mirror frequency, where N+5 and N+11 represent mirror frequencies.

Clock Characterization Tutorial

Abstract: Managers ar9 often required to make key program decisions based on the performance of some elements of a large system. This paper is intended to assist the manager in this important task in so far as it relates to the proper use of precise and accurate clocks. An intuitive approach will be used to show how a clock’s stability is measured, why it is measured the way i t i s , and why it is described the way it is. 4n intuitive explanation of the meaning of time domain and frequency domain measures as well as why they are used will also be given. Explanations of when an “Allan variance” plot should be used and when it should not be used will also be given. The relationship of the rms time error of a clock to a CI~(T) diagram will also be given. The environmental sensitivities of a clock are often the most important effects determining its performance. Typical environmental parameters of concern and nomj.nsl sensitivity values for commonly used clocks will be reviewed. SYSTEMATIC AND RANDOM DEVIATIONS IN CLOCKS This paper is tutorial in nature with a minimum of mathematics -the goal being to characterize clock behavior. First, time deviations or frequency deviations in clocks may be categorized into two types: systematic deviations and random deviations. The systematic deviations come in a variety of forms. Typical examples are frequency sidebands, diurnal or annual variations in a clock’s behavior, time offset, frequency offset and frequency drift. Figure 1 illustrates some of these. If a clock has a frequency offset, the time deviations will appear as a ramp function. On the other hand, if a clock has a frequency drift, then the resulting time deviations will appear as a quadratic time function --the time deviations will be proportional to the square of the running time. There are many other systematic effects that are very important to consider in understanding a clock’s characteristics and Figure 1 is a very simplistic picture or nominal model of most. precision osci l lators. The random fluctuations or deviations in precision oscillators can often be characterized by power law spectra. In other words, if the time residuals are examined, after removing the systematic effects, one or more of the power law spectra shown in Figure 2 are typically observed. The meaning of power law spectra is that if a Fourier analysis or spectral density analysis is proportional to fB; B designates the particular power law process (8 = 0, -l,-2,-3,-4 and u = 2nf). The first process shown in Figure 2 is called white noise phase modulation (PM)., The noise is typically observed in the short term fluctuations, for example, of an active hydrogen maser for sample times of from one second to about 100 seconds. This noise is also observed In quartz crystal oscillators for sample times in the vicinity of a millisecond and shorter. The f l icker noise P M , f-l, is the second line in Figure 2. This kind of noise is often found for sample times of one millisecond to one second in quartz crystal oscillators. The f-* or random walk PM indicated by the third line is what is observed for the time deviations of rubidium, cesium, or hydrogen frequency standards. If the first difference is taken of a series of discrete time readings from the third line, then the result is proportional to the frequency deviations, which will be an f” process or a white noise frequency modulation (FM) process. In other words the time and the frequency are related through a derivative or an integral depending upon which way one goes. The derivative of the time deviations yields the frequency deviations, and the integral of the frequency deviations yields the time deviations. So, random walk time deviations result from white noise Ft4. In general, the spectral density of the frequency fluctuations is w* times the spectral density of the time flu tuations. The fourth line in Figure 2 is an f-s process. I f this were representative of the time fluctdations then the frequency would be an f-’ or a flicker noise FM process. This process is typical of the output of a quartz crystal oscillator for sample times longer than one second or the output of rubidium or cesium standards in the long term (on the order of a few hours, few days, or few weeks

Frequency detector for use with phase locked loop

Abstract: A frequency detector receiving two input frequencies and generating a pump-up/pump-down signal for control of a phase locked loop by matching the frequency of a voltage controlled oscillator to the frequency. The lock is independent of the phase relationship of the signals.

Dual pilot phase lock loop for radio frequency transmission

Abstract: A radio frequency transmission system contains at least one coherently modulated information signal, for example, a T.V. signal. At a transmission, the information signal is combined with two pilot tones, F1 and F2, related by the equation F1=N/M F2, where N and M are integers. The combined signal is suppressed-carrier modulated at microwave frequencies and transmitted to a receiver. At the receiver, the signals are demodulated by a local oscillator. The two pilot tones are then separated from the information signal and are compared to each other. The local oscillator frequency is controlled in response to this comparison such that the pilot tones at the receiver bear the same relationship to each other that they had at the transmitter. When this is achieved, the local oscillator frequency is the same as the suppressed-carrier frequency and co-channel interference is prevented.

Narrow deviation voltage controlled crystal oscillator

Abstract: A narrow band, voltage controlled crystal oscillator having a linear frequency versus tuning voltage response The oscillator uses a composite resonator in a novel circuit configuration with a resulting improvement in oscillator output signal frequency stability

Communication apparatus for transmitting and receiving signals on different frequency bands

Abstract: A communication apparatus comprises a first oscillator for generating a frequency fp 1 at each channel step; a second oscillator for generating a modulated frequency fp 2 ; a first mixer for creating a transmission frequency which is a sum fp 1 +fp 2 of the frequencies of the first and second oscillators and a difference fp 1 -fp 2 therebetween on high and low band transmissions respectively; a third oscillator for generating a frequency fp 3 which is higher or lower than the frequency fp 2 of the second oscillator by a given frequency Δf; and a second mixer for creating a sum fp 1 +fp 3 of the frequencies of the first and third oscillators means and a difference fp 1 -fp 3 therebetween on low and high band transmissions respectively.

Metal oxide semiconductor logarithmic voltage controlled oscillator

Abstract: Voltage controlled oscillator (50) provides an exponential transfer function. The frequency of the output signal of the voltage controlled oscillator varies exponentially with the input voltages (VIN1, VIN2) to the oscillator. The exponential transfer characteristic is provided by means of a MOS field effect transistor (19) biased in its subthreshold range.

Phase locked loop with high and/or low frequency limit detectors for preventing false lock on harmonics

Abstract: A phase locked loop circuit (16) includes means to eliminate harmonic frequency locking. The phase locked loop includes a voltage controlled oscillator (1) which provides an output signal (V out ) which is compared with the input signal (V in ) by a phase detector (4). The output signal from the phase detector is integrated and the output signal of the integrator (7) is placed on the control input lead of the voltage controlled oscillator. The output signal of the voltage controlled oscillator is provided to a frequency detector (14, 17) which determines if the output frequency is within a predefined range. If the output frequency is above the predetermined range, a limiter circuit (15) provides a low voltage output signal to the control input lead of the VCO in order to pull the input voltage of the VCO to a voltage which corresponds with the appropriate operating range of the phase locked loop. If the output frequency of voltage controlled oscillator is below the predefined frequency range, the limiter circuit provides a high voltage output signal to the control input lead of the VCO in order to pull the input voltage of the voltage controlled oscillator to a voltage which corresponds with the proper operating frequency range of the phase locked loop.

Remote transmitter control system

Abstract: A remote transmitter system including a control station and a remote trantter station. The control station includes a variable frequency oscillator, a modulator, a parallel to series digital data converter and a DC power supply. The remote transmitter station comprises a power storage circuit, a phase-locked-loop demodulator, a local oscillator, a modulator and a power amplifier. The variable frequency oscillator provides two signals f o and f 1 that are harmonics of each other and are in-phase. These signals modulate the 0's and 1's of digital data that is transmitted along a coaxial cable to the phase-locked-loop demodulator that provides a control signal to the local oscillator and the modulated digital data signal (f o , f 1 ) to the modulator. The local oscillator generates two signals f A and f B , that have a predetermined phase and/or frequency relationship to f o and f 1 . The f o and f 1 signals are detected and applied to the modulator as a control signal (D o , D 1 ) that generates a serial input signal (f A , f B ) to the power amplifier and represents the binary data. The invention may be used with either phase modulation, or frequency modulation depending upon the design of the local oscillator. The two outputs f A and f B of the modulator can be designed to have any relationship of frequency for frequency modulation or phase for phase modulation.

Automatic frequency control system or an SSB receiver

Abstract: A frequency control circuit for a single sideband receiver is disclosed wherein the local oscillator is swept at a first rate to enable the acquisition of a transmitted signal. When the signal is acquired, the local oscillator is swept at a second rate in an indicated direction in order to center the signal. Upon centering, the local oscillator is maintained at a frequency which centers the signal in response to the activation of a squelch detector.

Drift-equalized, multi-frequency oscillator

Abstract: An oscillator having the ability to oscillate at a plurality of discrete frequencies in response to an applied digital signal is disclosed. A crystal-controlled, resonant circuit utilizing passive components as frequency determining elements and a PIN diode switching scheme allows the oscillator to demonstrate a tendency for each of the plurality of discrete frequencies to drift equally in response to temperature changes. A two-transistor, emitter coupled amplifying section uses a current mirror for biasing and provides an impedance matching network.

Phase locked loop frequency and phase modulators

Abstract: A signal generator is arranged to produce frequency or phase modulation at frequencies which extend from a high value down to zero, i.e. to a d.c. level shift. The output oscillator forms part of a phase locked loop which also includes a variable frequency divider. A modulation signal is applied to the loop, so that high frequency modulation signals directly modify the control signal which determines the frequency of the oscillator, and so that low frequency modulation signals alter the divisor value of the variable frequency divider so as to modify the frequency characteristics of the phase locked loop. Quantization noise is reduced by applying a masking signal to an analogue-to-digital converter which utilizes the low frequency modulation signals to alter the divisor value.

Receiver circuit comprising two phase control loops

Abstract: An FM receiver for demodulating an RF carrier signal containing a pilot frequency signal is provided. The receiver includes first and second frequency control loops. The first frequency control loop selects the local oscillator signal frequency. The reference signal oscillator in the first frequency control loop forms a part of a second frequency control loop. The second frequency control loop locks the phase of the reference signal oscillator with a detected pilot signal. In this way, the tuning signal of the local oscillator is kept phase locked to the detected pilot signal. Additional provisions are provided for changing the divisor of the second phase lock loop such that the time for establishing phase lock is reduced.

Method for temperature compensation of the digital signal output of a circuit arrangement comprising a position encoder

Abstract: A method is proposed which is used for temperature compensation of the digital signal output of a circuit arrangement for measuring a distance of travel by means of an inductive position encoder The circuit arrangement comprises an oscillator (10), the frequency of which changes as a function of the position of the position encoder (18), and an evaluating circuit (11) which converts the oscillator frequency into a digital distance signal To correct for the temperature-dependent oscillator frequency, a limit value for the distance of travel, which is still within the frequency range determined by the distance of travel, is stored in a ROM (25) The limit value is first transferred into a RAM (26) and cyclically compared with the oscillator frequency When the limit value is exceeded, the oscillator frequency is transferred as new limit value in the RAM (26) and the cyclically determined oscillator frequency is referred to the new limit value and converted into a correspondingly corrected distance signal (Figure 1)

Station selecting method for television receiver

Abstract: A method for tuning a television receiver in which an optimum local oscillator frequency is selected for offset stations. A local oscillator frequency of the receiver is incremented in steps of a first predetermined frequency interval beginning with a frequency at the bottom of an offset band around the center frequency of the local oscillator. As the local oscillator frequency is scanned, when both an up signal, indicative that the tuning frequency is above a predetermined range around the actual frequency of the received signal, and a down signal, indicative that the tuning frequency is below the predetermined range around the center frequency, the local oscillator is decremented by the first frequency interval and then incremented in a second, smaller frequency interval until the up and down signals are both lost. The local oscillator frequency is then increased and decreased by the first predetermined frequency interval, wherein, if both the up and down signals toggle states, the frequency at which both the up and down signals were lost when scanning with the second frequency interval is accepted as the best tuning frequency.

Offset cancelling AC level detector using an oscillator

Abstract: An alternating current small-signal detector is disclosed in which an oscillator output frequency jumps from a first frequency of oscillation to a second frequency of oscillation in response to the alternating current signal exceeding a predetermined value. The predetermined value is maintained over changes in input offset voltages by a feedback network which changes only the oscillator duty cycle.

Driving circuit for radio frequency dryer

Abstract: A driving circuit for supplying a radio frequency electrical signal to the applicator section of a radio frequency dryer (12) includes a voltage controlled oscillator (14), supplying a signal to an amplifier circuit (20). The amplifier circuit supplies an amplified signal to the applicator section of the dryer (12) via an impedance match circuit (42). The signal supplied to the applicator section is compared in phase with the output of the voltage controlled oscillator (14) and phase deviations are utilized to produce a signal which controls the frequency of the voltage controlled oscillator output, such that the applicator section of the dryer (12) is driven at its resonant frequency.

Performance Improvement of a Binary Quantized All-Digital Phased-Locked Loop with a New Aided-Acquisition Technique

Abstract: A nonuniform sampling digital phase-locked loop (DPLL) is proposed with a sequential loop filter, in which two additional phase comparators are added conjointly with an estimation-decision circuit controlling the two distinct modes, acquisition and tracking, in which the loop is to work. These additions provide more freedom to deal with the conflicting requirements of minimum acquisition time and maximum noise rejection in the presence or absence of frequency drift. Using a pseudo-two-dimensional random-walk filter, the stationary phase-error variance and the mean acquisition time have been evaluated by means of a numerical analysis. The comparison between the theoretical analysis and the experiments has proven to be very satisfactory. Substantial reduction of the acquisition time, without severely degrading the noise reduction performance, has been achieved. The improved ability of this modified loop to track frequency drift was also demonstrated. A digital loop "quasi-bandwidth" measure was used in the evaluation of the loop performance, thus allowing for a comparison with other digital loops and to a limited extent with a first-order analog loop. The usual difference in performance favoring the analog loop for high signal-to-noise ratio is shown to be substantially reduced and can be lowered by an appropriate choice of parameters.

Study of a UHF Mobile Radio Receiver Using a Voltage-Controlled SAW Local Oscillator

Abstract: Abswuct-Voice-grade signal-noise-distortion (SINAD) tests have been made on a 422 MHz mobile radio receiver incorporating a SAW delay-line local oscillator controlled by a digital phase-locked loop. Details are given of in-channel tests showing required 12 dB SINAD performance with -109 dBm RF input into the antenna, as well as adjacent channel selectivity tests yielding required 70 dB SINAD selectivity at 25 kHz frequency spacing. General details of the receiver circuitry are also given, including the SAW local oscillator with steppedfinger delay line operating in the fifth-harmonic mode. Stability performance tests made with an automated frequency stability analyzer and Hadamard variance techniques, yielded a phase noise < -1 15 dBc/ Hz at 10 kHz Fourier frequency offset, in accordance with expectations. Frequency drift in the IF stage of the stability analyzer was typically in the order of 0.15 Hz over the measurement sequence.

Digital and Analog Frequency - Temperature Compensation of Dielectric Resonator Oscillators

Abstract: The advent of the varactor tuned, dielectric resonator oscillator (DRO) has made possible both digital and analog frequency - temperature compensation (1). Seth techniques provide the DRO with a stability approximating that of a crystal referenced oscillator (i.e., better than +-50 ppm over -55° to +85° C) without the higher power consumption and spurious output signals.

Method and apparatus for eliminating harmonic skip

Abstract: A method is provided to eliminate harmonic skip problems in a down-conversion system. The method makes use of the relationship between the frequency of the intermediate frequency signal and the harmonic number of the local oscillator signal with respect to the frequency of the frequency of the source signal. By monitoring and measuring corresponding changes in the intermediate frequency signal caused by predetermined changes in the frequency of the local oscillator signal, a determination of the proper local oscillator signal and the proper harmonic can be made using a processor. The proper frequency and harmonic can then be maintained by periodically checking the relationship between variables.

PSK modulation by temporarily increasing frequency to achieve phase change

Abstract: A phase modulation low power integrated circuit communications arrangement which employs a frequency shift oscillator is disclosed. The frequency shift oscillator operates normally at a first frequency and is keyed to a second frequency for brief intervals to introduce cumulative first frequency phase change in an output signal. Subquadrature and larger increments of phase shift, spurious frequency component rejection with wave filters, and low power amplification of the modulated signal are also disclosed. Specifically, transitions in either (or both) of a pair of binary input signals cause a 45-degree (or 90-degree) phase shift in the phase-modulated carrier, unlike standard DQPSK modulation.

Frequency modulated transmitter applicable to MF broadcasting

Abstract: OF THE DISCLOSURE The invention concerns a frequency modulation broadcasting trans-mitter in which the output oscillator at the transmission frequency is modulated not directly by the audiofrequency signal but through the intermediary of a phase locking loop comprising a phase comparator supplied, on the one hand, by the output signal filtered from a picture or image frequency rejection mixer. This mixer receives, on the one hand, a modulated intermediary frequency signal from a modulator and, on the other hand, the output signal of the oscillator at the transmitting frequency Fs, the reference frequency Fo1 being determined as a function of the central transmitting frequency and of the intermediary frequency Fo1 = FS - F1 .

Arrangement for the stabilisation of the frequency produced by a frequency generator, in particular by a quartz generator

Abstract: 1. Arrangement for the stabilization of the frequency emitted by a frequency generator (VCO), in particular by a quartz generator, having a thermostat arrangement which keeps the frequency-determining elements of this frequency generator at a predetermined temperature, which thermostat arrangement consists of a thermostat housing which receives the frequency-determining elements and of a temperature controller which controls the internal temperature of this thermostat housing, which temperature controller has a heating element (HT) and a temperature sensor constructed as temperature-dependant frequency-change oscillator (TCO), the frequency of which temperature sensor is used for providing a control variable to be fed to the heating element, the frequency-determining elements of the frequency-change oscillator being likewise received in the thermostat housing and the temperature dependency of the frequency generator (VCO) and of the frequency-change oscillator (TCO) being, at least within a predetermined temperature range, varied to such an extent that, at the desired frequency of the frequency generator, a stable operating point of the first control circuit consisting of the frequency generator (VCO), the frequency-change oscillator (TCO) and the heating element (HT) arises, characterized in that the frequency-change oscillator (TCO) is included in a first phase-locked loop (PH2, R2, TCO, FT2), by means of which the frequency of the frequency-change oscillator can be controlled in the course of a calibration procedure by feeding a corresponding tuning variable according to a reference frequency to the stable operating point of the first control circuit.

Temperature-compensated frequency generator

Abstract: Temperature-compensated frequency generator of the type having a driving oscillator with piezoelectric resonator. The compensation is achieved with a piezoelectric resonator oscillator (2) used as a heat sensor. The sensing oscillator should be chosen to be an oscillator whose temperature drift is monotonic and much greater than that of the driving isolator within the operating temperature range. The generator comprises a frequency meter (4) for measuring the frequency of the sensing oscillator and a memory (6) whose output controls the means (7, 8) for regulating the driving oscillator (1) as a function of the result of the measurement. Application to cases requiring high temperature-dependent stability.

Harmonic components of decametric solar radio bursts

Abstract: Type-IIIb, IIId, and III solar decametric radio bursts, being distinguished by the typical negative drift rate of their dynamic spectra, are compared. Observational data were obtained with a UTR-2 antenna during the period 1973–1982. During the analysis of the bursts of all these spectral varieties, the frequency drift time (drift delay) was measured in the ranges 25 to 12.5 MHz, 25 to 20 MHz, and 12.5 to 10 MHz. Durations of type-III bursts were determined at the harmonically-related frequencies of 25 and 12.5 MHz; radio source locations were also used.