Abstract: A Pierce oscillator has been modified to replace the large capacitor with an amplifier element in order to make it more compact. A first amplifier element has a control terminal and a main current path extending between first and second output terminals. A network feeds back the signal at the first output terminal of the first amplifier to the control terminal of the first amplifier element and includes a series-arranged piezoelectric oscillation element. The oscillator also includes a reactive circuit element such as a resonant LC circuit or inductor (herein called an output dipole) coupled to the first output terminal of the first amplifier element and a DC current defining element coupled to the second output terminal of the first amplifier element.

Abstract: A voltage controlled oscillator having a reduced oscillation frequency-modulation sensitivity variation and having a positive modulation function is designed to: (a) reduce the modulation variation by making the rate of change in oscillation frequency with a certain change in a modulation signal generally constant with respect to a wide range of oscillation frequencies; (b) reduce the manufacturing cost by using only one varactor diode; and (c) reduce the cost of a system using the voltage controlled oscillator by eliminating the need for correction of the modulation variation on the side of a system using the oscillator. In a variable capacitance circuit of the voltage controlled oscillator, the cathode of a varactor diode is connected to a control voltage terminal and is also connected to a modulation signal input terminal by a coupling resistor and a voltage dividing resistor.

Abstract: A controllable-frequency oscillator has a first portion for generating a signal having a controllable frequency. The controllable-frequency oscillator has a second portion for controlling the frequency of the signal generated by the first portion in response to a first control signal. The controllable-frequency oscillator has a third portion for controlling the frequency of the signal generated by the first portion in response to a second control signal separate from the first control signal.

Abstract: A temperature-compensated quartz oscillator comprises a stabilized power supply circuit (1) for supplying a constant voltage, an oscillation circuit (2) comprising a quartz resonator (21) and a varicap (22), a temperature detecting circuit (3) for producing a detected voltage signal (V.sub.Temp) corresponding to an oscillator part temperature by the use of the temperature-voltage characteristic of a temperature detecting element located in the vicinity of the oscillation circuit (2), and a temperature characteristic compensating portion (4) for producing through analog processing of the detected voltage signal (V.sub.Temp) a varicap control voltage signal (V.sub.VR) to be supplied to the varicap (22).

Abstract: A control circuit includes: a temperature 30; a temperature sensing section 32; a memory 36, an amplifying section 31 to which the memory and the temperature sensor are electrically connected; a first D/A converting section 38 electrically interposed between the memory and the temperature sensing section; a second D/A converting section electrically interposed between the memory and the amplifying section 31, The amplifying section 31 includes: a polarity inverting circuit 33 connected to the temperature sensor; and a variable attenuator 34, an offset adjusting circuit 100, and an amplifying circuit 35 that are connected sequentially to the polarity inverting circuit. The amplifying section 31 is connected to a sample hold circuit 41 through a displacement buffering means 101. The memory has 8 or less working control voltage setting groups.

Abstract: A broadcast transmitter for generating low power modulated signals, especially for a wireless speaker system. A signal source such as a source of composite audio signals including left and right audio signals and a pilot signal are applied to a radio frequency signal oscillator. The radio frequency signal oscillator includes a bipolar transistor connected in a common base configuration, and having a stripline element as a frequency determinative component in the collector circuit of the bipolar transistor. The modulating signal is applied to the base of the bipolar transistor which modulates the collector junction capacitance of the transistor thereby frequency modulating the signal produced by the oscillator. Varactor tuning is provided for setting a nominal frequency of oscillation.

Abstract: The invention concerns oscillator circuits, more particularly coupling arrangements between an oscillator and an amplifier stage following the oscillator. The solution according to the invention optimizes the intensity of the coupling between the oscillator and the following amplifier stage so that the desired output level of the oscillator circuit is gained but the oscillator is loaded as little as possible. In the system according to the invention, the impedance value of the circuit element between the oscillator and the amplifier stage has been arranged to be automatically adjustable so that it is always adjusted to its smallest value, on which the desired output level of the oscillator coupling can still be gained. The coupling can, for example, be formed by means of a capacitance diode, the bias voltage of which is adjusted according to the direct voltage detected at the output level of the amplifier stage.

Abstract: An active circuit includes an amplifying transistor (102), a voltage reference (208), and an active bias circuit. The active bias circuit controls the operating point of the amplifying transistor, and includes a bias transistor (224) which is controlled by the voltage reference and the collector current of the amplifying transistor. As the temperature of the amplifying transistor changes, the tendency of the collector current to change is counter-acted by the bias transistor and the voltage reference.

Abstract: A voltage controlled oscillator including a resonator which generates an oscillation signal, a frequency of which is in response to a control signal, and an amplifier which amplifies the oscillation signal. Also included is a frequency adjusting mechanism, as well as a voltage control sensitivity mechanism. In one example, the resonator includes an input terminal to which the control signal is applied, a variable capacitance diode and a main inductor. The oscillation frequency adjusting mechanism includes a first variable capacitor, arranged in parallel with the main inductor of the resonator. In addition, the voltage control sensitivity adjusting mechanism includes a second variable capacitor arranged between the input terminal and the amplifying mechanism, and also arranged between a hot terminal of the variable capacitance diode and a hot terminal of the main inductor.

Abstract: A dual band oscillator circuit according to the present invention comprises an oscillator circuit portion that oscillates at a first frequency, an oscillator circuit portion that oscillates at a second frequency, a buffer amplifier circuit portion to which an output of the first oscillator circuit portion is input through a first stage-to-stage coupling element and an output of the second oscillator circuit portion is input through a second stage-to-stage coupling element. Operation is switched between the first and second oscillator circuits by an externally applied control voltage signal.

Abstract: An oscillator circuit (10) having an optimized start up time includes an inverting amplifier (12) coupled in parallel to a crystal (14), a first bank of capacitors (16) coupled to the crystal, and a second bank of capacitors (20) switchably coupled (18) in parallel to the frequency resonant network, wherein the second bank of capacitors has a higher capacitance load than the first bank of capacitors. The oscillator circuit may also include a processor (62) for controlling when the second bank of capacitors gets switched and coupled to the crystal.

Abstract: A voltage controlled oscillator has an active circuit, a resonant circuit coupled to the input node of the active circuit and an adjustable impedance circuit coupled to an output node of the active circuit. The impedance of the adjustable impedance circuit may be altered to tune the oscillation frequency of the oscillator. In one embodiment, the adjustable impedance circuit includes a varactor diode in series with a capacitor and means for varying the voltage across the varactor diode. An isolation circuit is coupled to an output node of the active circuit. In one embodiment, the isolation circuit is connected to a different output node than the adjustable impedance circuit is connected to.

Abstract: A bipolar negative resistance UHF oscillator having a voltage tunable resonator in its emitter circuit is operated at a fixed collector bias current and an RF detector is used as a convenient way to determine the RF current at which the oscillator is operating, by sensing the amplitude of the oscillator's output RF voltage across a constant load. An integrating error amplifier referenced to a desired detector output level responds to the actual detector output level to control the collector bias voltage for the oscillator and maintain the output of the oscillator at a fixed amplitude. Since the collector bias current is fixed, this keeps the operating point at fixed relation with respect to emitter cutoff. That relationship is chosen to be "just below" by initial selection of the constant collector bias current and the reference voltage used by the integrating error amplifier.

Abstract: An improvement on the phase-locked loop (PLL) circuit, in which an amplifier is disposed at the modulating signal input end of the PLL, and the output end of the amplifier is connected in series to a resistor and an inductor, followed by a resistor connected to a higher DC bias as well as a variable capacitance diode connected to ground. In such a way, the variable capacitance diode is under the higher bias and thus has a smaller capacitance change, while having its Q-value property opposite to the resonance curve formed by the crystal unit of an oscillator which is associated in parallel with the variable capacitance diode, thereby forming in a good compensation for the linearity of the circuit architecture and achieving an ideal frequency deviation and a reduced distortion caused by the modulation.

Abstract: This single voltage controlled oscillator for a PLL circuit has two control loops: a low noise ration is maintained by a main loop; while a wide frequency capture range is ensured by a sub-loop controlled by a one-chip microcomputer. The main control loop is a low gain loop with a narrow capture range that compares the phase of the output of the PLL circuit with the phase of a horizontal synchronous video signal supplied to a LCD display. The sub-loop is a high gain loop with a broad frequency range that includes a processor that monitors the lock on the main loop. When the lock is broken, the processor increments or decrements the voltage supplied to this sub-loop in one or more steps until the lock is reestablished, and the PLL circuit is again operating within the narrow capture range of the low gain loop.

Abstract: An oscillator circuit is provided for stabilizing the amplitude of a HF oscillation of an audio signal. In such an oscillator circuit, an audio signal having a frequency in the range of 20 Hz . . . 20 kHz is coupled into the oscillator circuit, is modulated with a high frequency and is emitted in the form of an RF audio signal having a frequency of more than 2 MHz. Such an oscillator circuit is used for instance in an infrared transmitting unit, wherein a low frequency audio signal is transformed into a higher frequency infrared signal. The higher frequency audio signals are transmitted via infrared channel to an appropriate receiving unit--for instance to infrared head phones--which comprises a receiving unit having an appropriate demodulator and preferably also a stereo-decoder in order to reproduce the low frequency audio signals.

Abstract: A crystal oscillation apparatus and a method of adjusting the same, comprising a crystal oscillating circuit, a frequency adjusting element coupled with the crystal oscillating circuit, and a control circuit for controlling voltage to be applied to the frequency adjusting element. The control circuit comprises a temperature sensor, a temperature detecting section coupled with the temperature sensor, a memory device coupled with the temperature detecting section, an amplifier to which the memory device and the temperature sensor are coupled, a first D/A converter between the memory device and temperature detection section, and a second D/A converter between the memory device and amplifier. The memory device has no more than 8 control voltage setting groups. Each of the control voltage setting groups has temperature detection data, amplitude setting data and offset voltage data.

Abstract: Device of the phase-locked loop type for demodulating a frequency-modulated signal. Device for frequency demodulation, using a phase-locked loop. According to the invention, for linearizing the variation of the frequency of a local oscillator (11) as a function of its control signal (Vb), a variable capacitance (Cv) is formed by an electronic module (20) which supplies the equivalent of a capacitance whose variation as a function of the control voltage (Vb) has a linearity deviation which is established for compensating the linearity deviation of the frequency of the oscillator as a function of the value of the capacitance (Cv).

Abstract: A temperature compensation circuit (10) for a crystal oscillator module (12) used in a communication device (200). An existing microcontroller (210) of the communication device (200) is used to provide temperature compensating digital data (30) for a crystal oscillator (18). The temperature compensating digital data (30) is converted to a temperature compensation signal (22) in a digital-to-analog converter (32) which controls the crystal oscillator frequency. The crystal oscillator module (12) includes an onboard voltage regulator (34) which supplies a characterized regulated voltage (36) to the digital-to-analog converter (32) such that the temperature compensation signal (22) from the digital-to-analog converter (32) is inherently corrected for voltage variations in the voltage regulator (34). Changes in the temperature compensation of the crystal oscillator (18) are allowed only when the communication device (200) is not transmitting or receiving.

Abstract: The present invention provides for a voltage-controlled crystal oscillator (VCXO) which, other than the crystal itself, is full integrated. The VCXO has a pre-amplifier block, a gain stage, a first MOS transistor, a first capacitor, a second MOS transistor, and a one second capacitor. The pre-amplifier block receives an input tuning voltage and the gain stage is connected across the terminals of the oscillating crystal. The first MOS transistor and first capacitor are connected between one of the terminals of the oscillating crystal and a reference voltage. The second MOS transistor and the second capacitor are connected between the second crystal terminal and the reference voltage. The gates of both MOS transistors are connected to the output node of the pre-amplifier block. The first and second MOS transistors connect the first and second capacitors to the first and second terminals of the gain stage for a portion of the time responsive to the input tuning voltage.

Abstract: The invention is related to an electrically tunable voltage-controlled oscillatory circuit, wherein the negative bias voltage (-Vcf) of a capacitance diode (5) needed for tuning the center frequency of the oscillatory circuit is generated on the basis of an electric oscillating signal (RFout) produced by the oscillatory circuit itself. Said oscillating signal is used for generating a negative voltage with a clamp/voltage multiplier type circuit (15) and it is adjusted to a desired value with an adjustment circuit (14), in which the values of the components (R2) can be permanently adjusted suitable in the tuning stage. Alternatively, the adjustment circuit (14) may include an active component (Q1) which can have an effect on the value of the negative bias voltage (-Vcf) during the use of the oscillatory circuit.

Abstract: A temperature compensation circuit (10) for a crystal oscillator module (12) used in a communication device (200). An existing microcontroller (210) of the communication device (200) is used to provide temperature compensating digital data (30) for a crystal oscillator (18). In this way, the crystal oscillator module (12) does not require an on-board memory which substantially cuts costs. The temperature compensation digital data (30) is converted to a temperature compensation signal (22) in a digital-to-analog converter which controls the crystal oscillator frequency. However, typical digital-to-analog converters are driven by voltage regulators which vary over temperature.

Abstract: An oscillator circuit is described which exhibits low phase noise characteristics and has special application in UHF and microwave technologies. The oscillator circuit of the invention includes a band pass filter having specific capacitor and inductor values which can be optimized so that the circuit has a loaded Q very close to the resonator's unloaded Q.

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 voltage-controlled oscillator is provided having a semiconductor integrated circuit and a piezoelectric resonator. A variable-capacitance diode may be connected in series with the piezoelectric resonator. The variable-capacitance diode may be further mounted a land of a lead frame. The piezoelectric resonator, variable-capacitance diode and lead frame may be resin molded into a single unit. In operation, a signal may be applied to a node located between the variable-capacitance diode and the DC-cutting capacitor.

Abstract: In a voltage-controlled LC oscillator, a series LC resonance circuit is connected between two transistor amplifying stages which provide low impedance input and output circuits for the LC circuit. The collector of the first transistor stage is connected through a coil to the operating voltage. The emitter of the second transistor stage is connected to the reference voltage through a coil. This will result in narrowband transistor stages and significant advantages in the power consumption and other characteristics of the oscillator.

Abstract: A band switchable resonant circuit for a voltage controlled oscillator has an inductive component in parallel with a plurality of varactor diodes. Some of the varactor diodes are selectively switchable to control the frequency range of circuit operation.

Abstract: The high frequency circuit includes an oscillator connected in a Colpitts configuration. Negative feedback to the oscillator is applied through an amplifier, both to stabilize the circuit and to permit frequency modulation of the carrier signal generated by the circuit. This feedback incorporates a capacitance to neutralize the Miller effect, thereby enabling it to operate at exceedingly high carrier frequencies. A variation of the circuit permits it to be simultaneously controlled by both a voltage and a current control signal. Also, by applying a frequency modulated carrier signal at a particular node of the oscillator, a demodulated output signal may be obtained.

Abstract: A temperature compensation circuit (10) for a crystal oscillator programmed by a single component (12), such as a resistor. The component (12) provides a voltage to an A/D converter (26). The digital signals (28) from the A/D converter (26) are divided and directed to separate signal generators (44,46,48,50,56) which control different aspects of the temperature compensation circuit (10). These aspects include a hot, cold, linear, balance and warp adjustment. The temperature compensation circuit (10) drives a varactor (18) which reactively loads a crystal oscillator (14) to compensate frequency over temperature. By using a single component (12) to program the circuit (10), an EEPROM is no longer needed which saves IC space and reduces IC processing steps, and the use of multiple external components to perform a compensation is avoided which further saves physical space.

Abstract: A resonance inductor of a resonant circuit is formed of a chip inductor and an inductance fine adjustment pattern. A resonance capacitor is formed of a plurality of chip layered capacitors connected in parallel to each other via connection patterns formed on a substrate. The connection patterns are sequentially disconnected to adjust the capacitance of the resonance capacitor. Then, the inductance fine adjustment pattern is partially removed to adjust the inductance of the resonance inductor.

Abstract: An oscillator (1) includes first frequency-determining elements (13-16) for providing a first oscillation frequency, at least second frequency-determining elements (23, 24) connectable to the first frequency-determining elements (13-16) via at least a switching diode (25, 26) for adjusting the oscillator (1) to a second oscillation frequency, the oscillator further having a supply circuit (27-44, 54) which includes at least a controllable current source (27-30), the supply circuit being coupled to the switching diode (25, 26) for optionally switching the switching diode between a conducting state and a blocked state, and having a current source (4) feeding the oscillator (1).

Abstract: A high power, low noise voltage-controlled oscillator (VCO) eliminates the drive-stage amplifier and costly surface-acoustic wave (SAW) inter-stage filter in a transmitter such as a cellular radiotelephone. The VCO includes a resonant circuit, an active part connected to the resonant circuit, and a buffer amplifier, connected to the active part, for isolating the VCO from a load connected to the buffer amplifier. The active part includes at least one transistor in a Colpitts configuration; capacitances connected in parallel with junction capacitances of the transistor, each capacitance having a value that is greater than a value of the respective junction capacitance with which it is connected in parallel; and a resistance for providing negative feedback at low frequencies. A second resistance may be provided for reducing the gain of the active part when oscillation starts.

Abstract: In an oscillator arrangement (VCXO), an oscillation loop (OSL) oscillates at, approximately, the fundamental frequency of a crystal (XTL) included therein. The output signal (Sosc) of the oscillator arrangement (VCXO) is a harmonic extracted from the oscillation loop (OSL). To vary the frequency of the output signal (Sosc), a tuning circuit (VAR) is included in the oscillation loop (OSL). A stage (FIL) in the oscillator arrangement (VCXO) prevents harmonic feedback into the oscillation loop (OSL). Such an oscillator arrangement (VCXO) can be tuned over a relatively large frequency range and has a monotonous tuning characteristic.

Abstract: An apparatus and method are disclosed for improving the stability of the frequency of vibration of an oscillator signal produced by an oscillator circuit. In a preferred embodiment of the present invention, a quartz crystal resonator is one arm of a bridge which generates a bridge signal which varies in accordance with the vibrating frequency of the resonator. A synchronous demodulator responds to the bridge signal for producing an error signal which is converted into a control signal. A control circuit receives the control signal and changes its reactance when the resonator is no longer vibrating at its unperturbed resonance frequency so that the vibration frequency of the resonator connected to the control circuit is returned to its resonant frequency. An automatic level control circuit is also included for controlling the drive level of the signal exciting the resonator.

Abstract: A Colpitts voltage-controlled oscillator is provided with a variable capacitance section 11 connected in parallel to a resonator 12, which is the inductance element of an inductance section 1. Variable capacitance section 11 is provided with varactors X1 and X2 having differing voltage/capacitance ratios. A fixed control voltage Vc is applied to the commonly connected cathodes of varactors X1 and X2. A control voltage Va which produces a reverse bias voltage (Vc-Va) is applied to the anode of varactor X1, and a control voltage Vb which produces a reverse bias voltage (Vc-Vb) independent of control voltage Va is applied to the anode of varactor X2. When control voltage Va is fixed, control voltage Vb is made the frequency control signal, and when control voltage Vb is fixed, control voltage Va is made the frequency control signal.

Abstract: In a digital temperature compensated crystal oscillator, ADC circuit and DAC circuit are combined into a data conversion circuit which comprises a first section for DA conversion, a second section for converting an analog temperature voltage signal into a digital form in cooperation with the first section, and a third section for supplementing the DA conversion of the first section and thereby generating an analog control voltage for a VCO from a digital temperature compensation data. There is further provided a switch circuit for connecting the output of the first section to either of the second and third section.

Abstract: Voltage controlled oscillator (VCO) circuits include a VCO and voltage regulator provided on an integrated VCO module, balanced control input for the VCO, buffering of the VCO and frequency multiplication of the VCO output signal. Such improved VCO circuits are especially useful in phase-locked loop (PLL) circuits. Improved PLL circuits are also provided, including a PLL circuit with separate analog and digital grounds.

Abstract: A system and method for establishing the frequency of a voltage controlled oscillator ("VCO") within narrowly defined frequency bands. The resonant circuit of the VCO uses selectable elements, such as varactor diodes, to establish the operating frequency band. The control voltage of the VCO is varied within a voltage range to adjust the VCO output frequency. A phase detector compares the VCO output to a reference signal. If the phase detector determines that there is an imbalance between the VCO output and the reference signal, then it produces a signal which indicates whether the VCO frequency should be increased or decreased to match the reference signal frequency. If the control voltage is outside of the voltage range, then the system allows the operating frequency band to be changed by varying the number of selectable elements in response to the phase detector signal.

Abstract: The correction circuit comprises a first quadrature phase comparator intended to receive as input two signals which are desired to be in quadrature and to have equal amplitudes. Phase adjustment means are firstly intended to correct the phase of at least one of the signal to re-establish a phase difference of 90.degree. therebetween. The correction circuit further comprises means to effectuate the sum and the difference of the signals which it receives as input and to supply the sum and the difference to a second quadrature phase comparator intended to supply as output a second error signal representative of the difference of the effective phase shift of these calculated signals and 90.degree.. The second error signal is finally supplied to amplitude adjustment means intended to correct the amplitude of at least one of said signals.

Abstract: The invention provides a piezoelectric oscillator including a semiconductor integrated circuit and a piezoelectric resonator or a voltage-controlled oscillator including a semiconductor integrated circuit, a piezoelectric resonator and another electronic component. The piezoelectric resonator has a cross-sectional shape of an ellipse or a track. The semiconductor integrated circuit and the electronic component are molded with a resin into a very thin unit.

Abstract: Both differential and single-ended band-switchable VCOs are described. The single-ended version of the voltage controlled oscillator in its most basic form includes a load, two transistors, two delay elements, and a switchable current source. The first transistor includes a collector, an emitter and a base coupled to the load to form an output terminal for providing an oscillator output signal. The first delay element is connected between the collector and the base of the first transistor. The second transistor includes a collector, an emitter and a base connected to the base of the first transistor. The second delay element is connected between the collector of the first transistor and the collector of the second transistor.

Abstract: An oscillator comprises a first inverter provided with a resonant feedback circuit, a second inverter having its signal input terminal at the same DC level as the signal input terminal of the first inverter, and a current source having a current supply terminal connected to the power supply terminals of the first and second inverters.

Abstract: The system and method for phase lock loop (PLL) gain stabilization uses a digital compensation technique to correct for the large amount of gain variation present in a voltage controlled oscillator (VCO) utilizing a varactor diode. AVCO is arranged with additional capacitance in parallel with the vatactor diode of the VCO. By using multiple capacitors, more or less capacitance can be switched into parallel with the vatactor diode. Gain variation is accomplished by switching capacitors into the circuit, and for each combination of capacitors used in the resonant inductance-capacitance (LC) circuit of the VCO, the gain of the phase detector in the PLL is adjusted simultaneously. The phase detector has a charge pump that drives a current into a loop filter having a capacitor with a fixed value. The gain adjustment is accomplished by varying the amount of current available from the charge pump to this filter capacitor.

Abstract: An oscillator (100) includes a tank circuit (102) coupled to a an active circuit (108). The feedback (104) provides the necessary feedback between the tank and the active circuit necessary for oscillation. The active circuit (108) is biased via a biasing circuit (106) and coupled out to a load via an external coupling (110). The active circuit (108) includes two transistors (124, 126) coupled to each other in a cascode configuration. Transistor (126) provides the collector current for transistor (124) while preventing it from entering saturation prematurely. The biasing circuit (106) provides sufficient current drain for the transistor (126) in order to provide for optimum phase noise and bandwidth performance of the oscillator 100.

Abstract: An automatic gain control circuit and method ensure feedback for oscillator circuitry fabricated on a single semiconductor chip to adapt to the Q value established by a resonator circuit connected to the oscillator circuitry, and to ensure that gain is maximized and linearity of operation preserved within the voltage rails of the power supply.

Abstract: A VCO circuit has a voltage variable capacitance CVD2 connected in series with or in parallel to a condenser C3 connected in series with an inductance L1, which constitutes a resonator of the VCO circuit. An adjustment voltage VD2 is applied to a cathode of the voltage variable capacitance CVD2, such that the relation between a control voltage VD1 and an oscillation frequency f0 of the VCO circuit is electrically adjusted to improve the fabrication yield.

Abstract: The output frequency (14) of an oscillator circuit (10) can be controlled by replacing at least one of the reactive components (40), such as a capacitor or inductor, with a synthesized element (22). The synthesized element creates a signal that corresponds to the response of the reactive component it is replacing. The synthesized element may be a current source (44), such as a field effect transistor, that is capable of operating at low voltages.

Abstract: A pullable overtone crystal oscillator (201) includes an impedance buffer (217) for buffering an input impedance (109) to an amplifier stage (203). This structure enables construction of an overtone oscillator with increased pullability because a drive level of a crystal (221) can be set independent of the input impedance (109) of the amplifier stage (203).

Abstract: An inexpensive voltage control type oscillator suitable for use with a mobile radio communication system within a predetermined frequency band range. The oscillator includes a resonance circuit and an oscillation stage formed on a printed wiring board and operating such that the oscillation frequency of the oscillation stage is varied within a predetermined frequency band range by varying the resonance frequency of a parallel resonance circuit included in the oscillation stage on the basis of a control voltage. The parallel circuit comprises a strip line connected in series with a bias resistor and a chip capacitor connected parallel to the strip line. The strip line has an inductance sufficiently larger than that of the resistor and the chip capacitor has a capacitance value so determined that the capacitor resonates at a predetermined frequency in cooperation with the strip line.

Abstract: The object of the invention is a voltage controlled oscillator with improved tuning linearity, which comprises an oscillating transistor (T, 1), a resonator circuit (C11, C12, 11, 12, 19, 20) formed by a capacitance diode (D, 20) and an inductance (L1, 19), whereby the resonator circuit is connected to one of the transistor's (T, 1) electrodes and defines together with the transistor's internal capacitance and external capacitances the oscillator output frequency provided by the transistor. The output frequency can be changed with an external control voltage (V.sub.cntrl) supplied to the cathode of the capacitance diode (D, 20), the control voltage having minimum and maximum values, whereby the oscillator output frequency (f.sub.vco) is arranged to change within a certain frequency band in accordance with the control voltage (V.sub.cntrl). The resonance circuit (RES) is arranged at the current draining electrode (collector) of the transistor to have an effect on the linearity between the control voltage (V.