Showing papers on "LC circuit published in 1993"

Automatic antenna tuning method and circuit

Abstract: A method of matching the resonant frequency of an antenna resonant circuit (18, 46) to the output frequency of a transmitter output stage (26), the method includes the step of providing a powering signal from the transmitter output stage (26) to the antenna resonant circuit (18, 46). The method further includes the step of receiving at the antenna resonant circuit (18, 46) the powering signal, the antenna resonant circuit (18, 46) comprising a tuning circuit (48). The tuning circuit (48) is operable to variably modify the resonant frequency of the resonant circuit (18, 46). At its output the antenna resonant circuit (18, 46) provides a phase correlation signal having a known relationship to the frequency difference between the resonant frequency and the powering signal. A phase comparator (60) then receives the powering signal and the phase correlation signal and correspondingly adjusts the resonant frequency of the resonant circuit (18, 46) based upon the known phase relationship. Other devices, systems and methods are also disclosed.

Power converter having optimal dynamic operation

Abstract: A DC to DC, fixed frequency, Buck family power converter having a first feedback control loop for regulating output current or output voltage depending on the operational mode selected, a second feedback control loop for current mode control and a third feedback control loop for providing improved dynamic response for all conditions of line and load. The third feedback control loop senses the output voltage and generates a variable ramp signal having a slope (M) which is proportional to the converter output voltage. By maintaining as a constant (K) a ratio of the variable ramp slope (M) to the falling slope (M 2 ) of a voltage representation of the inductor current in an LC network of the Buck regulator or K=M/M 2 , improved dynamic operation of the power converter results for a plurality of output voltages particularly improving output ripple rejection and minimizing effects of injected noise in the current mode control loop.

An active square loop frequency selective surface

Abstract: An active frequency selective surface incorporating PIN diodes as switches is discussed. Waveguide simulation studies show that the frequency response of the surface can be electronically switched from that of a reflecting structure to a transmitting structure. A semi-empirical model based on a series-connected LC equivalent circuit approach gives agreement with measurements. >

High frequency ceramic multi-layer substrate

Abstract: A high frequency ceramic multi-layer substrate includes a stripline (1) embedded between two dielectric layers (2,2') having ground electrodes (3,4) at the top surface and at the bottom surface thereof and an electric circuit formed on another dielectric layer (5) applied to one of the ground electrodes. The stripline is connected to the electric circuit through via holes (6,6') provided through the dielectric layers. The equivalent length from the stripline to the electric circuit is a fourth of the wavelength of an input high frequency signal, to result in high frequency attenuation circuit. Another high frequency ceramic multi-layer substrate includes further another electrode provided via another dielectric layer of larger dielectric constant to form a capacitor with one of the ground electrodes, and a further dielectric layer for forming an electric circuit thereon is applied to the electrode. The stripline is connected to the electric circuit through via holes provided through dielectric layers. The electric circuit may be an impedance matching circuit of the stripline or a direct current bias circuit (8). This multi-layer structure makes the high frequency substrate compact and improves high frequency characteristics.

Series resonant converter having a resonant snubber

Abstract: A fixed frequency, series resonant converter having a resonant snubber comprising an inductor and capacitor connected across a tank circuit of the converter. An optimum amount of inductance in the resonant snubber minimizes the degree of "shoot-thru," or conduction through a body-diode within a transistor switch of the converter caused by ringing, which allows for nearly sinusoidal current to be provided to a full bridge high voltage rectifier enabling the power converter to operate at a higher frequency. An alternate embodiment applies the resonant snubber only across a selected transistor switch.

Vectorial signal combiner for generating an amplitude modulated carrier by adding two phase modulated constant envelope carriers

Abstract: A circuit for combining first and second signals having the same frequency. The signals have a relative phase shift, 2a(t). The circuit generates a signal that is proportional to the sum or difference of signals. The circuit appears to be a resistive load; however, the circuit can be constructed from purely reactive circuit elements, and hence, does not dissipate energy. In one embodiment, the circuit is constructed from a transformer and two LC circuits in which the capacitance is varied in response to a(t). The circuit may be used to construct a high efficiency RF amplification stage.

Proximity actuator and reader for an electronic access system

Abstract: An identification token and reader circuit for an electronic identification and latch/alarm system, the token comprising an LC resonant circuit, a digital counter, an analog or digital demultiplexer and at least one analog switch. The token's supply voltage is derived from the token's resonant LC circuit by a rectifier means when the token is proximal to a suitable oscillator as found in a reader/controller. The device is useful for access control in an electronic lock and key system. When the token is brought near to the lock part, an oscillator contained within the lock part oscillates at a high frequency. The oscillation is picked up by the key part where it is modulated with a frequency or pulse pattern serving as a key identifier, then transmitted back to the lock part where the enclosed carrier is demodulated by means of synchronous detection and processed by recognition means at the lock side.

Electronic circuit utilizing resonance technique to drive clock inputs of function circuitry for saving power

Abstract: An electronic circuit uses a resonance technique to reduce power consumption. The circuit contains function circuitry (14) that performs electronic functions. Certain elements (14F) of the function circuitry change state at a circuit frequency in response to one or more input signals, typically clock signals (CKR and CKR), that change state at the circuit frequency. A resonant system (50 or 140), which oscillates at the circuit frequency, is operated close to a resonant frequency so that the resonant system is largely in resonance. Oscillations of the resonance system typically include frequency components attributable to the fundamental resonance frequency and at least one other resonance frequency of the system. The resonant system is coupled to the function circuitry in order to help the indicated elements in changing state by overcoming parasitic capacitances and/or inductances associated with the function circuitry.

FM wireless transmission system with tank circuit tuning in wireless portable speakers

Abstract: A wireless local transmission system includes a separate transmitter and receiver. The transmitter converts an audio signal and/or an audio and video signal into a modulated signal within the 902-928 MHz frequency band and transmits the modulated signal to the receiver which reconverts the modulated signal to a frequency band below 900 MHz for use by a radio or television receiver.

Three-loop control for multimodule converter systems

Abstract: A three-loop control scheme for multimodule power converter systems with a secondary LC filter is presented. In addition to output voltage and inductor current feedback, the control scheme employs feedback from the output capacitor of each module to improve the dynamic performance of the system, particularly the transient response in the event of failure of a module. The superiority of the three-loop control over the conventional two-loop current mode control is demonstrated by both small-signal analysis and large-signal simulations. >

Isolated gate drive

Abstract: A drive circuit for use in UPS and like devices, designed to derive high-level switching signals from low-level logic signals. The drive circuit has an input circuit which drives the primary of an air-core transformer, the input drive circuit having an oscillator with a resonant circuit producing a carrier at a carrier frequency, the resonant circuit including the primary of the transformer and a coupling circuit for coupling the logic signals to the oscillator so as to modulate the carrier signal. The use of the resonant circuit enables generation of sufficient magnetization current for the low-cost transformer while reducing the current drive required of the input drive circuit, thereby enabling a reduced cost gate drive circuit.

Magneto-optical recording utilizing signal phase adjustment

Abstract: Magneto-optically recorded data can be recorded at high density, such that the data can be overwritten by a simple arrangement and with a small energy. Also, data of high recording density can be accurately recorded and reproduced by a simple arrangement. An alternating field having the same frequency as that of a recording fundamental clock generated by a PLL circuit (8) is generated by a coil (5) that is part of a tank circuit (7) and then applied to a magneto-optical disc (1). A phase of the recording fundamental clock is modulated by a phase modulating circuit (12) in association with recording data and a pulse synchronized with leading edge and trailing edge of such clock is generated by a pulse generating circuit (13). An optical pickup device (4) irradiates the magneto-optical disc (1) with a laser light in synchronism with the pulse. Therefore, a high density recording method in which the edge position of pit is shifted stepwise in association with data to be recorded can be applied to a magneto-optical recording medium.

Metal halide electronic ballast

Abstract: An electronic ballast can be connected between either a DC power supply or an AC power supply and a gas discharge lamp, such as a metal halide lamp and control the electrical power supplied thereto. An inverter receives a DC power and generates a periodic waveform at a controlled frequency. A resonant circuit is connected to the inverter and tuned to resonate at a predetermined frequency and generate an output voltage. A coupling capacitor is connected between the resonant circuit and the discharge lamp and supplies the output voltage of the resonant circuit thereto. A controller sets the frequency of operation of the inverter near the resonant frequency of the resonant circuit. The controller is responsive to at least a predetermined set point control voltage and to the output voltage of the resonant circuit. The resonant circuit is tuned to increase the voltage from the inverter means to a level sufficient to cause the discharge lamp to enter a glow mode of operation. The coupling capacitor and resonant circuit have an appropriate impedance to maintain sufficient power flow to the discharge lamp to carry it through the glow mode of operation, into an arc mode of operation and to a steady-state mode of operation.

Multi-output DC-DC converter using a resonance circuit

Abstract: A multi-output converter capable of stabilizing the output voltages Vo1, Vo2 and Vo3 of a first to a third output circuits, respectively, converted from the input voltage Vi of a DC voltage source. The output voltage Vo1 is stabilized by a frequency modulation technology using a switching device, a resonance circuit, an error detecting circuit, and a modulating circuit. The output Vo2 is stabilized by a pulse width modulation scheme using the switching device, error detecting device, and modulating circuit. Further, to stabilize the output voltage Vo3, a resonance frequency modulating circuit is applied to control the resonance frequency of a variable resonance circuit on the basis of the error voltage of an output voltage. The converter can accommodate even three or more outputs circuits with a minimum of loss and a miniature, reliable and inexpensive configuration.

Loop antenna with series resonant circuit and parallel reactance providing dual resonant frequencies

Abstract: A loop antenna (10) is provided with feed means (12,14) and a variable capacitor (C1) to adjust a first resonant frequency of the antenna (10). A reactive network (C2,L2,X) is included which permits the antenna to provide a further resonant frequency. The reactive network comprises a series-resonant circuit (L2,C2) in parallel with a further reactive element (X). The resonant frequency of the series-resonant circuit is arranged to be substantially equal to the first resonant frequency of the antenna as tuned by the capacitor (C1). The reactance (X) thus has no effect at this frequency. Another resonant frequency for the antenna may be adjusted by altering the reactance (X). The arrangement may be extended to provide further resonant frequencies.

Pi lc filter and pi lc filter array

Abstract: PURPOSE: To obtain a miniature π LC filter and an array thereof, having a high productivity and requiring a less mounting cost, that reduce the number of components in the installation in equipment, simplify routing of wires on circuit boards for downsizing of equipment, and are free from cracking and characteristic variation during the manufacture thereof CONSTITUTION: A π LC filter is formed as follows: A laminated chip capacitor 12 is integrated with a laminate chip inductor 11 through adhesive 13 of thermosetting resin or glass paste, with the top of the chip capacitor 12 mated with the bottom of the chip inductor 11 A first external electrode 21 is electrically connected with a third external electrode 33; a second external electrode 22 is electrically connected with a fourth external electrode 34 COPYRIGHT: (C)1994,JPO

Doubly broadband triple resonance or quad resonance NMR probe circuit

Abstract: A single NMR sample coil of inductance L S , in series with a mid-frequency (MF) tuning inductor grounded at one end, is doubly broadbanded using a first high-voltage broadband capacitor matching network in series with the two coils for the LF tuning and a second high-voltage broadband capacitor matching network connected to the junction between the two coils for the MF tuning. Isolation between the MF and LF ports is achieved by proper choice of a plug-in isolation capacitor between the two broadband matching networks. An inductively coupled floating HF tank circuit is inserted in series with one of the leads from the sample coil to produce the triple resonance circuit. The tuning elements for this HF tank are mounted on top of the adjacent broadband matching network. A second floating HF tank circuit may be inserted in series with the other lead from the sample coil to produce a balanced-HF triple resonance circuit or an unbalanced quad-resonance circuit. The tuning elements for the second HF tank circuit are mounted on top of the other broadband matching network. The inductors used in the HF tank or tanks each have inductance less than L S . The MF tuning inductor has inductance greater than L S /4 but less than 2L S .

Power supply circuit for a gas discharge lamp

Abstract: A power supply circuit for a gas discharge lamp is disclosed. The power supply circuit includes a circuit for providing a d.c. bus voltage on a bus conductor, and a resonant lamp circuit. The resonant lamp circuit includes a gas discharge lamp, a first resonant impedance in series with the gas discharge lamp, and a second resonant impedance substantially in parallel with the gas discharge lamp. The resonant load circuit operates at a resonant frequency determined by the values of the first and second resonant impedances. Further included is a series half-bridge converter for impressing across the resonant load circuit a bidirectional voltage, and thereby inducing a bidirectional current in the resonant load circuit. The converter comprises first and second switches that are serially connected between the bus conductor and a ground conductor, that have a common node coupled to a first end of the resonant load circuit and through which the bidirectional load current flows, and that have respective control terminals for controlling the conduction states of the switches. A circuit is provided for generating a feedback signal representing current in the second resonant impedance. Feedback circuitry, responsive to the feedback signal, provides respective control signals on the control terminals of the first and second switches. The feedback means controls the switching of the switches in such manner as to reduce a phase angle between the bidirectional voltage and the bidirectional current when the feedback signal increases, and vice-versa. Lamp power and lamp current are less subject to variation as the line voltage varies.

Electrically-and-magnetically-coupled, batteryless, portable, frequency divider

Abstract: A batteryless, portable, frequency divider includes a first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency; and a circuit element electrically connecting the first resonant circuit to the second resonant circuit. The first resonant circuit is coupled magnetically to the second resonant circuit to transfer energy to the second resonant circuit at the first frequency in response to receipt by the first resonant circuit of electromagnetic radiation at the first frequency; and at least one of the first resonant circuit, the second resonant circuit and the circuit element includes an active element, such as a variable reactance element or a semiconductor switching device having gain, for causing the second resonant circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first resonant circuit at the first frequency.

Double tuned circuit with balanced output and image trap

Abstract: Conversion of an RF signal amplifier from an unbalanced signal configuration to a balanced signal configuration is provided while including an image trap for both sides of the balanced circuit. The grounded side of the secondary of a double tuned circuit is lifted from ground to provide a balanced circuit configuration. A trap filter is provided in the balanced circuit configuration by a pair of small capacitors coupled between the balanced secondary leads to appropriate signal nodes.

Admittance-parameter estimator for a piezoelectric resonator in an oscillator circuit

Abstract: Equivalent circuit parameters of a piezoelectric resonator are measured in order to precisely control the amplitude and/or frequency of oscillation of an oscillator including the resonator, or to compensate for variations in the amplitude and/or frequency of oscillation. Significant variations are caused by shunt capacitance, and to a lesser degree, series resistance. The equivalent circuit parameters are measured by exciting the resonator at a plurality of frequencies, measuring responses of the resonator at the frequencies, including a complex response at one of the frequencies, and determining a value of the shunt capacitance from the responses. Preferably, the resonator is simultaneously and continuously excited at three different frequencies, one of which is approximately the resonant frequency of the resonator. The complex responses are measured by complex demodulation, and the circuit parameters are computed from the responses by solving simultaneous equations resulting by setting each complex response equal to the admittance of the equivalent circuit at each different frequency. In this fashion, the equivalent circuit parameters are measured periodically during continuous operation of the oscillator for correction or compensation of the amplitude and/or frequency of oscillation.

Radio frequency amplifier

Abstract: An amplifier for amplifying RF signals comprises a transistor, a first impedance, an impedance transformer, and a tuned resonant circuit. The amplifier receives the RF signals via a signal terminal of the transistor, wherein the RF signals are amplified by the transistor, the tuned circuit, the first impedance, and the impedance transformer. The degree of amplification is based on the impedance ratio between the impedance transformer and the first impedance, wherein the first impedance may be an output impedance matching transformer.

Resonant power factor correction circuits with resonant capacitor-voltage and inductor-current-programmed controls

Abstract: It is shown that, by using the control techniques proposed, one can use current driven resonant power converter topologies in designing resonant power factor correction circuits (RPFCCs). Based on the fact that the energy stored in the resonant tank circuit can be programmable, two types of control techniques that allow for fast output regulation are reported. These techniques are known as resonant tank capacitor-voltage-programmed control and inductor-current-programmed control. A design example based on the resonant capacitor-voltage-programmed control technique and computer simulations is given. >

Method and apparatus for reducing local oscillator leakage in integrated circuit receivers

Abstract: Technique for reducing local oscillator leakage in integrated frequency conversion circuits. The technique includes the step of coupling an external portion (35) of a resonator circuit (31, 35) to the integrated frequency conversion circuit (200). The coupling is accomplished without using any of the DC power or ground pins of the conversion circuit. A frequency conversion circuit based on this technique includes resonator, oscillator, and mixer circuits. Part of the oscillator and mixer circuit (16, 13) is encapsulated in a package (200), whereas at least a portion of the resonator circuit (35) is located outside the package. The outside portion of the resonator circuit (35) connects to at least two external resonator pins (43a, 43b) of the package (200) such that, during the operating of the conversion circuit, the net current entering the package via said external resonator pins (43a, 43b) is approximately zero.

Circuit arrangement for a tunable resonant circuit

Abstract: A circuit arrangement for a tunable resonant circuit is described which is of particularly simple construction and can be monolithically integrated. The arrangement can be used particularly advantageously in radio clock receivers for a number of different time signal transmitters.

Radio frequency measuring apparatus

Abstract: A device is provided for measuring dielectric constant and conductance of a material such as massecuite, the device including a pair of electrodes which are switchably connected to a tank circuit which includes a variable frequency oscillator operating at radio frequencies, and two reference frequencies are measured with the electrodes disconnected from the oscillator and two measurement frequencies with the electrodes coupled to the oscillator tank circuit, the differences between the reference and measurement frequencies being used to compute the inductance and dielectric constant or composition of the material. The frequency is modified by not more than about 10 MHz and may be achieved either by switchably introducing additional inductance or capacitance into the tank circuit to modify its frequency or by having the electrodes switchable between a pair or oscillators operating at known radio frequencies.

High-frequency induction heating inverter with multi-resonant mode using newly developed normally-off type static induction transistor

Abstract: This paper is mainly concerned with the state-of-the-art developments of the voltage-fed voltage-clamped type half-bridge topology of a new instantaneous resonant current vector-regulated high-frequency inverter, which efficiently operates at zero-current soft-switched quasi-resonant and load resonant tank circuit sub-resonant hybrid soft-switching schemes. This proposed multi-resonant inverter version using newly-developed high-frequency high-power normally-off type bipolar mode static induction transistors (B-SITs) is more suitable for a modern induction-heating and -melting power supply in industrial production plants. Its new conceptional operating principle is basically presented, including the control strategy, and its remarkable features are discussed. Its analytical results and performance evaluations are described through computer-aided simulation methods. A feasible breadboard of a trial inverter is originally demonstrated for the state-of-the-art induction heating power supply and is examined in an experiment from a practical point of view. >

Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude

Abstract: A beam current limiter for sensing and limiting the beam current in a particle accelerator, such as a cyclotron or linear accelerator, used in scientific research and medical treatment. A pair of independently operable capacitive electrodes sense the passage of charged particle bunches to develop an RF signal indicative of the beam current magnitude produced at the output of a bunched beam accelerator. The RF signal produced by each sensing electrode is converted to a variable DC voltage indicative of the beam current magnitude. The variable DC voltages thus developed are compared to each other to verify proper system function and are further compared to known references to detect beam currents in excess of pre-established limits. In the event of a system malfunction, or if the detected beam current exceeds pre-established limits, the beam current limiter automatically inhibits further accelerator operation. A high Q tank circuit associated with each sensing electrode provides a narrow system bandwidth to reduce noise and enhance dynamic range. System linearity is provided by injecting, into each sensing electrode, an RF signal that is offset from the bunching frequency by a pre-determined beat frequency to ensure that subsequent rectifying diodes operate in a linear response region. The system thus provides a large dynamic range in combination with good linearity.

Stability analysis of GTO-CSI induction machine drive using constant rotor frequency control

Abstract: The instability phenomena associated with GTO-CSI induction machine drive systems using a constant rotor frequency control scheme are investigated in this paper. It is indicated that a high frequency instability is caused by an LC resonance between machine leakage inductance and output filter capacitor through current feedback schemes. A low frequency instability is associated with the variations in rotor (slip) frequency and the output capacitor. Physical interpretations for these instabilities are presented and strategies for eliminating them are proposed. Time-domain simulations and experiments were performed to verify the analysis results.