Abstract: Disclosed is a variable inductance applying device using a variable capacitor, and a variable frequency generating device thereof. The variable inductance applying device includes: a first inductor whose both terminals are connected to an inductance applying terminal applying inductance to an external circuit; a second inductor inductively coupled to the first inductor; and a variable capacitor connected to both terminals of the second inductor, which varies inductance from the inductance applying terminal by changing capacitance. Therefore, the inductance to be applied to the external circuit can be varied by changing the capacitance of the variable capacitor. Since the variable capacitor rarely contains a resistance component, energy loss due to the resistance component hardly occurs. As a result, the variable inductance applying device has a high value of Q.

Abstract: An LC resonator (117; 122) for a voltage controlled oscillator (13; 116) has an inductive transmission line 31; 51), and input and output ports (33a-b; 53a-b) connected to the transmission line, wherein the transmission line is grounded (G) in at least one end portion thereof. The inductive transmission line has a plurality of connection ports (P) that are capable of being connected to each other or to ground in order to tune the resonance frequency of the LC resonator from one frequency band to another. Further, a trimming capacitor (C) may be interconnected in the transmission line in order to further tune the resonance frequency of the LC resonator. Preferably, the LC resonator is formed as a microstrip or strip line structure in essentially a C or S shape on a laminate substrate (101-103).

Abstract: CMOS LC tank circuits and flux linkage between inductors can be used to distribute and propagate clock signals over the surface of a VLSI chip or processor. The tank circuit offers an adiabatic behavior that recycles the energy between the reactive elements and minimizes losses in a conventional sense. Flux linkage can be used to orchestrate a number of seemingly individual and distributed CMOS LC tank circuits to behave as one unit. In one example, the distribution of a 45° separated multi-phase balanced oscillations over the surface of die 1.6 cm×1.6 cm at 10 GHz is expected to dissipate under 10 W and offers a potential to significantly reduce the road map predictions of 100 W. Simulations of several CMOS tank circuits indicate that the power dissipation can be reduced an order of magnitude when compared to conventional techniques. A passive flux linkage, mechanical, and finite state machine technique of frequency adjustment of an oscillator are described.

Abstract: CMOS LC tank circuits and flux linkage between inductors can be used to distribute and propagate clock signals over the surface of a VLSI chip or ?processor. The tank circuit offers an adiabatic behavior that recycles the energy between the reactive elements and minimizes losses in a conventional sense. Flux linkage can be used to orchestrate a number of seemingly individual and distributed CMOS LC tank circuits to behave as one unit. Several frequency-adjusting techniques are presented which can be used in an distributed clock network environment which includes an array of oscillators. A passive flux linkage, mechanical, and finite state machine technique of frequency adjustment of oscillators are described.

Abstract: A modulation circuit includes a microelectronic electromechanical system (MEMS) based resonant structure having a resonant frequency, an excitation input and an output. A control module is coupled to the excitation input of the MEMS based resonant structure. The control module modifies resonant characteristics of the MEMS based resonant structure to modulate the resonant frequency of the MEMS based resonant structure to produce a modulated signal at the output.

Abstract: Methods and systems are provided for reducing circuit area. Some embodiments provide electronic devices including an inductor formed from a path having two ends that loops substantially in a plane around a center area, wherein the path crosses itself at least two points and wherein the path defines an outer boundary of the inductor; and a circuit that is located within the outer boundary of the inductor and substantially within or adjacent to the plane. Other embodiments provide electronic devices including an inductor formed from a path having two ends that loops substantially in a plane around a center area, wherein the path defines an outer boundary of the inductor; and a circuit that is located within the outer boundary of the inductor and substantially within or adjacent to the plane, and wherein the circuit comprises a signal path that is rake-shaped and crosses the path of the inductor at substantially perpendicular angles.

Abstract: Disclosed is an ultra wide band signal generator. The ultra wide band signal generator generates a signal of a required frequency using a harmonic signal having a frequency range of a ultra wide band (UWB). The ultra wide band signal generator includes an active inductor for generating harmonic signals having power strengths substantially equal to each other within a non-linear operation range, the tunable active inductor capable of tuning a value thereof, an oscillator for amplifying and outputting the harmonic signals generated from the active inductor by frequency-transiting the harmonic signals into high frequency bands, and a filter for selectively outputting one of the harmonic signals output from the oscillator.

Abstract: The present invention discloses a dual-band voltage controlled oscillator (VCO), comprising a plurality of resonant circuits; an inductor module; a plurality of switches of current source; a buffer circuit; and a output port. The dual-band voltage controlled oscillator (VCO) according to the invention uses the current source in such two VCOs with different resonant frequencies as the switch device to combine the two VCOs and uses the common inductor module for the two VCOs to save the chip size.

Abstract: An oscillator circuit is formed of a differential LC resonant circuit formed of an L load differential circuit including inductance-variable portions and a capacitor element, and a positive feedback circuit formed of N-channel MOS transistors. The inductance-variable portion is configured to vary the inductance by selecting a plurality of switch circuits arranged between a plurality of arbitrary positions on a spiral interconnection layer and the input/output terminal, and thereby can control an oscillation frequency. The inductance-variable portions form an inductor pair when the switch circuit among the switch circuits coupled between the first input/output terminals is turned on together with the switch circuit.

Abstract: An LC tank structure. The structure, including a set of wiring levels on top of a semiconductor substrate, the wiring levels stacked on top of each other from a lowest wiring level nearest the substrate to a highest wiring level furthest from the substrate; an inductor in the highest wiring level, the inductor confined within a perimeter of a region of the highest wiring level; and a varactor formed in the substrate, the varactor aligned completely under the perimeter of the region of the highest wiring level. The structure may additionally include an electric shield in a wiring level of the set of wiring levels between the lowest wiring level and the highest wiring level. Alternatively, the inductor includes a magnetic core and alternating electrically non-magnetic conductive metal coils and magnetic coils around the core.

Abstract: A novel form of an integrated variable inductor uses an on-chip transformer together with a variable capacitor. The variable capacitor can either be a varactor or a switched capacitor array and is connected to the secondary coil of the transformer. By changing the capacitance at the secondary coil of a transformer, the equivalent inductance looking into the primary coil of the transformer can be adjusted. With another capacitor in parallel to the primary coil, two different modes of resonance inherently exist, and a very wide frequency tuning range can be achieved by combining the two modes.

Abstract: An oscillator circuit is formed of a differential LC resonant circuit formed of an L load differential circuit including inductance-variable portions and a capacitive element, and a positive feedback circuit formed of N-channel MOS transistors. The inductance-variable portion is configured to vary the inductance by selecting a plurality of switch circuits arranged between a plurality of arbitrary positions on a spiral interconnection layer and the input/output terminal, and thereby can control an oscillation frequency. The inductance-variable portions form an inductor pair when the switch circuit among the switch circuits coupled between the first input/output terminals is turned on together with the switch circuit.

Abstract: An amplifier comprises an amplifier circuit which comprises a first inductor as an impedance element for degeneration, and a control circuit which has a second inductor electro-magnetically connected to the first inductor, and changes a control current flowing through the second inductor to change an inductance value of the first inductor, thereby changing amplification characteristics of the amplifier circuit.

Abstract: A tunable clock distribution system is used to minimize the power dissipation of a clock distribution network in an integrated circuit. The tunable clock distribution system provides a tunable inductance on the clock distribution network to adjust a resonant frequency in the tunable clock distribution system. The inductance is tuned so that the resonant frequency of the tunable clock distribution system approaches the frequency of the clock signal on the clock distribution network. As the resonant frequency of the tunable clock distribution system approaches the frequency of the clock signal, the power dissipation of the clock distribution network decreases. Some embodiments also provide a tunable capacitance on the clock distribution network to adjust the resonant frequency of the tunable clock distribution system.

Abstract: A voltage-controlled oscillator device with an LC-resonant circuit, in particular for implementing integrated voltage-controlled oscillators for the lower GHz range, is disclosed. The device achieves continuous frequency tunability in a wide range in particular with a low level of phase noise and phase jitter. In the voltage-controlled oscillator, a second inductor can be periodically switched in parallel and/or in series with at least one first inductor of the LC-resonant circuit by way of a switching means actuated with the oscillator frequency. A control input of the switching means is connected to a variable dc voltage. In that respect the relationship of the duration of the conducting state and the duration of the non-conducting state of the switching means is variable within an oscillation period of the oscillator in dependence on the value of the control voltage.

Abstract: A voltage controlled oscillator having a wide oscillation frequency band, desirable carrier-noise characteristic, and desirable linearity of the oscillation frequency relative to a control voltage. The voltage controlled oscillator includes an oscillation unit and a control unit. The oscillation unit generates an output signal having an oscillation frequency corresponding to the control voltage in one of a plurality of oscillation frequency bands. The oscillation unit includes a switching unit for selecting one of the plurality of oscillation frequency bands in accordance with a switching signal. The control unit generates the switching signal in accordance with the control voltage.

Abstract: An RF VCO (260A) forms, in the preferred embodiment, a part of a dual mode mobile station (100). Also disclosed is a method for operating the VCO. The VCO is operated in a first frequency band using a first inductance (300A) that forms part of a first resonant circuit (parallel resonance), and the VCO is switched for operation to a second frequency band by the closing a switch (M5) that causes a second resonant circuit (serial resonance) to be inductively coupled to the first resonant circuit. The second resonant circuit includes a second inductance (300B), and preferably includes at least one frequency tunable component, such as a varactor (VR3, VR4), for adjusting the resonant frequency of the second resonant circuit. The second inductance is center tapped, and the switch, such as a MOS transistor, is coupled in series between two ends of the center tapped inductance. The first frequency band may include 3.6 GHz (a double frequency GSM band) and the second frequency band may include 4.

Abstract: A voltage-controlled oscillator in a phase-locked loop includes an LC oscillator. Control inductors are disposed of in the proximity of oscillator inductors, respectively. The control inductors are connected to a current source. By applying a control current to the control inductors, a mutual inductance is respectively induced between the oscillator inductors and the control inductors.

Abstract: One embodiment of the present invention provides an inductor with a variable inductance within a semiconductor chip. This inductor includes a primary spiral composed of a conductive material embedded within the semiconductor chip to provide a source of variable inductance. It also includes a control spiral composed of the conductive material vertically displaced from the primary spiral in neighboring layers of the semiconductor chip. This control spiral is magnetically coupled with the primary spiral so that changing a control current through the control spiral induces a change in inductance through the primary spiral. The inductor also includes a controllable current source coupled to the control spiral that is configured to provide the control current. One embodiment of the present invention includes a core surrounding the primary spiral and the control spiral in the semiconductor chip.

Abstract: A tuner includes an input terminal, first to fourth band-pass filters, an automatic gain controller, first to third amplifiers, first and second mixers, first and second voltage controlled oscillators, first and second PLL ICs, a reference oscillator circuit, and an output terminal. The second PLL IC and the reference oscillator circuit are connected through a capacitor and an amplifier. An amplifier for reference oscillation, included in the first PLL IC is connected to the reference oscillator circuit through an inductor that defines an inductance device.

Abstract: A voltage-controlled oscillator in a phase-locked loop includes an LC oscillator. Control inductors are disposed of in the proximity of oscillator inductors, respectively. The control inductors are connected to a current source. By applying a control current to the control inductors, a mutual inductance is respectively induced between the oscillator inductors and the control inductors.

Abstract: A method and apparatus for synthesizing high-frequency signals that overcomes integration problems while meeting demanding phase noise and other impurity requirements. In one embodiment, on-package oscillator circuit inductors are provided for band selection purposes, with no external package connection to connect off-package or external inductors to on-package inductance circuits. Multiple package electrical connection points may also be provided on-package to allow for selection of alternate oscillator inductance values during package assembly.

Abstract: In an oscillator circuit employing a pattern coil on a printed-wiring circuit board as a resonator circuit, in order to satisfactorily adjust dispersion in oscillation frequencies, an air-core coil wound by 0.5 turn and less than one turn is provided so as to be connected to the pattern coil in parallel and mounted on the printed-wiring circuit board. The oscillation frequency is adjusted by adjusting the angle of the air-core coil relative to the printed-wiring board.

Abstract: A variable frequency oscillator (VFO) circuit having an increased frequency tuning range to selectively obtain operating frequencies above and below a set frequency. The circuit includes a tank inductor connected in parallel with a tank capacitor for primarily defining the set oscillating frequency of the VFO circuit. A switchable capacitor is included for selectively providing a predetermined step-wise decrease of the oscillating frequency to a frequency value below the set frequency of the circuit, and a varactor is included for accommodating selective tuning of the oscillating frequency within a range of frequency values below the set frequency. The inventive circuit selectively includes a switchable inductance element which is selectively electromagnetically coupled to the tank inductor to decrease the overall inductance value of the VFO circuit and, thereby, selectively increase the oscillating frequency above the set frequency value.

Abstract: A multiple band voltage controlled oscillator capable of generating multiple operating frequencies, and a method of generating multiple operating frequencies, includes a tank circuit having a diode element and an impedance element with a radio frequency impedance in parallel with the diode element, a PIN diode connected across a portion of the inductance of the impedance element which selectively shorts the portion of the inductance of the impedance element when activated, a switch connected to selectively enable the PIN diode and correspondingly partially short the inductance of the impedance element, thereby scaling the radio frequency impedance of the tank circuit, and an oscillator circuit responsively connected to the PIN diode for varying the output of the voltage controlled oscillator based on the radio-frequency impedance present.

Abstract: A micromechanical variable/tunable inductor is disclosed. The present inductor comprises at least two elements capable of supporting spatial electromagnetic coupling and means for varying a geometrical relationship thereof. Varying the geometrical relationship between such elements varies the inductance of the inductor. In some embodiments, the geometrical relationship that is varied is the spacing between the two elements. The spacing is varied by creating a differential movement between such elements. In further embodiments, the present invention comprises resonant circuits incorporating such variable inductors, and oscillators including such resonant circuits.

Abstract: The present invention includes a Voltage Controlled Oscillator (VCO) having a resonant circuit capable of being quickly switched between two resonant frequencies in order to generate two different LO frequencies. In a preferred embodiment, the present invention includes a VCO having a dual-frequency resonant circuit attached to the VCO's resonant circuit input leads. The dual-frequency resonant circuit is constructed in a differential architecture in order to create a number "virtual ground" points within the circuit that nearly eliminate any ground currents, and thus minimize the time required to switch the resonant circuit between the two LO frequencies. The switching between two resonant frequencies is achieved by creating a short circuit across certain components within the circuit to eliminate them from the resonant circuit.

Abstract: A local oscillation circuit in a frequency converter circuit includes a resonant circuit, and a differential amplifier circuit connected to the resonant circuit. The differential amplifier circuit includes two transistors constituting a differential stage. One end of the resonant circuit is connected to the base of one transistor via a capacitive element, and to the collector of the other transistor via a capacitive element. The other end of the resonant circuit is connected to only the base of the other transistor via a capacitive element. Accordingly, an unbalanced oscillate operation is performed in the local oscillation circuit, leading to reduction of the phase noise caused by decrease in an oscillation output due to the trap phenomenon, and an improvement in reception quality.

Abstract: A digitally adjustable inductive element which can be implemented in an integrated circuit. The digitally adjustable inductive element can include a first inductor, and a digital inductance controller operatively coupled to the first inductor which can be utilized to vary the effective inductance of the first inductor. The digitally adjustable inductive element can include a second inductor operatively coupled to the first inductor, and a digital current controller operatively coupled to the second inductor. The digital current controller can include a number of transistors operatively coupled to the second inductor. The digitally adjustable inductive element can be utilized to create a tunable oscillator.

Abstract: An inductorless voltage controlled oscillator that may be fabricated using CMOS circuit elements. In one aspect, the present invention includes a synthetic inductance formed on a substrate and having first and second power supply terminals and a signal port. Additionally, an active admittance transformation network is formed on the substrate and coupled to the synthetic inductance and to the port. The synthetic inductance manifests an admittance at the port which has an inductive component and a positive real component. The active admittance transformation network transforms the positive real component of the synthetic inductance admittance to a negative real component and preserves the inductive character of the synthetic inductance admittance. The synthetic inductance can provide an effective Q of greater than twenty. The active admittance transformation network and the synthetic inductance cooperate to produce a voltage-variable oscillation frequency in excess of fifty megahertz.

Abstract: An article comprising a micro-machined, passively self-assembling inductor is disclosed. The inductor is fabricated using MEMS technology and advantageously utilizes materials compatible with CMOS such that inductor is monolithically integrable with a CMOS chip. The inductor includes passive self-assembly means by which the inductor loop is moved away from an underlying substrate, typically silicon, in the final steps of inductor assembly. Such passive self-assembly does not require separate actuation or monitoring steps.

Abstract: A microwave oscillator includes a waveguide that is short-circuited on one side and a diode arranged therein, which receives its supply voltage by way of a coupling pin passed through a waveguide wall. At least one adjustment pin, extends into the waveguide and is adjustable in its penetration depth, for tuning the oscillator frequency. Because the adjustment pin is aligned at an acute angle to the coupling pin, the oscillator frequency can be tuned very precisely.

Abstract: An integrated, tunable inductance network features a number of fixed inductors fabricated on a common substrate along with a switching network made up of a number of micro-electromechanical (MEM) switches. The switches selectably interconnect the inductors to form an inductance network having a particular inductance value, which can be set with a high degree of precision when the inductors are configured appropriately. The preferred MEM switches introduce a very small amount of resistance, and the inductance network can thus have a high Q. The MEM switches and inductors can be integrated using common processing steps, reducing parasitic capacitance problems associated with wire bonds and prior art switches, increasing reliability, and reducing the space, weight and power requirements of prior art designs.

Abstract: An active inductor oscillator includes a tank circuit for generating a first differential signal, a common-mode inverting differential buffer for generating a second differential signal in response to the first differential signal, and an integrating circuit for generating a third differential signal in response to the second differential signal. The third differential signal is applied to the tank circuit, and lags the first differential signal. A differential transistor pair in the tank circuit provides active inductance in response to the third differential signal, and a cross-coupled transistor pair in the tank circuit provides negative resistance that amplifies the first differential signal in response to the first differential signal. Currents through the tank circuit, buffer, and integrating circuit are essentially identical to one another and move in unison with an externally applied reference current that controls the oscillation frequency.

Abstract: An optically controlled oscillator utilizes a HEMT or a PIN diode as a photodetector and either a HEMT or HBT as an active inductor. The optically controlled HEMT active inductor provides a means for tuning the frequency of the oscillator. The optical receiver includes an optically tunable active inductor using a photodetector which includes a resonant tank circuit of an electronic oscillator to allow both optical/digital quench and unquench of an oscillator or digital AM detection with an improved signal to noise ratio, or optical FM modulation and analog AM detection by tuning/shifting the frequency of the oscillation through the detection of the optical light intensity.

Abstract: A variable-frequency oscillator configuration, in particular for tuners, includes a feedback network for an oscillator amplifier. The feedback network contains a series circuit formed by two resonant circuit inductors and a resonant circuit capacitor, connected in parallel with a series circuit formed by a further resonant circuit capacitor and a variable capacitor. A switching device is connected to a coupling node between the two inductors, for short circuiting the first resonant circuit capacitor and the resonant circuit inductor connected thereto under the control of a switching signal. The feedback network can consequently be switched over between two frequency bands and is symmetrical with regard to the high-frequency effect.

Abstract: A magnetic material for microwave, comprising a phase having garnet structure, said phase comprising a component represented by Formula I(A.sub.3-a Bi.sub.a)B.sub.x O.sub.y Formula Iwhere A represents a component comprising at least one element selected from yttrium (Y) and rare earth elements, B represents a component comprising Fe, a represents a number in the range of 0 to less than 2.00, x represents a number in the range of 4.76 to less than 5.00, and y represents a number satisfying an inequality 1.5(3+x).ltoreq.y.ltoreq.12.

Abstract: In order to improve the efficiency of a self-starting high-frequency generator, where for self-starting power is fed back from the anode circuit to the control grid of the grid-controlled electron tube used as amplifier element, the following measures are provided. An additional oscillating circuit (L.sub.A3, C.sub.A3) which is tuned to a multiple of the operating frequency (f.sub.1) is arranged in the anode circuit. An oscillating circuit (L.sub.G31, L.sub.G32, C.sub.G3) tuned to a multiple of the operating frequency (f.sub.1) is likewise arranged in the control-grid circuit. Components (L.sub.G31) belonging to the feedback circuit are at the same time components of the oscillating circuit arranged in the control-grid circuit.

Abstract: High-frequency, low-power CMOS oscillators having electrically-tunable tank circuits are disclosed. Electrically-tunable inductors assure highly efficient oscillator operation and can be adjusted after manufacture to assure high yields of high-precision oscillator circuits.

Abstract: This invention relates to an arrangement for driving a high-frequency oscillating tool arrangement (1) which includes, inter alia, a device (1a) whose form changes with a change in voltage, utilizing an electric drive circuit (2) constructed to generate alternating voltage which can be connected to the device and the frequency of which is adapted, through a first control circuit (7), to a value (C1, L1) which momentarily corresponds to the resonance frequency of the reactive element which varies during a working operation. The first control circuit (7) is constructed to control momentary frequency in dependence on momentary phase difference between the current and voltage values of the alternating voltage.

Abstract: An optically controlled active impedance element particularly suited to se as a tuneable inductive element for a microwave oscillator is disclosed. The optically controlled active inductive element is comprised of a circuit arrangement, preferably consisting of MESFET devices which exhibit a composite inductive characteristics, and whose inductance may be determined and controlled by direct illumination impinging on the MESFETs. The optically controlled active inductive element lends itself to being adapted to monolithic microwave integrated circuit (MMIC) applications and may find use in a wide variety of microwave circuits. Also disclosed, is an embodiment which used the optical controlled active impedance element, in a prescribed manner, to serve as a tuneable capacitor for use in various microwave circuits.

Abstract: An oscillator circuit is tunable by a tuning circuit which includes a spiral inductor disposed on a ferrite substrate. The oscillator circuit is tuned or modulated by varying a current through the spiral inductor.

Abstract: There is disclosed herein a driver system for an ultrasonic probe for allowing a user to have proportional control of the power dissipated in the probe in accordance with the position of power dissipation controls operable by the user and for automatically tuning upon user request such that the driving frequency is equal to the mechanical resonant frequency of said probe and such that the reactive component of the load impedance represented by said probe is tuned out. The system uses a tunable inductor in series with the piezoelectric crystal excitation transducer in the probe which has a flux modulation coil. The bias current through this flux modulation coil is controlled by the system. It is controlled such that the inductance of the tunable inductor cancels out the capacitive reactance of the load impedance presented by the probe when the probe is being driven by a driving signal which matches the mechanical resonance frequency of the probe.

Abstract: A tuning circuit (4) for a VCO includes a coarse tuning section (6) and a fine tuning section (7). The coarse tuning section includes three varactors (13, 14, 15) connected in series. These varactors together with their housings are designed to operate at considerably lower frequencies than the VCO, so that they behave as inductances at the VCO frequency. A capacitance (16) connected in parallel with the varactor inductances forms a resonant circuit therewith and serves to widen the tuning band of the VCO in adjustable manner. A capacitance (17) connected between the coarse and fine tuning sections adjusts the central oscillation frequency. An adjustable transmission line (12) in the fine tuning section adjusts fine tuning sensitivity.

Abstract: A sensing system including a sensing device with cooperating electrical components which move relative to each other in response to a sensed environmental parameter to yield a reactance signal, which is transmitted to a remotely located processor having an oscillator for receiving the transmitted signal and generating a transduced signal whose value corresponds to the value of the environmental parameter.

Abstract: Three series connected inverters (38, 40, 42) are attached to a tank circuit (18) which includes an inductance (12, 14) and a capacitance (16, 17). Negative (38) biases the inverters at the midpoint between the bistable low and high logic level states. Positive feedback from the second inverter (40) to the tank circuit induces oscillation in the tank circuit. The negative feedback is decoupled at the resonant frequency and the energy delivered to the tank circuit from the positive feedback maintains a low level oscillation in the tank circuit. Negative feedback around the three inverter digital circuit prevents lockup in the event of power loss or momentary short.

Abstract: A driver system for an ultrasonic probe using a tunable inductor in series with the piezoelectric crystal excitation transducer in the probe. The bias current through this flux moduation coil is controlled by the system such that the inductance of the tunable inductor cancels out the capacitive reactance of the load impedance presented by the probe when the probe is being driven by a driving signal which matches the mechanical resonance frequency of the probe. The resulting overall load impedance is substantially purely resistive. The system also adjusts the frequency of the driving signal to track changing mechanical resonance conditions for the probe at different power levels. This method of operation insures substantially maximum power transfer efficiency and substantially linear power control over a range of power dissipation levels.

Abstract: An integrated voltage controllable oscillator having a transistor for oscillation is further provided with a resonance circuit externally connected to two electrodes of the transistor for oscillation and including a variable capacitance element adapted to vary a resonance frequency of the resonance circuit, and a high impedance element connected between the variable capacitance element and the ground in a circuit adapted to supply a control voltage to the variable capacitance element.

Abstract: A battery charger comprises a self-oscillating inverter with saturable transformer means in its positive feedback circuit. The saturation flux density of the magnetic material used in this saturable transformer means determines the frequency of inverter oscillation. A permanent magnet is rotatably mounted adjacent the saturable transformer means and is used by way of cross-magnetization to adjustably affect the saturation flux density of the magnetic material, thereby correspondingly to adjust the frequency of oscillation: the more cross-magnetizing flux provided to the magnetic material from the permanent magnet, the smaller the saturation flux density and the higher the frequency of oscillation.The battery charging current is attained from the inverter's squarewave voltage output by way of a series-excited parallel-loaded tuned L-C circuit, thereby providing for a battery charging current of magnitude dependent upon the frequency of inverter oscillation.

Abstract: An automatic tuning circuit is provided for adjusting the frequency and phase of an oscillatory circuit in a power supply used for providing high frequency electrical energy to an electroacoustic converter. The oscillatory circuit includes an electrically variable inductance means in a feedback loop coupled between the output and an input of the oscillatory circuit and a switching device. The phase relationship of a signal indicative of the voltage across the switching device and a signal indicative of the state of the switching device and hence the current through the switching device is monitored. The inductance of the variable inductance means is adjusted responsive to the phase relationship of the signals indicative of voltage and current through the switching device for maintaining the two signals in phase during operation of the oscillatory circuit.