Showing papers on "Frequency drift published in 1982"

Temperature compensation of an oscillator by fractional cycle synthesis

Abstract: A method for temperature compensating the output of an oscillator circuit and apparatus for performing the method. This method employs fractional cycle synthesis to maintain the output frequency of a voltage-controlled oscillator at a desired value, the reference frequency of the circuit being derived from a crystal oscillator. To calibrate the circuit, the crystal oscillator is cycled in temperature. The frequency output of the crystal oscillator is accurately counted while a digital signal representing temperature is generated by an analog-to-digital converter from a temperature sensor. A signal representing the relationship between crystal frequency and temperature is stored in a memory and is available during actual operation of the oscillator for temperature compensation. During oscillator operation the output of the memory, as it relates to an instantaneous ambient temperature of the crystal, is appropriately treated and then injected into a phase locked loop containing the voltage-controlled oscillator, thereby affecting the input voltage to the oscillator to control the frequency output thereof. The stabilized frequency output of the VCO is offset from the crystal reference frequency and it is this offset that is shifted by very small amounts to provide the desired compensation of the oscillator output.

Wideband modulation sensitivity compensated voltage controlled oscillator

Abstract: A control oscillator voltage, the modulation sensitivity compensation broadband compensates automatically and continuously over a wide bandwidth modulation sensitivity changes resulting from changes in the center frequency of the oscillations. The oscillator comprises an array direction (30) coupled to the input of a network oscillator (20) for controlling the central frequency. A modulation network (50) is also coupled to the network input oscillator (20) via a compensation network (40). The compensation network (40) continuously varies the coupling between the modulation network (50) and the network oscillator (20) in response to control signals applied to the input (32) of the steering network (30) so as to compensate the variations in modulation sensitivity.

Method and apparatus for controlling AC motor

Abstract: A method and apparatus for controlling an induction motor, in which an AC power source is connected to the induction motor through a switch and a frequency converter, and the motor speed is controlled by controlling the output frequency and output voltage of the frequency converter. In the starting operation, the induction motor in a free-running state is supplied with an initial voltage in a given frequency which is expected to make the absolute value of the motor current minimum or near minimum, and then the supply voltage is increased gradually from the initial voltage with its frequency being retained at the given voltage. When the output frequency of the frequency converter reaches a predetermined value, the output frequency and voltage thereof are increased gradually with the ratio therebetween being maintained at a given value.

Horizontal scanning frequency multiplying circuit

Abstract: A horizontal scanning frequency multiplying circuit comprises a flip-flop supplied with a horizontal synchronizing signal having a horizontal scanning frequency f H , which is set by this horizontal synchronizing signal, a phase-locked-loop, and a counter. The phase-locked-loop comprises a voltage controlled oscillator for producing a signal having a frequency Nf H (N is an integer over 1) which is N times the horizontal scanning frequency f H , a frequency divider for frequency-dividing an output signal frequency of the voltage controlled oscillator, and a phase comparator supplied with one output signal of the flip-flop and an output signal of the frequency divider, for comparing phases of these signals and applying an output error signal to the voltage controlled oscillator to control the oscillation frequency of the voltage controlled oscillator. The counter is supplied with the other output signal of said flip-flop which is reset by this output signal, and supplied with the output signal of the voltage controlled oscillator within the phase-locked-loop as a clock signal, and produces a counted output every time the clock signal is counted for a predetermined counting time T, to supply this counted output to the flip-flop in order to reset the flip-flop. The voltage controlled oscillator within the phase-locked-loop produces a signal having a frequency Nf H .

Spectral characteristics of solar S bursts

Abstract: Observations of the solar radio spectrum have been made with high time and frequency resolution. Spectra were recorded over six 3-MHz bands between 30 and 82 MHz. The receivers used were capable of time and frequency resolutions of 1 ms and 2 kHz, respectively. A large number of radio bursts exhibiting a variety of find spectral structure were recorded. The bursts, referred to here as S bursts, were observed throughout the 30–82 MHz frequency range but were most numerous in the 33–44 MHz band and were very rare at 80 MHz. On a dynamic spectrum the bursts appeared as narrow sloping lines with the centre frequency of each burst decreasing with time. The rate of frequency drift was about 1/3 that of type III bursts. Most bursts were observed over only a limited frequency range (< 5 MHz) but some drifted for more than 10 MHz. The durations measured at a single frequency and the instantaneous bandwidths of S bursts were small; Δt = 49 ± 34 ms and Δf = 123 ± 56 kHz for bursts observed near 40 MHz. A significant number had Δt ≤ 20 ms. Flux densities of S burst sources were estimated to fall in the range 1023-5 × 1021 Wm−1 Hz−1. A small proportion (1–2%) of bursts showed a fine structure in which the burst source apparently only emitted at discrete, regularly spaced frequencies causing the spectrogram to exhibit a series of bands or fringes. The fringe spacing increased with wave frequency and was δf ∼- 90 kHz for fringes near 40 MHz. The bandwidths of fringes was narrow, often less than 30 kHz and in some cases down to 10–15 kHz.

Variable frequency U. H. F. local oscillator for a television receiver

Abstract: A tunable oscillator develops a signal having a frequency variable over a range of frequencies in response to a control signal. A frequency determining resonant circuit includes two voltage-variable capacitance diodes in an arrangement for adjusting at least one endpoint of the frequency range. As a result, the relationship between the magnitude of the control signal and the frequency of the oscillator signal can be adjusted while avoiding mechanically adjustable reactive elements. The disclosed arrangement is suitably employed with resonant circuits other than those in oscillators.

Voltage controlled crystal oscillator having wide frequency range

Abstract: To extend the variation range of a controlled frequency oscillator comprising a piezoelectric element, a lithium tantalate or lithium niobate element is used in parallel with which there is connected a linearization circuit comprising an inductance in series with a parallel circuit comprising a resistor and a capacitor.

Wideband phase locked loop tracking oscillator for radio altimeter

Abstract: A wideband phase locked loop oscillator (PLLO) for tracking the frequency of an altitude signal in an FM/CW type radio altimeter. The phase locked loop oscillator conventionally includes a voltage controlled oscillator (VCO), a phase comparator for comparing the phase of the altitude signal to be tracked with the phase of the VCO output and an error signal amplifier for applying the output of the phase comparator as control voltage to the VCO. The frequency range of the PLLO is extended by changing the natural frequency of the VCO in steps spanning the useful frequency range of the altitude signal. Selection of the proper value of VCO natural frequency is effected through microprocessor directed digital control.

A simple three-phase variable-fraquency oscillator

Abstract: The paper describes a hybrid, three-phase oscillator with variable frequency and voltage, and reversible phase sequence. The oscillator digitally generates three 120° phase shifted square waves, and mixes them in balanced modulators with a fixed frequency sine wave. The signals from the modulators are token through active filters resulting in constant amplitude, low distortion three-phase sine wave outputs. The magnitude of the output, voltage is controlled by varying the amplitude of the fixed frequency sine wave source. It has good frequency and phase stability.

Apparatus for controlling the receive and transmit frequency of a transceiver

Abstract: Apparatus for maintaining a transmit radio signal frequency in a predetermined frequency relationship with a received radio signal. A common voltage controlled frequency source serves as an Lo signal generator for both the receiver and transmitter. A reference frequency oscillator is phase compared with a receive IF signal to derive a control voltage for the voltage controlled frequency source. The resulting phase lock loop provides transmit signal frequency control with respect to a received signal.

Linear sweep frequency modulator for FM/CW radio altimeter

Abstract: A linear sweep frequency modulator for a varactor tuned transistor microwave oscillator used in an FM/CW radio altimeter where the oscillator-frequency v. varactor bias characteristic is non-linear. A linear triangular wave is converted by means of a function generator to the non-linear wave required for varactor bias to cause linear frequency modulation of the oscillator. Linearity of modulation is tested by measuring variations in the period of a calibration signal derived from a delay line. Variations in the period of the calibration signal are measured by determining the difference between the average and the instantaneous calibration period and sampling the difference during each cycle of the triangular wave, once during the upswing thereof when the oscillator is at low frequency and once during the down swing thereof when the oscillator is at high frequency and separately integrating the up swing and down swing samples. By applying both results of integration to the function generator it thereby has its biases controlling the low frequency and the high frequency operation of the oscillator separately adjusted.

Simplified frequency scheme for coherent transponders

Abstract: A coherent transponder having a transmitter and a receiver operating at different frequencies with each including a numerically controlled oscillator for controlling the frequency thereof through a single-sideband modulator and various outputs from a phase-locked loop the frequencies of the numerically controlled oscillators and the phase-locked loop being referenced to a single crystal controlled oscillator.

Apparatus for improving the frequency stability of a transmitter oscillator circuit

Abstract: A novel apparatus and method for improving the stability of an electrical circuit such as an oscillator and/or a radio frequency transmitter which is coupled to a radiating element wherein the radiating element such as a loop is coupled to the inductor or capacitor of the frequency determining circuit of the oscillator so that frequency shifts will not occur due to inductive or capacitive effects. The oscillator circuit is mounted on an insulating sheet which has a ground plane on the opposite side thereof so as to provide effective shielding and the radiating element is mounted on a portion of the insulating sheet where the grounding plane does not extend. The radiating element is also coupled symmetrically to the inductor or capacitors of the frequency determining circuit and is connected at tap points which do not have the entire inductance between them.

Voltage controlled oscillator having approximately constant modulation sensitivity

Abstract: A voltage controlled oscillator for use in a phase locked loop is provided with a first varactor circuit that responds to a control signal to set the center frequency of the oscillator, and with a second varactor circuit comprising a modulation varactor that responds to a modulation signal to cause the oscillator to produce a modulated output. The modulation sensitivity of the oscillator is made relatively constant between upper and lower center frequencies by applying a portion of the modulation signal to the first varactor circuit in addition to the control signal.

Oscillator having manual and automatic frequency control

Abstract: A variable frequency oscillator 10 has an output frequency Fo responsive to a voltage input Vo derived from an analogue integrator 11 controlled by potentiometer 15, 16, the frequency Fo being displayed on frequency meter 19 having a ghost least significant digit. A converter 24 responds to the digit of a digital output fed to a digital to analogue converter 20 providing an error voltage Ve whose magnitude is proportional to the deviation of the digit from a datum, e.g. 5, and whose polarity depends on whether the deviation is + or -. The voltage Ve is also fed to the integrator 11 to control the voltage Vo. An arrangement is also described in which the voltage Ve is derived from the divider chain of a gate period generator controlling a frequency counter whose input is Fo.

Wide band frequency phase locked loop frequency synthesizer

Abstract: The synthesizer comprises a single phase loop formed by two stages of a frequency divider inserted between the voltage controlled oscillator and the phase comparator. The synthesized frequency is taken from the connection between the two stages, which allows a frequency range to be obtained extending over a wide band with a voltage controlled oscillator itself having a small relative band width.

Voltage controlled oscillator using a voltage tunable filter with feedback

Abstract: A voltage controlled oscillator for producing an output signal having a frequency proportional to the magnitude of an input control signal includes a tunable filter circuit for simulating a resistance-inductance-capacitance (RLC) circuit with a resonant frequency approximately equal to the base or center frequency around which the voltage controlled oscillator is to operate. Through appropriate feedback means and multiple gain paths within the simulated RLC circuit, there is provided an output signal whose frequency is a function of the input control signal.

Frequency modulation transmitter

Abstract: A frequency modulation transmitter has a frequency synthesizer (8) comprised of a voltage controlled oscillator (1) for operating a transmitter section (33) of the modulation transmitter. The output center frequency of the voltage controlled oscillator (1) is determined by channel designation information. The level of a modulation input signal (11) applied to the voltage controlled oscillator (1) for modulating the center frequency is changed in accordance with the channel designation information.

Quasi-optical balanced biconical mixer

Abstract: A biconical antenna, the halves of which are connected together at the apex by a pair anti-parallel diodes through a pair of parallel conductive whiskers or wires. A pair of quasi-optical lenses focuses energy from a local oscillator and from a submillimeter radio source, respectively, onto the diode pair in the end-fire and broadside direction, respectively. The diode pair spacing is equal to the half wavelength of the local oscillator energy. The local oscillator energy is common mode rejected and causes the incoming radio energy to be sampled by forward biasing the anti-parallel diode pair in synchronism with each zero crossing of the local oscillator energy. Accordingly, the local oscillator energy and noise virtually do not affect the current flow between the halves of the biconical antenna. The current flow represents an intermediate frequency signal corresponding to the difference in frequency between the incoming radio signal frequency and the local oscillator frequency. Thus, local oscillator energy is mixed with incoming radio energy without permitting local oscillator noise to degrade the resulting mixed signal.

Rapid starting variable frequency oscillator with minimum startup perturbations

Abstract: An LC-type oscillator employing a differential amplifier to switch a tank circuit in response to a feedback signal. A voltage controlled variable capacitor is employed to control the frequency of oscillation. The bias across the variable capacitor is closely controlled to avoid errors in the frequency of oscillation during the period of startup, which would otherwise create an undesired error in the oscillation frequency.

Stable monolithic GaAs FET oscillator

Abstract: A monolithic X-band GaAs FET oscillator has been developed. Passive circuit components are lumped capacitors and inductors on semi-insulating GaAs; the chip size is 1.2 × 1.4 mm2. Stabilised with a Ba2Ti9O20 dielectric resonator, the oscillator delivers more than 30 mW output power at 10.8 GHz with a maximum chip efficiency of 20%. The frequency drift is better than 1 × 10¯6/K from -20°C to 80°C.

Experimental and theoretical study of drift-waves in a quadrupole. II. Radial eigenfunctions

Abstract: Drift waves in a plasma with a density gradient are expected to behave like standing waves in the direction parallel to the density gradient, confined to a region around the point of maximum gradient and evanescent outside this region. Because of finite Larmor radius effects the higher radial harmonics are predicted to have lower frequencies. The authors show that in the quadrupole, confinement at the inner boundary is probably due to a layer of rapid velocity shear and with this assumption the observed radial eigenfunctions are in reasonable agreement with those predicted; the lower frequency drift wave observed in earlier work is identified as the first radial harmonic. There is a significant departure from the theory, however, in that the drift wave is observed to become a radially propagating wave in the outer regions of the plasma. The energy outflow associated with this propagation is evaluated and shown to be small compared with the input rate due to the drift wave instability mechanism.

Temperature Stabilization of GaAs FET Oscillators using Dielectric Resonators

Abstract: A model of frequency drift with temperature of GaAs FET oscillators, stabilized using dielectric resonators is presented. Conditions for output power, oscillation frequency and frequency stability have been derived. A stacked resonator with linear resonance frequency-temperature characteristic has been developed using Barium Titanate and Titanium Zirconate dielectric material. It enabled the realization of a highly stable oscillator at 11.5 GHz with total drift of ±120 KHz in the temperature range of ?20°C to 80°C.

Television receiver phase locked loop tuning arrangement

Abstract: In a channel selection system of a television receiver set using a frequency synthesizer system, the local oscillator output of a voltage controlled oscillator in a tuner is coupled to through a prescaler to a programmable frequency divider. To a frequency division ratio specification input terminal of the programmable frequency divider is coupled a frequency division ratio setting data from a frequency division ratio memory. When the broadcast wave frequency is deviated from a predetermined value due to the frequency division ratio setting data, a fine tuning data corresponding to the deviation and a direction specification data representing the direction of the deviation are memorized in a random-access memory (RAM). The fine tuning data read out from the RAM is coupled to a fine tuning signal generator where it is added to or subtracted from the frequency division ratio setting data prevailing in the programmable frequency divider. The data obtained from the fine tuning signal generator as a result of the addition or subtraction is coupled as a new frequency division ratio setting data to a frequency division ratio specification input terminal of the programmable frequency divider.

Phase-locked loop with reduced frequency modulation

Abstract: A phase-locked loop provides an output frequency, locked to a multiple N of a reference frequency, responsive to a frequency-control voltage supplied to the output-frequency-generating voltage-controlled oscillator from the output of a differential amplifier. The differential amplifier inputs are provided with voltages sampled from the output of a pair of integrators respectively enabled for integration during complementary, and substantially identical, portions of the phase detector output waveform. Output-frequency-control voltage ripple is substantially reduced, with concomitant reduction of frequency modulation of the output freqeuncy, over the reference frequency period.

A digital system for measurement of resonant frequency and Q factor

Abstract: A new automatic computer-controlled system for accurate measurement of the resonant frequency and Q factor of radio frequency and microwave resonant circuits was developed and tested. In this system, the inflection points of the resonance curve are identified through a process of mathematical evaluation using an on-line digital computer and utilized to calculate the resonant frequency and the Q factor. The primary advantage of the system is that the results are independent of the resonant circuit characteristics at the resonant frequency and the 3-dB points, amplitude and frequency drift of the signal source, as well as detector instabilities. An experimental system operating between 1 and 2 GHz was designed, assembled, and tested with a laboratory minicomputer PDP 11/34 used for data acquisition and processing, as well as for overall system control. The measured range of Q factors is 100–1500, with estimated uncertainties of 40 ppm in the resonant frequency and 7 percent in the Q factor for a resonant circuit with a Q factor of 1000.

Oscillator control circuit

Abstract: An oscillator is controlled so that it produces the correct frequency in the transmitting condition, and so that it produces a slightly different frequency in the receiving condition. This is achieved by a circuit which supplies a first control voltage to the oscillator for transmitting and which supplies a second and different control voltage to the oscillator for receiving. This second and different control voltage causes the oscillator frequency in the receiving condition to be different so that there is no interference to or improper operation of a repeater system. The circuit also prevents any modulation signals from reaching the oscillator in the receiving condition, thus preventing false signals or other problems.

A Digitally Compensated Hybrid Crystal Oscillator

Abstract: A thin film hybrid temperature compensated crystal oscillator has been developed which utilizes digital compensation techniques to maintain a stable output frequency with respect to changes in temperature. The digitally compensated crystal oscillator (DCXO) described has been designed to be compatible with automated manufacturing. techniques in large volume production, a problem with conventional compensated oscillator designs. A look-up table, where each temperature increment corresponds to a particular compensation value, is maintained in an electrically erasable read only memory (EEPROM). This memory, together with an on-board I/O port, allows programing and reprogramming after the oscillator has been sealed. Thus, software can compensate for any subsequent changes in the frequency of the oscillator. Also, the I/O port and EEPROM memory permit automation of the programming and testing for multiple units simultaneously.

Transmitter receiver operating at 94 ghz

Abstract: A solid state transmitter/receiver operating at 94 GHz is shown to comprise an injection-locked pulsed oscillator for transmitting interrogating pulses and a first local oscillator for heterodyning with received signals to produce an intermediate frequency (I.F.) signal, both such oscillators being phase-locked to a master oscillator operating at a frequency below 94 GHz.