Showing papers on "Frequency drift published in 1978"

High frequency voltage generator

Abstract: This high frequency voltage generator which may be used particularly in surgery for supplying an electric bistoury, comprises a power oscillator operating an output transformer. A chopping supply is placed in the direct control chain of the power oscillator. The output voltage of the generator is controlled by a first regulation loop whose reference value is increased by means of a positive feedback proportional to the output current.

Multi-mode relaxation oscillator

Abstract: In a relaxation oscillator where the oscillation frequency is proportional to the charge rate of a capacitor, independent current sources are connected through separate switches to change the charge rate of the capacitor and thus the oscillation frequency. Each switch is controlled by signals from a separate detector of a condition which requires that the oscillation frequency be changed. An oscillation frequency increase between the standby and alarm modes of a smoke detector is accomplished in one disclosed embodiment and duty cycle means for controlling the operative period of the alarm indicator during each cycle of the increased oscillator frequency is disclosed in a more particular embodiment.

Double vernier time interval measurement using triggered phase-locked oscillators

Abstract: Measurement of a time interval between a start and a stop event is made by activating a start oscillator in response to the start event and activating a stop oscillator in response to the stop event. The number of cycles of each respective oscillator signal which occur between the activation of each oscillator and the coincidence of the respective oscillator signal with that of an independent time base is determined. The number of cycles of the time base signal between the coincident points of it and the start and stop oscillator signal is also determined. These numbers, which are always integers, are used along with the values for the time base period and the difference in frequency between the time base oscillator and the start and stop oscillators to calculate the time interval. Resolution of the measurement is dependent on the frequency difference between the time base signal and the start and stop oscillator signals. Two triggered-phase oscillators, which are phase-locked to the reference oscillator, are used to supply the start and stop frequencies. The start trigger and stop signals are used for phase shifting, i.e., restarting of the oscillators rather than starting the oscillators. This allows for pre-trigger frequency control, and essentially eliminates post trigger frequency drift which usually occurs when an oscillator is first started. The coincidence signals are provided by the phase cross-over between the phase locked oscillator and the reference by a digital mixer.

Phase corrected raster scanned light modulator and a variable frequency oscillator for effecting phase correction

Abstract: The present invention relates to a phase corrected raster scanned light modulator in which information modulated on a carrier is used to form a grating whose spatial frequency along the scanning line varies in accordance with the signal modulation frequency. Thickness variation in the medium on which the grating is formed causes an undesired phase modulation of the light which may be corrected by altering the carrier frequency. A novel oscillator is described which may be stepped discontinuously in frequency while the waveform and its slope remain continuous, which is of sufficient accuracy and agility to provide a real time region by region phase correction of the raster in the light modulator. The variable frequency oscillator is of high stability and can step from one value to another for intervals as short as one microsecond.

Phase-locked loop with variable gain and bandwidth

Abstract: A phase locked loop includes a voltage-controlled oscillator, and a phase and frequency detector for comprising an input signal pulse wave with a pulse wave from the voltage-controlled oscillator, and for providing a frequency control voltage to the voltage-controlled oscillator. When the pulses overlap, a pulse comparison circuit in the phase and frequency detector produces a frequency "up" signal or a frequency "down" signal proportional to the correction necessary. When the pulses do not overlap, the pulse comparison circuit produces a "non-overlap" signal which effects a rapid frequency correction by causing a current pump in the phase and frequency detector to increase its output to a fixed maximum value, and by causing a loop filter to increase its bandwidth to a fixed maximum value.

Thickness-shear mode quartz oscillator with an added non-circular mass

Abstract: A thickness-shear mode quartz oscillator characterized in that an addition mass fitted to a driving electrode of the oscillator for the purpose of adjusting its oscillation frequency has a non-circular shape or the fitting position thereof is deviated from the center of a quartz slice, or both in combination. Such addition mass provides different piezoelectric effects and effects of addition of the mass between the fundamental main vibration and harmonic vibrations and eliminates or restricts a "frequency abnormal phenomenon". Consequently, even when driven by a C-MOS type integrated circuit not having a frequency selection circuit in its oscillation loop, the thickness-shear mode quartz oscillator exhibits stable frequency-temperature characteristics.

Frequency bandwidth tuning system and method

Abstract: An electronic system for scanning across a range of received signals and aining a digital representation of a predetermined position, for example, the mid-point, of the bandwidth of the received signal, without having to ascertain directly the frequency at said predetermined position The system can include a homodyne receiver (zero-beat reception) using a voltage controlled local oscillator or a superheterodyne receiving using a local oscillator for producing an intermediate frequency

Superheterodyne receiver of scanning type with indicator means to display received frequency and frequency being stored in memory

Abstract: A superheterodyne receiver of a scanning type, comprising a high frequency amplifier, a mixer, a local oscillator, an interdmediate frequency amplifier, a detector, an audio frequency amplifier, a loud speaker, and an automatic scanning/manual scanning selecting switch, said local oscillator comprising a digital frequency synthesizer comprising a voltage controlled oscillator, a programmable frequency divider for dividing the frequency of the output from the voltage controlled oscillator, a reference oscillator, a random access memory for storing the information concerning the rate of the frequency division by the frequency divider, and a phase detector for phase detecting the frequencies of the outputs from the reference oscillator and the frequency divider for providing a control voltage to said voltage controlled oscillator, said receiver further comprising an astable multivibrator for generating pulses for scanning the frequencies of the receiving bands, a counter for counting the pulses from the astable multivibrator, a decoder for decoding the count output from the counter, a plurality of light emitting diodes correspondingly coupled to the decoder output, a plurality of switching transistors connected to a plurality of bit parallel outputs of the random access memory, a plurality of switches for presetting in the random access memory the information concerning the rate of frequency division by the frequency divider corresponding to a predetermined channel, a squelch circuit responsive to a noise detected output obtained when the said detector detects a noise for disabling the audio frequency amplifier, a plurality of undesired channel setteing switches for presetting a channel reception of which is not desired, and a switching transistor responsive to the reception of the frequency corresponding to the channel as set by the said undesired channel setting switch for providing a potential for forcibly enabling the said squelch circuit for disabling the audio frequency amplifier.

Coherent frequency shift key demodulator

Abstract: Disclosed is a frequency shift key demodulator for the coherent detection of both mark and space tones. Cross coupled phase locked loops lock onto and track the difference in frequency between translated mark and space tones. An additional set of cross coupled phase locked loops locks onto and tracks overall frequency drift of the mark and space tones. Signals are generated within the first set of cross coupled loops allowing for coherent detection thereby permitting detection during signal to noise ratios of less than one. Loop bandwidths can be independently controlled and are independent of the data rate thus permitting wide system flexibility.

Non-linear control circuit

Abstract: A low-Q mechanical resonator is operated in its series resonance mode in a circuit that includes an amplifier and voltage variable phase shifter. As the phase shift is varied, the resonator will shift its frequency to compensate the phase shift. The result is a voltage variable oscillator frequency. The low-Q resonator has a non-linear phase versus frequency characteristic so that frequency is not a linear function of control voltage. A plural emitter transistor is employed in one side of a non-linear differential control amplifier. The resulting non-linear transfer characteristic is used to compensate the non-linear oscillator characteristic so that the frequency versus control voltage is linear.

Phase locked loop with switchable filter

Abstract: Disclosed is a phase-locked loop which comprises a voltage controlled variable frequency oscillator (1), a phase comparator (2) having a cosine characteristic and receiving a reference oscillation as well as that supplied by the oscillator (1), and a low-pass filter (3) connected between the output of the phase comparator (2) and a frequency control input of the oscillator (1). The transfer function of the low-pass filter (3) is switchable between two characteristics depending on the instantaneous phase difference between the reference oscillation and that supplied by the oscillator. The first low-pass filter transfer function is adapted to the phase-locked operation of the loop, while the second transfer function is adapted for frequency capture.

Frequency stabilization technique for microstrip oscillators

Abstract: An apparatus for frequency stabilizing a microstrip oscillator using an integrated diplexer as a frequency discriminator. The crossover frequency of the microstrip diplexer is used in a feedback arrangement to stabilize a millimeter-wave oscillator. The diplexer is coupled to the output of the oscillator and detects a shift from the desired oscillator output frequency. This shift in frequency is converted to a voltage for controlling the varactor tuning element of the oscillator to thereby return the oscillator to the desired operating frequency. Means are also provided for sensing a temperature change in the diplexer and for insuring that the oscillator output frequency is maintained at the desired frequency regardless of this temperature change.

Radio receiving and retransmitting apparatus with frequency lock circuit

Abstract: In radar apparatus for actively enhancing and retransmitting a received radar signal, the incoming signal is mixed with the output of a first local oscillator, the resulting signal being supplied to a frequency lock loop which varies the frequency of the first local oscillator until the frequency of the resulting IF signal is equal to a first reference IF frequency. The first local oscillator output is mixed with the output of a second local oscillator, the frequency of which is varied until the frequency of the resulting second IF signal is equal to a second reference IF frequency. The output from the second local oscillator is retransmitted. The first and second reference IF frequencies are identical if the frequency to be retransmitted is the same as the incoming RF carrier frequency.

Control of ultrasonic vibratory transducer - has phase comparator maintaining oscillator frequency equal to resonance frequency

Abstract: The transducer has a resonant circuit, and is controlled by a voltage or current controlled oscillator (3). A voltage is derived corresponding to the phase of the current supplied to the transducer. This voltage is applied to a phase comparator (1) as a first input signal, whose second input signal is the transducer driving voltage. The voltage or current controlled oscillator is controlled by the phase comparator output signal in accordance with the phase difference between its two input signals. This results in the transducer driver frequency being always equal to the resonance frequency.

Communication tuning system utilizing local oscillator frequency selection for maximum RF filter bandwidth and method thereof

Abstract: The local oscillator frequency in a communication tuning system is selected to either high side mix or low side mix as appropriate to place the local oscillator frequency and image frequency outside the bandpass range of the bandpass filter. This allows bandpass filters having a frequency range equal to approximately twice the IF frequency in a transmitter, and approximately four times the IF frequency in a receiver.

Digital pressure sensor

Abstract: A first oscillator is associated with a pressure detector so that frequency of an output signal of the first oscillator varies in response to variations of the detected pressure. A second oscillator having a same construction as the first oscillator is provided for determining a sampling period of the output signal of the first oscillator, thereby compensating for variations of the frequency of the output signal derived from the first oscillator due to variations of temperature, humidity, a power supply voltage, etc.

Selectively tunable heterodyne receiver

Abstract: A selectively tunable heterodyne receiver including a plurality of frequency conversion stages which can be tuned to a desired receiving frequency by the use of two voltages which control the coarse and fine tuning adjustments and wherein the first voltage is supplied to a first injection oscillator to control the harmonic output of a crystal controlled harmonic generator and wherein the second voltage is supplied to a second injection oscillator which is continuously variable within a frequency range corresponding to the frequency spacing between the adjacent harmonics of the harmonic generator and wherein the second oscillator is stabilized to the desired adjusted frequency

Angle Modulation Limits of a Noise-Free Phase Lock Loop

Abstract: Methods are presented for determining the modulation limits of phase lock loop (PLL) FM demodulators These limits establish the maximum deviation that the PLL can support (ie, remain "inlock") based on the loop design parameters The modulation limits are derived from experimental data on first and second order loops using sinusoidal and Gaussian noise modulation The analysis of each PLL is broken into two regions, low frequency and high frequency modulation It is shown that the deviation limit remains constant with modulation frequency for a first order loop in the low frequency region In the high frequency region the deviation limit increases with increasing modulation frequency for both first and second order loops The deviation limit in a second order loop increases with decreasing modulation frequency in the low frequency region and is a function of the loop damping

Optical frequency shifting for Rayleigh scattering spectroscopy (laser velocimeters)

Abstract: The Doppler frequency shifting of reflected light is achieved by a moving mirror. By adopting an optical control system for driving the mirror, tunable frequency shifts over a range from 500 Hz to 30 kHz have been obtained and the long-term drift for a given frequency offset has been sufficiently stabilised. As a typical result, it is found that the frequency drift over one week is +or-3 Hz at a frequency shift of 3.16 kHz, and the spectral broadening is 1.0+or-0.2 Hz.

Radar receiver local oscillator control circuit

Abstract: An improved automatic frequency control arrangement for a missile-borne inverse receiver is shown to include a reference oscillator and a voltage-controlled oscillator with control means for the latter, such means including a frequency-to-voltage converter responsive to the difference frequency between the two oscillators so that the latter may produce a signal representative of the Doppler shift frequency of a target A starting circuit is also shown to ensure that the frequency of the reference oscillator is always lower than the frequency of the voltage-controlled oscillator

Local oscillator circuit having two phase locked loops having respective frequency dividers with a common division ratio

Abstract: A first phase locked loop produces a local oscillator signal. The output of a second phase locked loop is connected to the input of the first phase locked loop. A first variable frequency divider is connected in the first phase locked loop. A second variable frequency divider having the same frequency division ratio as the first frequency divider is connected between a variable frequency oscillator and the input of the second phase locked loop. An adder adds a base frequency of preferably 1 MHz to the output frequency of the second frequency divider. With the frequency of the variable frequency oscillator set at a center frequency, the frequency of the local oscillator signal is equal to the frequency division ratio of the frequency dividers multiplied by 1 MHz. Any variation in the frequency of the variable frequency oscillator from the center frequency is algebraically added to the local oscillator frequency, regardless of the frequency division ratio, as an offset frequency. The frequency range of the variable frequency oscillator is low compared to the frequency range of the local oscillator signal, thereby enabling low frequency drift. A gate disables the first phase locked loop when the second phase locked loop is not in lock.

Signal transmitting system

Abstract: A capacitive signal dependent upon a quantity being measured is produced by capacitive sensors of a radiosonde. An oscillator in the radiosonde has an output frequency, controlled by the capacitive signal, in the order of 1 to 10 MHz. The output frequency of the oscillator is divided by a factor of 27. A high frequency transmitter in the radiosonde is frequency modulated by a frequency fM1 =fM0 /d wherein fM1 is the output frequency of the divider and fM0 is the input frequency of the divider.

High-Q multi-mode resonator controlled source

Abstract: An oscillation control circuit in which the output of an unstabilized oscillator is controlled using a bulk acoustic wave resonator. The circuit includes a high and low frequency loop with the power output of the oscillator being divided and supplied along respective paths to the high and low frequency portions of the loop. The high frequency portion of the loop, which includes the BAW resonator, operates at the output frequency f0, which is equal to the sum of the oscillator frequency f1 and the frequency f2 of the low frequency portion of the loop. A first mixer receives the frequencies f0 and f1 and produces an output f2 in the low frequency portion of the loop, while a second mixer receives the frequencies f1 and f2 and produces an output f0 in the high frequency portion of the loop. In this way, as the oscillator output frequency f1 varies, the frequency f2 in the low portion of the frequency loop varies inversely, so that the up-down conversion performed by the system maintains f0 constant.

An Rf Linear Modulation Circuit

Abstract: This paper describes a linear FM modulation circuit. The modulation circuit and oscillator, which are in microstrip, exhibit exceptional slope linearity and group delay with no external frequency compensation over a deviation bandwidth of 2% of the RF frequency. The baseband frequency response of the modulator/oscillator is greater than dc to 150 MHz. This modulation circuit has been used with microstrip oscillators at 1.8 and 5 GHz.

Temperature compensated integratable RC oscillator

Abstract: A high stability integratable resistance-capacitance oscillator is disclosed which is capable of operating at a stable frequency regardless of changes in ambient temperature or applied voltages. The oscillator uses a temperature compensating impedance and semiconductor junction to compensate for temperature dependent variations in active elements of the oscillator. Constant current bias sources and voltage clamping circuits insure oscillations having predetermined amplitude ranges despite changes in applied voltages. Active transistors in the oscillator are maintained in their linear range by the use of antisaturation transistors connected between their base and collector electrodes.

Stabilization of a Complex Resonator He–Ne Laser

Abstract: A complex resonator He–Ne laser at 633 nm was constructed as a local oscillator for measuring the absolute wavelength of a Co2 laser. It is stabilized by a dual servo-control system. One is a frequency offset-lock system, by which the frequency of the laser is stabilized so as to hold an offset frequency from an iodine stabilized He–Ne laser as a master laser. The other is a sub-resonator control system, by which the output power of the laser is stabilized. The laser oscillates at a single frequency with a maximum output power of 10 mW. The oscillation frequency can be turned over a 1.5 GHz spectral range and locked without modulation to any frequency over a range of ±15 MHz of the offset frequency from the master laser. A frequency stability of ±1×10-11 and an output power stability of ±4×10-4 are obtained.

Frequency measuring device for telecommunication systems

Abstract: A device capable of being operated under the control of a programmer for rapidly measuring the differences between the actual values of a plurality of transmitted signal frequencies and their assigned values. It comprises a constant frequency local oscillator, a modulator fed from said oscillator and from a signal the actual frequency of which is to be determined, a bandpass filter fed from the output of said modulator, another local oscillator producing a constant frequency, and means for measuring the frequency difference between said other oscillator and the output frequency of the filter. Arrangements are provided for displaying the measured frequency difference values in digital form.

Linear crystal controlled FM source for mobile radio application

Abstract: A narrow deviation voltage controlled crystal oscillator (VCXO) circuit has been developed that exhibits near-linear tuning characteristic and, unlike previously reported circuitry, is extremely simple and straightforward in design and highly economical with regard to material and fabrication costs. The design principle makes use of a linear reactance modulator incorporating abrupt junction varactor diode developed by M. Driscoll, and previously reported by Driscoll and Healey in connection with the design of a wide deviation VCXO for radar application. Because the total oscillator turning requirements are only on the order of 1 part in 105, however, much of the circuit complexity has been eliminated, and the problem of interdependence between linearity and center frequency adjustment has been solved. Network equivalence theorems have been utilized to reduce the total number of required circuit inductances to only one, and the composite resonator has been reconfigured to operate on the series resonance of its impedance characteristic allowing simple means for prevention of oscillation at spurious network resonances through the addition of a single resistor. Laboratory measurement of transmitter FM distortion using a number of FM oscillator modules reveals repeatable achievement of less than 0.5 percent distortion with linearity adjustment and less than 1½ percent without any adjustment. Also, the achievement of repeatable linear tuning characteristic has simplified the oscillator modules so that required temperature stability is obtained by addition of negative temperature coefficient (NTC) capacitors to the oscillator circuit and a single simple three-point thermistor compensation circuit that is easily designed and provides simultaneous temperature dependent compensating voltage for all radio oscillator modules. The oscillator design also allows for direct parallel connection of multiple modules (for multichannel operation) having commonly connected tuning input and signal output ports.