Showing papers on "LC circuit published in 1976"

Control system for driving a capacitive display unit such as an EL display panel

Abstract: A coil is serially connected to a capacitive display unit, such as an EL display panel, which includes an insulating display element sandwiched between a pair of electrodes. The coil and the electrostatic capacitance of the display unit function, in combination, to form an LC resonance circuit, which limits transient current flowing through the insulating display element and enables the display unit to operate in a low power dissipation mode. An alternating driving signal to be applied to the display unit has an intermediate potential period on which a writing pulse is superimposed, thereby to minimize high voltage requirement of the writing circuit.

Discharge lamp auxiliary circuit with dI/dt switching control

Abstract: A variable frequency AC source drives a gas discharge lamp which is connected in parallel with the capacitance of a series resonant circuit. The polarity of the voltage applied to the resonant circuit is commutated at such times as the rate-of-change of current flow in the resonant circuit is at or near zero. The source frequency is thus maintained at or near the circuit resonant frequency to maintain high output voltage when the lamp is starting or reigniting. The polarity is also commutated at such times as the current flow from the source reaches a predetermined level. Lamp current is thus controlled in the running mode.

Uhf tuning circuit utilizing a varactor diode

Abstract: In the UHF tuning portion of a television receiver, a varactor tuned circuit is coupled to the gate electrode of a field effect transistor (FET) through an impedance transformation network comprising a series connected capacitor and shunt connected inductor. In order to increase the signal power transferred between the tuned circuit and the FET at the lower end of the UHF range, the values of the capacitor and inductor are selected so that the relatively low value of equivalent parallel impedance exhibited by the tuned circuit at the lower end of the UHF range is impedance transformed to a value approximately equal to the value of the impedance exhibited at the gate of the FET. A second impedance transformation network, similar to the first, is coupled between the drain of the FET and a second varactor tuned circuit to further increase the signal power transferred between the FET and the second tuned circuit at the lower end of the UHF band. The values of the capacitor and inductor comprising the impedance transformation networks are also selected so that the signal power gain of the UHF tuning portion at the upper end of the UHF range is not substantially degraded. Because of the impedance transformation networks, resonant points below the lowest frequency in the UHF band are established.

Discharge lamp operating circuit

Abstract: Circuit operating from a direct current source applies DC pulses to a high pressure sodium vapor lamp to improve the color properties of the lamp. The circuit includes a controlled thyristor switch in series with the lamp, an RC timing circuit for periodically turning on the switch at predetermined intervals, and an LC circuit for turning the switch off. An inductor comprising the primary winding of a transformer in series with a diode across the capacitor of the LC circuit provides for discharge of the capacitor to enable subsequent re-charging thereof, so as to produce the desired pulsed operation of the circuit, and the transformer secondary winding in series with a diode clamps the voltage of the primary winding. The disclosed arrangement prevents excessive voltage across the controlled switch and provides for the control of lamp wattage with respect to changes in lamp voltage.

Radio-frequency tuned-circuit microdisplacement transducer

Abstract: An inductance-capacitance loop defines a resonant circuit and is arranged in a member subject to stress. Strains resulting from the stress vary the inductance or capacitance of the circuit, and its resonant frequency. A dip meter is used to detect the resonant frequency and thus provides a reading indicative of the stress in the member.

Method and apparatus for remotely transducing and transmitting pressure and temperature changes

Abstract: A capacitance-type transducer capsule is placed in a remote environment forxposure to its changing physical conditions. A energy pick-up coil in the capsule receives a remotely-generated signal which is converted to DC power for chargeably establishing the capacitance and for driving a tank circuit which includes the capacitance as the only variable. Changes in pressure, temperature, etc. produce linear variations in the capacitance to modulate the oscillations of the tank circuit and produce a transmittable signal frequency containing the sensed information.

Resonant switching power conversion

Abstract: A description is given of the operating cycle of the resonant switching dc-to-dc power converter. A method is outlined for precise voltage regulation against line and load changes. Sufficient analysis is presented to form the basis for preliminary design to meet any set of input and output requirements. Performance features are outlined for a flight qualified, highly efficient, light weight resonant switching converter for the U. S. Navy's Navigation Technology Satellite (NTS-2).

Dynamic stabilization of tuned-circuit levitators

Abstract: Recent investigations of a relatively new magnetic levitation device are described. This device uses an electromagnet, which is the inductive part of a resonant circuit. If the circuit is properly tuned, static stability is attainable. Levitators built on these lines are simple and reliable. However, it is already well known that a tuned circuit electromagnet on its own is usually not sufficient to maintain levitation for long periods of time, and the suspended object tends to be dynamically unstable. This dynamic instability is prevented by introducing simple electronic or mechanical modifications into the tuned circuit system. Such modifications are described and their investigation is dealt with. The electronic method of stabilization is successfully analyzed by employing the viewpoint of slowly varying quantities. It is believed that the present article is the first to suggest mechanical methods for introducing dynamic stabilization to levitators. It is interesting that mechanical stabilization is achieved without a necessity of employing direct mechanical contact, and the levitated object is suspended freely. The system is stabilized by electromechanically coupling an aluminium solid object to the main levitator circuit.

Oscillation means for generating a differential AC signal proportional to movement of a conducting member

Abstract: A high frequency pickoff is disclosed having two spaced inductors electrically connected in series and a capacitor connected in parallel with the inductors, thereby forming a parallel resonant circuit. A conducting member is mounted for motion in the space between the two inductors. A pair of transistors are mounted in push/pull configuration to alternately connect first one end and then the other of the resonant circuit to a source of electrical energy. The source disclosed is a current source for matching the high impedance of the parallel resonant circuit. When the electrical energy is switched at substantially the resonant frequency of the parallel circuit, differential motion of the conducting member relative to the inductors provides differential amplitude output at the frequency of resonance of electrically opposed ends of the resonant circuit. A configuration for enhancing gain in the pickoff circuit includes tuning capacitors connected parallel with each of the inductors and providing similar resonant frequencies therewith slightly removed from the overall circuit resonant frequency. Pickoff circuit gain is enhanced by an increase in the differential output due to changes occurring in each inductance as well as changes occurring in the frequency of maximum impedance associated with each tuned inductive capacitive leg of the circuit.

Implantable receiver circuit

Abstract: In an implantable receiver circuit there is provided a tuned filter responsive to externally provided radio frequency energy bursts. The receiver also includes a pair of oppositely poled diodes for respectively providing positive and negative rectified versions of the energy bursts. The cathode of one diode is coupled through a low-pass filter circuit to an output capacitor and the anode of the other diode is coupled through a low-pass filter to the control electrode of a semiconductor switching device, the main electrodes of which are coupled between the output capacitor and the point of reference potential. With this connection the switching device is rendered conductive during the time no energy burst signals are applied to the tuned circuit thereby allowing the output capacitor to discharge during this time. During the time an energy burst is provided, the second rectifier circuit maintains the switching device non-conductive.

Double-balanced frequency converter

Abstract: A frequency converter of the type having a local oscillating stage for producing a local oscillating signal and a double-balanced type mixing stage provided with a first pair of inputs for receiving a signal to be frequency converted and a second pair of inputs for receiving the local oscillating signal. The output of the mixing stage can be connected through a tuned circuit so as to frequency convert the input signal to an intermediate frequency (IF) signal. The local oscillating stage includes a first pair of differentially-connected transistors, the collector electrode of one being connected to a resonant circuit and, additionally, through an RC positive feedback circuit to the base electrode of the other transistor. The double-balanced type mixing stage includes a second pair of differentially-connected transistors, one of which being connected in cascade with a first differential amplifier and the other of which being connected in cascade with a second differential amplifier. The base electrodes of the second pair of differentially-connected transistors receive the local oscillating signal which is applied thereto in opposite phase relation. The first and second differential amplifiers both receive the input signal which is applied thereto in opposite phase relation. A DC bias circuit is provided for applying substantially equal bias voltages through equal impedances, such as resistors, to both pairs of differentially-connected transistors. Preferably, the DC bias circuit includes an emitter-follower.

Moisture measuring apparatus

Abstract: A moisture measuring apparatus includes a tuned circuit, a moisture sensor, coaxial cable means between the sensor and the tuned circuit wherein the tuned circuit tunes the coaxial cable, and a circuit for ascertaining the loading presented by the sensor to the tuned circuit whereby moisture is measured. The sensor is alternately connected and disconnected to an end of the coaxial cable and the signal drive across the tuned circuit is standardized, when the sensor is disconnected, for zeroing the instrument. Also, the gain of the circuitry is adjusted by periodically providing a standard load to the tuned circuit while adjusting amplification to bring about a standard output. The apparatus is not as sensitive to cable changes as prior apparatus and a plurality of selectable coaxial cables are provided on reels adjacent the sensor console.

Resonant sensor using a phase locked loop detector

Abstract: A speed sensor circuit for providing a speed signal representative of the speed of a vehicle comprises a resonant tank circuit whose resonant frequency is modulated in accordance with the speed of the vehicle and a phase locked loop detector circuit which locks onto the frequency of the resonant tank circuit and provides a demodulated output signal representative of the vehicle speed.

Vehicle tire pressure supervisory system

Abstract: The wheels at opposite ends of an axle - and which may be twin or tandem wheels -- each have a pressure switch and a tank circuit associated therewith, rotating with the wheel. The tank circuits includes a normally closed pressure-sensitive switch which, when the pressure in the respective tire drops below a certain value, opens the tank circuit. The coil of the tank circuit is coupled with a transducer coil connected to a blocking oscillator which, upon passage of the tank circuit, provides an output pulse. The frequency or recurrence rate of the output pulses from opposite ends of the wheels at an axle are compared in an integrating comparator and, if the frequencies differ after a predetermined integration time, provide an alarm signal. The integrator or a digital counter which should have a number of count stages, only the last one providing an alarm signal to allow for variation in frequency with normal tire pressure when the vehicle rounds a curve. Tandem or multiple wheels at one end of the axle each can be provided with a tank circuit, offset 90° with respect to each other, however. Use of tandem wheels increases the absolute frequency and does not change the comparison system.

Differential transistor pair integrated circuit oscillator with L-C tank circuit

Abstract: A differential transistor pair has an antiresonant tank connected between collectors. Feedback is achieved using a pair of cross connected zener diodes biased into reverse breakdown. A balanced two-pin version provides paraphase output and an unbalanced single-pin version is available for single phase output. The single pin version can include a current mirror for biasing the zener diodes with constant current. The oscillator can be temperature compensated by means of a temperature programmed current source.

Telemetric measuring apparatus for biological objects

Abstract: Signals from a high frequency transmitter outside of the biological object are received in a resonant receiving circuit inside the object whose resonant frequency corresponds to the value of the parameter being measured. The signal from the resonant receiving circuit is applied to the input of a frequency multiplier whose output is connected to a second resonant circuit tuned to the multiplied frequency. The second resonant circuit transmits a return signal to a receiver outside of the biological object which is also tuned to the higher frequency. The signal at the receiver will have a maximum amplitude when the transmitter frequency is equal to the frequency of the first resonant circuit as tuned by the value of the parameter. The adjustment of the transmitter frequency required for receiving maximum energy at the receiver is a measure of the value of the parameter in a first embodiment. An alternate embodiment, the frequency of the transmitter is wobbled by means of a sawtooth voltage generator, the time difference between the sawtooth flyback and the maximum amplitude of the signal at the receiver constituting a measure of the value of the parameter.

Microwave diode coaxial circuit oscillator improvement

Abstract: An improvement in a prior art microwave diode coaxial oscillator circuit comprising an unloaded fundamental frequency cavity for prevention of energy loss in the matching termination at the resonant frequency of the circuit and a second harmonic resonant cavity for controlling second harmonic loading of the diode and for reducing noise in the output signal.

Multiple-load induction heating cooking apparatus with means for eliminating interference between two or more commutation circuits

Abstract: A multiple-load induction heating cooking apparatus comprises two or more induction heating commutation circuits each having the junction between its commutating inductor and capacitor manually selectively connected by corresponding one of a plurality of interconnecting switches equal in number to the commutation circuits to form a series-connected LC circuit to a high frequency energy source. The potential at the common point of connection is compared with a reference potential to produce an error signal which is used to control the frequency of the energy source so that the potential at the common point is maintained constant regardless of the magnitude of induction heating loads.

Direct reading inductance meter

Abstract: A direct reading inductance meter is comprised of a crystal oscillator for generating a reference frequency f r and an LC tuned oscillator for generating an initial frequency f o which, when mixed with the reference, produces a difference equal to zero. Upon connecting an inductor of small unknown value in the LC circuit to change its resonant frequency to f x , a difference frequency (f r -f x ) is produced that is very nearly a linear function of the inductance of the inductor. The difference frequency is measured and displayed on a linear scale in units of inductance.

Circuit element - has at least one inductor in the shape of a flat coil located on an organic film carrier

Abstract: The parent application relates to an electrical L or LC network with balanced condensers having at least one inductor and shunt capacitor consisting of layers over an organic film carrier and separated by a coating of a dielectric, and which can be balanced by removing a portion of layer using a laser beam. In this addn. the inductor is in the shape of a flat coil applied to the organic film carrier. Pref. the inductors and capacitors are applied over a series of organic film carriers lying one over the other, and the terminals are contacted with each other and with connecting wires.

A stable low-level oscillator with cryogenic applications

Abstract: Some general factors affecting the stability of low-level oscillators are considered and a design is given for an active circuit to drive a low Q tank circuit with a dissipation below 10-9 W. The circuit is insensitive to supply voltage variations, and contributes less than 1 part per million per degree, to the drift in frequency with temperature. The results of tests of its performance driving a magnetic thermometer used below 1K are described.

Estimation of mechanical transients in ''tuned-circuit'' levitators by employing steady-state impedances

Abstract: Investigations of a relatively new magnetic levitation device are described. This device uses an electromagnet, which is the inductive part of a resonant circuit. If the circuit is properly tuned, static stability is attainable. ’’Tuned‐circuit’’ levitators are characterized by typical transients of the suspended object which are difficult to analyze. The work described here is a contribution towards simplifying the calculations of such transients. The analysis presented in the paper relies on calculating the impedance of the tuned circuit for each position of the suspended object. Though the impedance obtained in this way is merely the ’’steady‐state’’ impedance of the circuit, it enables one to predict some of the parameters characterizing the mechanical transients of the suspended object. The frequency of mechanical oscillations is the main parameter to be predicted in this way. Investigations were conducted where the predicted mechanical frequency of oscillations was compared with that obtained experimentally. The results of the experiments were usually close to those expected by theory.

Synchronous pulse generator including flywheel tank circuit with phase locked loop

Abstract: A circuit receiving a degraded synchronous pulse signal which has missing pulses and phase-shifted pulses, and producing an output signal similar to and at a constant phase angle with the input signal, in which the missing pulses have been replaced and the phase-shifted pulses shifted to the correct relative position. Provision is made for adjusting output signal frequency to long term drift in input signal frequency.

Voltage variable capacitor tuned radio receiver having delayed automatic frequency control at turn-on

Abstract: A voltage variable capacitor tuned radio receiver having a circuit which delays operation of a portion of the radio receiver circuit which includes the automatic frequency control circuit after the radio receiver is first energized until the filter capacitor at the output of the tuning voltage generator has charged to a selected tuning voltage to prevent the automatic frequency control circuit from locking the radio receiver onto an undesired RF carrier frequency.

Dual channel wide-band frequency modulated keyable control circuit and keying circuit therefor

Abstract: A dead-oscillator detector in a wide band frequency modulated keyable control circuit averts attempted actuation of the unlocking function by the coupling of untuned energy-absorbing material, such as iron, to a sensing coil. The energy absorbing material, being unresponsive to frequency, reduces the rf energy in the sensing coil approximately uniformly at all swept frequencies. The dead oscillator detector, lacking an ac component in the rf envelope over the entire frequency band, generates an inhibit signal which prevents the unlocking function. When a tuned circuit is properly coupled to the sensing coil, the resulting ac component in the rf envelope provides one required enable signal to unlock circuits.

Circuit for the production of an open alternating magnetic field

Abstract: In an induction energy transfer device comprising a static power conversion circuit for producing an alternating magnetic field of ultrasonic frequency of the type wherein the static power conversion circuit includes a parallel resonant circuit which comprises a coil which also couples power across an air gap, an improvement in efficiency and power transfer is obtained by including at least two such parallel resonant circuits in the power conversion circuit, one of which resonant circuits is tuned to the third harmonic of said fundamental frequency.

Dual frequency narrow-band frequency modulated keyable control circuit and keying circuit therefor

Abstract: A keyable control circuit generates a narrow-band FM signal A keying circuit, containing two tuned circuits, placed next to the tank coil of the keyable control circuit, absorbs rf energy each time the FM signal sweeps past the resonant frequency of one of the tuned circuits Detector circuits within the keyable control circuit, upon sensing the amplitude modulation imposed by the cyclic absorption by one of the tuned circuits, cause the rf frequency of the FM signal to jump to a second frequency region If the second tuned circuit in the keying circuit matches the new frequency, detector circuits again detect the amplitude modulation imposed by the cyclic absorption After detecting the second signal, the keyable control circuit generates an electrical control signal output for use by external circuits

Constant delay resonant tank circuit combination for frequency discrimination

Abstract: The method of designing a circuit having a substantially constant delay over a given frequency band and having a substantially linear attenuation characteristic or amplitude change characteristic over the same frequency band and the product resulting from such a design approach. One such approach uses a primary tank circuit having a given Q and amplitude response feeding two secondary tank circuits each of which have a higher Q and amplitude response and wherein the resonant points are on either side of the resonant point of the primary tank. By adjusting the Q, amplitude response and resonant frequency of the three tanks, the "delayless" and linear amplitude change characteristics over a given frequency band can be achieved.

R.f. amplifier circuit

Abstract: An R.F. amplifier circuit having a high selectivity with a simple and inexpensive construction is provided. An R.F. choke coil acting as a bias supplying element is connected to a collector of an amplifying transistor to supply it with an optimum biasing current for a high electric field strength. A first capacitor is connected in parallel, at a high frequency, with the R.F. choke coil, which is connected to an LC tuning circuit through a second capacitor. A resonance frequency of the R.F. choke coil and the first capacitor is chosen to be sufficiently lower than that of the LC tuning circuit to maintain a single tuned circuit while at the same time an output impedance of the amplifying transistor is stepped up by the first and second capacitors to insure a high quality factor.

Precise determination of equivalent circuit parameters of quartz crystal resonators

Abstract: A new technique is developed for the precise determination of the equivalent circuit parmeters of a quartz crystal resonator: the series resonance frequency, the series resistance, the series inductance, and the capacitance ratio This technique is unique in that the parameters are determined from the measured data of the crystal admittance by means of computer processing