Abstract: A fully digitally-controlled LC tank oscillator (DCO) uses a bank of more significant binary-weighted and/or less significant equally-weighted capacitors that are switched between only two voltage potentials. The time-averaged value of capacitance of predetermined less significant capacitors is determined by dithering between the two states to achieve a further refinement in the resolution of the resonating frequency.

Abstract: A differentially controlled variable capacitor includes two variable capacitors that are arranged effectively in parallel and receive differential input. The variable capacitors are coupled to a common node that is biased to a potential. For diode-type variable capacitors, the bias potential should ensure that the variable capacitors continue to operate as capacitors by preventing the diode device from becoming forward-biased. The differentially controlled variable capacitors are useful as tuning elements in circuits that require frequency control. A noise signal may be injected into the control signal of the variable capacitors. The effective parallel arrangement of the variable capacitors allows differential control of the effective capacitance value such that the noise signal does not alter the effective capacitance value.

Abstract: A circuit is disclosed which adjusts the phase of a signal within an LC sinusoidal or a ring or other capacitive oscillator. The circuit uses FETs as capacitors. The gates of the FETs are connected to the capacitive node of the oscillator. The variable voltage source changes the state of the FET from depleted to inverted mode or from inverted to depleted mode which in turn dramatically changes the capacitance of the FET. The change of state exists for only a few clock cycles, typically less than five cycles, so that only the capacitance within the oscillator is instantaneously affected which changes adds as incremental/decremental frequency to adjust only the phase of the oscillation frequency. In this fashion, the average oscillation frequency not affected.

Abstract: An oscillator has a resonator which includes at least one capacitor and at least one inductor. The resonator supplies a first signal of a first frequency at an output of the resonator. A frequency multiplier or a frequency divider is connected, via an input thereof, to the resonator output. The frequency multiplier or frequency divider supplies a second signal of a second frequency at an output of the frequency multiplier or frequency divider. The second frequency is n times or 1/n times (n≧2 and integer) the first frequency. A tuned circuit is part of the resonator and forms a short circuit or an open connection for the second frequency.

Abstract: Method and circuitry for implementing VCOs with improved frequency band switching use differentially-coupled varactors to implement the different frequency bands. According to a specific embodiment, one side of a varactor couples to the tank circuit and the other side is coupled either to ground or to the positive power supply VDD without introducing any series parasitic resistance.

Abstract: A voltage controlled oscillator for wide range tuning bandwidth includes a transistor with a voltage tunable resonant circuit connected to an emitter of the transistor and inductive elements connected to the collector of the transistor. The collector is fed back to the base of the transistor. The feedback path includes the series connection of two capacitors and a resistor. A circuit node between the capacitors is inductively coupled to the base of the transistor.

Abstract: A voltage-controlled oscillator has a structure that is very compact and prevents characteristic deterioration. The voltage-controlled oscillator includes a first resonant circuit resonating in a first frequency band, a second resonant circuit resonating in a second frequency band that is higher than the first frequency band, an oscillation circuit oscillating at a resonance frequency of each of the first and second resonant circuits, an amplifying circuit amplifying an oscillation signal transmitted from the oscillation circuit, a control terminal applying a control voltage to each of the first and second resonant circuits, a power-source terminal commonly connected to the oscillation circuit and the amplifying circuit, and an output terminal outputting a high frequency signal.

Abstract: A circuit and method are disclosed herein for a crystal oscillator, wherein the Q of the resonant network is not reduced through the loading effects of the oscillator's resistive bias network. The oscillator is configured as an operational transconductance amplifier (OTA) coupled to the resonant network. The OTA creates a negative resistance, which compensates for energy lost to resistance within the resonant network, thereby sustaining oscillation at the resonant frequency. Instead of using bias resistors to set and maintain the operating point of the oscillator, another OTA (with a high output impedance) injects a current into the resonant network to bias the oscillator. Advantageously, this technique avoids the reduction in Q that occurs when bias resistors are connected across the high effective parallel resistance of the resonant crystal. The higher Q benefits frequency stability and phase jitter characteristics of the oscillator.

Abstract: An oscillator circuit is described and has an oscillator core with at least one inductance and, connected thereto, a first and second capacitance. A deattenuator is coupled to the oscillator core and has two transistors, which are cross-coupled to one another in a non-direct-electrical coupling. The respective load terminal of a respective transistor is directly connected to a reference-ground potential terminal. The non-direct-electrical, for example inductive, coupling of the transistors in combination with the transistors directly connected to ground enables a greater modulation capability and also a smaller phase noise of the oscillator circuit. In this case, the transistors are operated as current switches. In preferred embodiments, the oscillator circuit has a regulating circuit for a bias voltage and an operating-current setting.

Abstract: An oscillator provides output signals over a range of oscillating frequencies includes an resonant circuit, at least one active circuit device operatively coupled to the resonant circuit to supply energy to the resonant circuit, and at least one unidirectional device coupled to the active circuit device. The unidirectional device permits current to flow between the active circuit device and the resonant circuit when the active circuit device adds energy to the resonant circuit, and impedes a drain of energy from the resonant circuit due to increased output signal amplitude.

Abstract: The present invention generally relates to voltage-controlled oscillators. More specifically, the present invention relates to method and circuitry for implementing a differentially tuned varactor-inductor oscillator. In one exemplary embodiment, the present invention includes an LC tank circuit having a couple of terminals, a first and second capacitors, and a first and second varactors. The first and second varactors are connected in series forming a first and a second node. The first capacitor connects the first node and one terminal of the LC tank circuit. The second capacitor connects the second node and the other terminal of the LC tank circuit. A pair of differential input control signals is applied across the first and the second varactors, respectively, to tune the LC tank circuit thereby generating an oscillator output.

Abstract: A variable frequency oscillator which exhibits low phase noise by increasing the quality factor of the resonator in the oscillator circuit. This is achieved by employing multiple means of decoupling the resonator from all elements and circuits to which the resonator is connected. For example, the resonator is decoupled from the whole oscillator circuitry by connecting the oscillator to a tap on the resonator which reflects the oscillator as a lighter load across the entire resonator. The resonator is further decoupled from the emitter to the base junction circuitry by placing a impedance network between the base of the transistor and the ground. Additional decoupling circuitry is employed to reduce the loading of the resonator due to the external oscillator load.

Abstract: This invention relates to an oscillator that includes first and second switching elements that each have a control terminal, and first and second conduction terminals. The control terminal of the second switching element is coupled to the first conduction terminal of the first switching element, and the control terminal of the first switching element is coupled to the first conduction terminal of the second switching element. The oscillator also may include first and second capacitive elements, first and second inductive elements, and a resistive element. The first capacitive element may be coupled between the control terminal of the first switching element and a first reference node, and the second capacitive element may be coupled between the control terminal of the second switching element and the first reference node.

Abstract: In a voltage controlled oscillator for switching oscillation frequency bands by supplying a band switching signal to an LC resonator circuit that is connected in a phase locked loop having a phase comparator and a loop filter and sets oscillation frequencies, the LC resonator circuit includes at least two inductor elements the connection and non-connection of a part of which are switched in response to a band switching signal and a capacitor element in which a voltage variable capacitor element whose capacitance value is adjusted in response to the control voltage from the loop filter is connected in series to impedance elements acting as a composite element that exhibits a capacitance value in oscillation frequency ranges. With this arrangement, when an oscillation signal is selectively output in a high or low frequency band by switching the LC resonator circuit, the voltage controlled oscillator can increase the difference between the rates of change Kv in the high and low frequency bands.

Abstract: Monolithic integrated circuit oscillators, complementary metal oxide semiconductor (CMOS) voltage-controlled oscillators, integrated circuit oscillators, oscillator-forming methods, and oscillation methods are described. In one embodiment, a monolithic integrated circuit oscillator is provided and includes a semiconductive substrate. A field effect transistor is supported by the semiconductive substrate and an oscillator circuit is connected therewith. The oscillator circuit preferably comprises an inductor which is supported by the substrate and has an inductance value greater than or equal to about 4 nH. In another embodiment, a complementary metal oxide semiconductor (CMOS) voltage-controlled oscillator is provided and includes a metal oxide semiconductor field effect transistor (MOSFET) received by and supported over a silicon-containing substrate. The transistor has a gate, a source, and a drain.

Abstract: A drive circuit for driving the transmitter windings of an inductive position transducer includes an oscillating power source. A resonator section is connected to the power source. The resonator section includes an impedance transforming section, a transmitter winding of the inductive position transducer, and feedback loops which cause the power source to oscillate at the resonator frequency. The resonator operating frequency and the load impedance imposed on the power source by the resonator can be independently selected. In various exemplary configurations of the drive circuit, the resonator operating frequency adapts to variations in the impedance of the transmitter windings. The drive circuit is particularly well-suited for driving low-impedance and/or miniaturized inductive position transducers with enhanced efficiency and accuracy. In various exemplary configurations of the drive circuit, the peak operating voltage of the transmitter windings can exceed the power supply voltage.

Abstract: The present invention provides an oscillator such as a voltage controlled oscillator (VCO) that can supply more stable frequency signals in the presence of strong magnetic coupling caused by external magnetic perturbations. According to one embodiment of the invention, an oscillator is presented and comprises an amplifier and an LC circuit connected to the amplifier. In the LC circuit, a first pair of inductors includes first and second inductors and a second pair of inductors includes third and fourth inductors. The first and second pairs are arranged such that the first and fourth inductors are on a first side and the second and third inductors are on a second side. In one arrangement, the inductors are positioned such that a center between the first and second inductors substantially overlap a center between the third and fourth inductors.

Abstract: A control voltage Vin that has been input is sequentially reduced at NMOS's 111˜113 constituting means for voltage reduction. The individual voltages resulting from the voltage reduction are applied to control electrodes of MOS varactors 211˜213 constituting voltage-controlled variable-capacitance elements which are connected in parallel and, thus, the capacitance values of the individual MOS varactors 211˜213 are determined. An LC resonance circuit constituted of the MOS varactors 211˜213 and a coil 22 resonates at a specific frequency, NMOS's 23 and 24 constituting means for switching engage in on/off operation and oscillation occurs at an oscillation frequency corresponding to the voltage Vin resulting in an oscillation signal output through output terminals 3 and 4.

Abstract: A method of fast start and/or fast termination of a radio frequency resonator, which has a coil, a capacitor and two switches with internal resistance wherein one end of the switches is connected to a junction of the coil and the capacitor where a RF voltage is provided, and another end of each switch is connected to high voltage power supplies with opposite polarities, a fast start being achieved by closing one of the switches for a short period of time for fast start, and a fast termination being obtained by closing both switches for a while.

Abstract: A dual band voltage controlled oscillator that has low phase noise. The oscillator includes two voltage controlled oscillators that are each coupled to a tank circuit for adjusting the output frequency. One voltage controlled oscillator operates at a low frequency and one operates at a high frequency. Both voltage controlled oscillators are coupled to a combiner circuit that provides the oscillator output signal. A low frequency bandstop filter is coupled to the output of the second voltage controlled oscillator. The low frequency bandstop filter operates so as to reject the low frequency.

Abstract: An operational amplifier oscillator uses an operational amplifier as a low impedance driver for a resonator, the output from the operational amplifier being a voltage signal at the desired frequency. The operational amplifier has positive and negative feedback paths, with the negative feedback path having a first resistor for driving the impedance at the negative input to a small value when the voltage signal is near a zero crossing and an anti-parallel diode limiter in parallel with the first resistor with an optional series second resistor for driving the impedance at the negative input even smaller when the voltage signal swings away from zero. The positive feedback loop includes a series diode limiter or optional voltage divider. Phase noise is minimized by coupling a filter between the output and the positive feedback path to block the low frequency noise from the positive input of the amplifier.

Abstract: Recent trends have seen the desire for lower and lower supply voltages in radio frequency (RF) components as this leads to lower power consumption and, therefore, longer battery life. As well, lower voltages and less current means that mobile products can be made to require fewer battery cells leading to lighter, more compact devices. The present invention discloses a novel topology for providing a low-voltage voltage-controlled oscillator (VCO). The novel topology is based on the negative transconductance oscillator. However, the novel topology of the invention eliminates transistor ‘stacking’ in the oscillator circuit, thereby allowing the oscillator circuit to be operated at a supply voltage only slightly higher than the turn-on voltage for a single transistor.

Abstract: Methods and apparatus to control and enhance the quality factor of a tank circuit and oscillators having a tank circuit by feeding back a voltage to the tank circuit in opposition to the losses in the tank circuit. In an exemplary embodiment, a degenerate common emitter stage, responsive to the voltage across a differential circuit, has magnetically coupled inductors coupling voltages back to a differential tank in opposition to the IR voltage losses in the differential tank circuit. The amount of feedback may be controlled by the bias on the common emitter stage. Various embodiments are disclosed.

Abstract: The present invention, generally speaking, allows for a substantial reduction in oscillator phase noise by modifying the transfer function of a portion of the oscillator, e.g., by adding a zero to the transfer function. Modifying the transfer function reduces the open-loop gain of the oscillator but achieves a desired phase compensation, allowing the oscillator to be operated at the resonance of the resonator instead of off resonance. In an exemplary embodiment, the transfer function is modified by choosing a capacitance value such that, instead of operating as a bypass at the frequency of interest, adds a zero to the transfer function of the oscillator and causes a change in frequency characteristics, achieving an increase in the effective Q of the oscillator. This increase in effective Q translates directly into reduced phase noise. Phase noise improvement in the range of 3dB has been demonstrated.

Abstract: The present invention provides an oscillator such as a voltage controlled oscillator (VCO) that can supply more stable frequency signals in the presence of strong magnetic coupling caused by external magnetic perturbations. According to one embodiment of the invention, an oscillator is presented and comprises an amplifier and an LC circuit connected to the amplifier. In the LC circuit, a first pair of inductors includes first and second inductors and a second pair of inductors includes third and fourth inductors. The first and second pairs are arranged such that the first and fourth inductors are on a first side and the second and third inductors are on a second side. In one arrangement, the inductors are positioned such that a center between the first and second inductors substantially overlap a center between the third and fourth inductors.

Abstract: A resonant oscillator circuit includes an active device and a resonator that causes the active device to oscillate at a resonant frequency of the resonator. The active device includes one or more transistors that are DC biased using one or more resistors. The bias resistors generate thermal noise that is proportional to the resistance value. An external inductor circuit is connected across the output terminals of the active device and in parallel with the resonator. The external inductor circuit shorts-out at least some of the thermal noise that is generated by the bias resistors, and thereby reduces the overall phase noise of the resonant oscillator.

Abstract: A differential voltage-controlled oscillator (VCO) employs a pair of accumulation-mode varactors driven with a differential control voltage to generate a differential oscillating waveform. The differential control voltage is formed from a pair of level-shifted input differential control voltage components. Level shifting of the input control voltages and driving the varactors with a differential control voltage allows for biasing of the varactors over a substantial range of capacitance variation. Such differential VCO may be employed within a phase-locked loop (PLL) circuit, with the pair of input control voltages being provided by the loop filter of the PLL circuit. The differential VCO comprises a differential control voltage to voltage converter (CV2VC) coupled to an LC-tank VCO. To improve common-mode noise rejection of the LC-VCO, the inductors of the LC-tank may be AC-coupled to the supply voltage, and the output differential oscillating waveform may be AC-coupled to the LC-tank through capacitors.

Abstract: It is an object of the present invention to provide the voltage controlled oscillation circuit preventing the influence of a capacitor in the output side of the loop filter connected to a control voltage terminal. A voltage controlled oscillation circuit comprising of an amplifier circuit, a resonance circuit, a varactor diode, a choke element whose one end is connected to the cathode of a varactor diode, a capacitor connected between the other end of the choke element and a ground, and a resistor connected between the other end of the choke element and a control voltage terminal. A sub-resonance of the resonance system of the voltage controlled oscillation circuit due to the capacitor in the output side of the loop filter connected to the control voltage terminal can be eliminated, the abnormal oscillation of the voltage controlled oscillation circuit can be prevented, and the relationship between the oscillation frequency and the control voltage exhibits almost linear.

Abstract: A voltage controlled oscillator (200) has a tank circuit (210) with a first varactor diode (201), a transistor (225), a serial arrangement of a capacitor (202) and a second varactor diode (203) that is via a feedback node (215) coupled to the transistor; the capacity of both first and second varactor diodes is controlled by a common tuning voltage (VTUNE)

Abstract: A VCO system for equalizing a positive frequency deviation and a negative frequency deviation by using two varactors is described. The VCO system includes an active circuit and an oscillating circuit. The active circuit includes a first input, a second input coupled to ground and an output. The oscillating circuit is coupled to the output of the active circuit, including: a first varactor controlled by a first variable voltage; a second varactor controlled by a second variable voltage, connected in parallel to the first varactor; and an inductor connected in parallel to the first varactor and to the second varactor. An output signal of the oscillating circuit is fed back to the first input of the active circuit. The output signal of the oscillating circuit has a variable frequency in response to first and second variable voltages of the first and second varactors, respectively.

Abstract: An oscillator which oscillates at a predetermined frequency includes a first inverting amplifier and a second inverting amplifier connected in antiparallel with each other, a surface acoustic wave resonator connected in parallel with one of the first inverting amplifier and the second inverting amplifier, and a filter connected between the first inverting amplifier and the second inverting amplifier for blocking a direct-current signal while allowing a signal of the predetermined frequency to pass.

Abstract: A circuit for conditioning an input control voltage signal that is used to drive an LC tank oscillator in a phase locked loop (PLL). The conditioning circuit includes a two-stage amplifier including a first stage amplifier connected to a second stage comprising an active cascode circuit, a diode-connected transistor and a resistor tied to a reference voltage (e.g. ground). The first stage amplifier receives a control voltage input signal, which would typically be produced at the output of a loop filter in a PLL, and produces a conditioned control voltage output signal at its output, which is connected to the drain of the diode-connected transistor. The purpose of the amplifier is to lower the impedance of the conditioned output signal, which is then used to drive the LC tank oscillator, wherein the series resistor acts both to lower the impedance and to act as the degenerating resistor for the diode-connected transistor.

Abstract: A voltage controlled oscillator (38) includes an LC tank (20) and a capacitor bank (21). LC tank (20) includes an inductor (12) and a varactor (14). The capacitive output of the varactor is controlled by a control voltage &ngr;. To electronically tune the voltage controlled oscillator, a set of capacitors (24) in the capacitor bank (21) are enabled by a digital control signal based on a frequency comparison with a desired frequency. Once the capacitor bank is set, the frequency can be locked at the desired frequency by the phase lock loop.

Abstract: A Voltage Controlled Oscillator (VCO) with the ability to tune its operating frequency over a wide range using a limited control voltage range. The VCO implements a novel resonant circuit that provides the wide frequency tuning range and simultaneously provides increased immunity to induced low frequency noise. The resonant circuit utilizes an element configuration that includes high pass filters on each input to the resonant circuit. Varactor diodes are used to couple a conventional tuning circuit to the remainder of the resonant circuit. This configuration allows the resonant frequency to tune over a wide range using a limited control voltage range.

Abstract: A control voltage Vin that has been input is sequentially reduced at NMOS's 111˜113 constituting means for voltage reduction. The individual voltages resulting from the voltage reduction are applied to control electrodes of MOS varactors 211˜213 constituting voltage-controlled variable-capacitance elements which are connected in parallel and, thus, the capacitance values of the individual MOS varactors 211˜213 are determined. An LC resonance circuit constituted of the MOS varactors 211˜213 and a coil 22 resonates at a specific frequency, NMOS's 23 and 24 constituting means for switching engage in on/off operation and oscillation occurs at an oscillation frequency corresponding to the voltage Vin resulting in an oscillation signal output through output terminals 3 and 4.

Abstract: An inverter includes a fourth order impedance network coupled between the output and the input of an amplifier, causing the inverter to oscillate and produce a high voltage at an output of the impedance network. The impedance of one portion of the impedance network is preferably at least ten times the impedance of a second portion of the impedance network at the frequency of oscillation.

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: In a voltage controlled oscillator for switching oscillation frequency bands by supplying a band switching signal to an LC resonator circuit that is connected in a phase locked loop having a phase comparator and a loop filter and sets oscillation frequencies, the LC resonator circuit includes at least two inductor elements the connection and non-connection of a part of which are switched in response to a band switching signal and a capacitor element in which a voltage variable capacitor element whose capacitance value is adjusted in response to the control voltage from the loop filter is connected in series to impedance elements acting as a composite element that exhibits a capacitance value in oscillation frequency ranges. With this arrangement, when an oscillation signal is selectively output in a high or low frequency band by switching the LC resonator circuit, the voltage controlled oscillator can increase the difference between the rates of change Kv in the high and low frequency bands.

Abstract: In the previously known processes, the oscillating circuit amplitude decays exponentially after the excitation voltage has been interrupted. Upon switching the excitation voltage on again, the oscillation first has to be built up. This reduces the data transmission rate of transmission plants which are operated by intermittently working oscillating circuits.

Abstract: An electric potential of an epitaxial layer 2A provided under a bonding pad 5 to which a resonance circuit for a VCO is to be connected is fixed to a predetermined (Vcc) electric potential through a resistor 6 in a conventional floating state. Consequently, a speed of a change in the electric potential of the epitaxial layer 2A is increased and a value of a parasitic capacity is stabilized quickly. Consequently, a drift can be improved when a power supply is turned ON.

Abstract: It is an object of the present invention to provide the voltage controlled oscillation circuit preventing the influence of a capacitor in the output side of the loop filter connected to a control voltage terminal. A voltage controlled oscillation circuit comprising of an amplifier circuit, a resonance circuit, a varactor diode, a choke element whose one end is connected to the cathode of a varactor diode, a capacitor connected between the other end of the choke element and a ground, and a resistor connected between the other end of the choke element and a control voltage terminal. A sub-resonance of the resonance system of the voltage controlled oscillation circuit due to the capacitor in the output side of the loop filter connected to the control voltage terminal can be eliminated, the abnormal oscillation of the voltage controlled oscillation circuit can be prevented, and the relationship between the oscillation frequency and the control voltage exhibits almost linear.

Abstract: An oscillator with reduced phase noise. The oscillator includes a resonance circuit and an amplifying circuit. The amplifying circuit has an amplifier. An impedance element having a frequency characteristic is connected to the amplifier and, therefore, the power amplification of the amplifying circuit is decreased by at least 3 dB in a frequency band lower than about 0.5 times an oscillating frequency f0 or higher than about 2f0, as compared to the power amplification of said amplifying circuit at the oscillating frequency f0.

Abstract: An oscillator circuit for use with a wire-loop inductive sensor and method for use. The oscillator circuit highly attenuates common-mode noise detected by the wire-loop and differential noise from both ambient and crosstalk sources are filtered by active isolation.

Abstract: A tuning signal is injected into an LC tank circuit oscillator, e.g., through an impedance (either reactive, inductive, capacitive and/or resistive) to tune the phase and/or frequency of the LC tank circuit oscillator. A negative resistance is included in parallel with the LC tank circuit oscillator to compensate for losses in the LC tank circuit, and a bias signal is provided to power the operation of the LC tank circuit. Multiple LC tank circuit oscillators may be used to provide stable multiplied or divided frequencies. In another embodiment, the nominal frequency of the LC tank circuit oscillator may be adjusted using a varactor or other voltage-controlled element in the LC tank circuit oscillator under the control of, e.g., the output of a separate PLL loop including another LC tank circuit oscillator. In one application, the injection tuned LC tank circuit forms a clock recovery cell using a clock signal embedded in a NRZ (Non Return to Zero) pseudo-random data stream.

Abstract: To obtain means for suppressing a jump phenomenon to a B mode in a Colpitts oscillator using an SC-cut crystal unit. In a Colpitts oscillator including a piezoelectric resonator and an amplifier circuit, a series resonance circuit and a parallel resonance circuit consisting of an inductance and a capacitance are inserted into an oscillation loop, and the frequency of the series resonance circuit is set in the vicinity of the oscillation frequency of the oscillator, and the frequency of the parallel resonance circuit is set in the vicinity of an unwanted oscillation frequency of the oscillator, thereby to suppress the unwanted oscillation.

Abstract: A selectable oscillation circuit includes a first oscillation circuit, a second oscillation circuit, and a selector circuit. The selector circuit selectively switches on and off the first oscillation circuit and the second oscillation circuit, in accordance with the provision of a selector signal, to selectively switch between two communicating modes, with low-power consumption.

Abstract: A voltage controlled oscillator includes an amplifier having a positive feedback construction, configured to output an oscillation signal of a frequency corresponding to a control voltage supplied to a variable capacitor of a tank circuit having an inductor and the variable capacitor, and a variable current source configured to change an operation current supplied to the amplifier according to the control voltage. When a certain oscillation frequency at which phase noise becomes minimum is set as a reference point, the variable current source increases the operation current supplied to the amplifier as the oscillation frequency becomes lower than the certain oscillation frequency, or decreases the operation current supplied to the amplifier as the oscillation frequency becomes higher than the certain oscillation frequency. With this construction, a voltage controlled oscillator having a stable and sufficiently suppressed phase noise characteristic can be realized irrespective of the oscillation frequency.

Abstract: ? An RF Voltage Controlled Oscillator (VCO) design having improved power supply noise immunity. More particularly, a VCO resonant circuit that provides a high circuit Q, immunity to noise, and is tunable over multiple distinct bands. The resonant circuit is implemented in conjunction with an integrated circuit oscillator that requires a tuned circuit to determine the frequency of operation. When the integrated circuit oscillator is used as a Local Oscillator (LO) within a wireless phone it is subjected to numerous sources of power supply noise. In a Code Division Multiple Access (CDMA) wireless phone system the power supply to portions of the RF transmit path are cycled on and off depending on the transmitted data rate. The present invention provides an oscillator with increased immunity to the noise induced on the power supply due to power supply cycling.

Abstract: An oscillator has a resonator which includes at least one capacitor and at least one inductor. The resonator supplies a first signal of a first frequency at an output of the resonator. A frequency multiplier or a frequency divider is connected, via an input thereof, to the resonator output. The frequency multiplier or frequency divider supplies a second signal of a second frequency at an output of the frequency multiplier or frequency divider. The second frequency is n times or 1/n times (n≧2 and integer) the first frequency. A tuned circuit is part of the resonator and forms a short circuit or an open connection for the second frequency.

Abstract: In order to provide an oscillation circuit that is capable of achieving stable oscillation over a large frequency range, oscillating operation is carried out by connecting an LC resonance circuit, of which resonance frequency is adjustable, to the collector of a pair of transistors that function as 3-terminal active element, and feeding back the resonance signal of the LC resonance circuit to the base of the pair of transistors. At this time, a voltage appearing across both terminals of the LC resonance circuit is converted into a current by a Q-factor tuning voltage-current converter circuit, and the current is fedback to the LC resonance circuit thereby changing the Q factor of the LC resonance circuit.