Abstract: A two-stage direct conversion receiver. A first mixer (13) converts the incoming signal to an intermediate frequency (IF) signal. A second mixer (16) converts the IF signal to a baseband signal. A detector (17), receiver logic circuit (18), and alerting device circuit (19) act upon the baseband output signal. A two port oscillator (14) provides a fundamental frequency output (FO) and a tripled output frequency (3 FO). The tripled output frequency is again tripled (9 FO) by a frequency multiplier (15) and is provided as a mixing signal to the first mixer (13). The fundamental frequency output is provided to a phase locked loop (20, 21, 22). The output frequency (FV) of the phase locked loop is doubled (2 FV) by a frequency multiplier (23) and provided to a phase shift circuit (24). The output of the phase shift circuit (24) is provided as the second mixing signal to the second mixer (16).

Abstract: A crystal oscillator circuit has a sleep mode of operation that reduces power consumption while maintaining oscillation to provide for a fast transition to a normal mode of operation.

Abstract: A wide frequency deviation voltage controlled crystal oscillator includes a multiple section bandpass filter containing a plurality of crystal or ceramic elements. One embodiment includes a plurality of crystals which are connected into parallel conduction paths. The crystals have resonant frequencies which are separated by small, selected intervals so that the oscillator may be adjusted to a wider range of frequencies than prior art oscillators. Alternatively, the same result may be achieved by using crystals with the same resonant frequency and connecting each crystal to a capacitor having a selected value. In another embodiment a multiple section crystal or ceramic bandpass filter is substituted for the parallel conduction paths. The principles of the invention are applicable to a number of different devices, including the ringing circuits used in color televisions to perpetuate the color bursts which appear in the blanking intervals of the incoming TV signals.

Abstract: An improved short distance, battery powered, amplitude modulated RF transmitter for transmitting encoded security data. An oscillator stage provides a control crystal and filter which are feedback coupled between the emitter and base of a transistor to oscillate at the fifth overtone of the fundamental crystal frequency. A filter tuned to the third harmonic of the overtone frequency selects the carrier frequency which is coupled via a resistive attenuator to an amplifier/filter stage, before the carrier is amplitude modulated with encoded security data. The improved transmitter circuit compensates for crystals exhibiting variations in series resistance and provides increased output power and improved frequency stability to temperature and over time. A foil antenna stage is augmented with the plates of the battery power supply to further improve performance.

Abstract: An oscillator of the feedback amplifier type is described that employs a complementary bipolar transistors pair in which the collectors have a common connection with the output terminal. The oscillator operates from a single power supply, provides near rail-to-rail voltage swings, and hence may interface directly with CMOS logic. Because of the relatively low base-emitter voltages operation with supply voltages less than one volt is possible.

Abstract: A differential mixer oscillator employing two transistors in a differential pair as the sustaining amplifier for a quartz crystal resonator at some first high frequency. The bias current of the differential pair is modulated at a second high frequency derived from some second frequency generating source, typically a second quartz crystal resonator, and the product terms are available at the collectors of the two transistors for selective filtering. The differential mixer oscillator may be employed in multiples, and with a variety of current sources, such as a Colpitts oscillator circuit.

Abstract: A multimode oscillator is disclosed which employs a single gain feedback loop for exciting at least two modes of a resonator to cause the oscillator to oscillate simultaneously at at least two frequencies. The multi-mode oscillator comprises the resonator, an amplifier to provide gain at the appropriate operating frequencies to support simultaneous oscillation at such frequencies and an equalizing network with amplitude and phase characteristics versus frequency to support the simultaneous modes of oscillation. The single loop oscillator permits separate control of the two simultaneous different frequencies of oscillation. In order to minimize thermal hysteresis, at least the active portion of the feedback loop does not include inductors. In some applications, the multimode oscillator may include one or more rejection networks to suppress unwanted oscillations. The useful outputs of the multimode oscillator are one or more of the operating frequencies, harmonics and intermodulation products.

Abstract: An improved crystal oscillator and output circuit is disclosed. The oscillator has a normal operating mode and a low-power mode. In the low-power mode, a reduced current which is sufficient to maintain oscillation is supplied to the oscillator and the output circuit is disabled. The oscillator can subsequently be returned to normal mode and the output circuit enabled. Since the oscillator is never shut completely off, the time required to resume normal mode oscillations is reduced.

Abstract: An oscillator circuit with a voltage controlled oscillator (VCO) comprises a range changing circuit that adapts the d.c. control voltage of the circuit to a control signal suitable for adjusting the VCO to the full frequency range. The voltage level for the control signal can be outside the voltage range delimited by the supply voltages for the circuit. In order to obtain a voltage supply of a sufficient voltage level the output signal of the VCO is used as the input of an a.c. to d.c. converter that provides the necessary higher supply voltage for the range changing circuit.

Abstract: This invention relates to an oscillator for overtone operations which has reduced parts count and improved performance. More specifically, a new improved Pierce type of harmonic oscillator is disclosed which eliminates the need for additional bias circuit components; which does not use an LC tank circuit and which has substantially increased gain. More specifically, the new harmonic oscillator is self biased, the input impedance is an RC circuit, an LC circuit, or a resistor. The component value of the input impedance can be chosen to selectively roll off low frequency feedback gain to produce oscillation at a desired overtone of a resonator. With a differential amplifier, the resonator can be driven with both outputs of the oscillator amplifier to effectively double the available gain and eliminate the need for an additional stage of amplification.

Abstract: A crystal oscillator circuit wherein first and second transistors are connected to form a differential pair. The second transistor functions as an inverting gain stage for the oscillator and two capacitors are provided to complete a feedback path in series with a crystal which essentially functions as an inductor. The capacitors are large enough to minimize the effect of device parasitics and small enough for monolithic implementation. The square-wave output from the circuit is completely isolated from the oscillator gain stage, thus subsequent logic gates will not have any effect on the oscillator performance and DC-coupling can be used without a need for AC-coupling capacitors. The circuit is completely monolithic, requiring only an external crystal. The circuit inherently suppresses the fundamental frequency without a need for a tank circuit or a feedback resistor and does not influence the biasing.

Abstract: A digital temperature-compensated oscillator comprises a crystal oscillator, a first memory previously storing digital temperature compensation data obtained by previously measuring the relation between the ambient temperatures and the frequency deviations of the crystal oscillator, a second memory for storing frequency offset amounts of the oscillation frequency of the crystal oscillator, a temperature sensor for outputting analog detection data relating to the ambient temperature, an A/D converter for converting the analog detection data to digital detection data, a readout circuit for reading out temperature compensation data corresponding to the digital detection data and stored in the first memory according to the digital detection data and reading out the frequency offset amount stored in the second memory according to the digital detection data, an operation circuit for effecting the following calculation by use of the readout temperature compensation data and readout frequency offset amount to derive

Abstract: In an overtone crystal oscillator comprising a crystal oscillator having a feedback loop and a resonance amplifier whose amplitude characteristic has an overshoot in the range of the resonant frequency of the resonance amplifier and which is arranged in the feedback loop of the crystal oscillator, the resonant frequency of the resonance amplifier is between the frequency of the overtone to be generated and the next lower oscillation frequency of the crystal oscillator, while signals in the frequency range of the next lower oscillation frequency(ies) in relation to signals in the frequency range of the overtone to be generated in the feedback loop, particularly in the resonance amplifier, have such a phase shift that the overtone crystal oscillator cannot oscillate at the frequencies of the next lower oscillation frequency(ies) and that it only oscillates at the frequency of the overtone to be generated.

Abstract: A cointegrated high frequency oscillator including a thin film resonator and active devices formed on the same semiconductor substrate and by a process which is compatible with formation of both the thin film resonator and the active devices. The processes utilized in formation of the thin film resonator are adapted to microelectronic processing techniques such that the steps of formation of the active devices and the thin film resonator can be intermixed to the degree necessary to allow, for example, the metallization layers to serve as elements both of the active devices and the thin film resonator.

Abstract: An ultra low noise oscillator circuit including a crystal and having two outputs. At the two outputs, the signal is correlated and the noise outside of the crystal bandwidth is decorrelated. Summing the two outputs in a hybrid circuit significantly reduces oscillator phase noise by almost 3 dB. In addition, these outputs can be used to perform a single oscillator noise test on the oscillator or crystal.

Abstract: A phase-locked loop includes an oscillator controlled by means of a switching network and a microprocessor which generates, in response to the output of a phase detector, two groups of output signals. A first group (Q1 . . . QN) is for adjusting the frequency of the oscillator in steps by selectively switching in frequency determining elements, and a second group (P1 . . . PM) for feeding a pulse duration modulator. The pulse duration modulator produces a control signal for a frequency determining minimum element of the switching network. The control signal has a duty cycle indicative of the frequency determination contribution by the minimum element.

Abstract: A reactance control circuit comprising a variable reactance circuit whose reactance is determined by the currents flowing to first and second differential transistor circuits, a differential amplifier for producing first and second currents in accordance with an input voltage, and a DC amplifier circuit for amplifying the first and second currents and supplying the amplified currents to the variable reactance circuit in order to control the currents flowing to the first and second differential transistor circuits. The DC amplifier circuit includes first and second transistors for supplying output currents to the variable reactance circuit, and a base potential control circuit for, when the first and second currents are equal to each other, supplying a predetermined low potential to the bases of the first and second transistors so that the currents flowing to the first and second transistors are both reduced.

Abstract: A Colpitts oscillator has an integrated circuit. The integrated circuit includes a transistor having an equivalent large size, a bypass capacitor connected between a collector of the transistor and a ground, a first feedback capacitor connected between a base and an emitter of the transistor, a second feedback capacitor connected between the emitter of the transistor and the ground, and an emitter follower connected to the emitter of the transistor. In a package, a stray reactance and a bonding wire are designed so as to agree with an element value and a Q value which can be used as parts of a resonator. A surface elastic wave resonator disposed outside the integrated circuit is connected between the base of the transistor and the ground. The oscillator is voltage controlled by a variable capacitance diode connected in series with the resonator.

Abstract: A temperature controlled crystal oscillator circuit comprising an amplifier (12) having a feedback path including a crystal (26) and a frequency pulling element (28), and a temperature compensating voltage generating circuit (30) coupled to the frequency pulling element (28). The voltage generating circuit (30) produces a voltage, V.sub.comp, generated in accordance with the following function:V.sub.comp =b*exp[a1(T-T.sub.R)]+b*exp[-a2*(T-T.sub.R)]+c*(T-T.sub.R)whereT.sub.R is a reference temperature in degrees KelvinT is the working temperature in degrees Kelvina1, a2, b and c are constants.

Abstract: An oscillator is provided with an internal, high gain hysteresis effect so as to offset the linear regions of the waveform and to avoid spikes upsetting the count of a reference divider controlling the oscillator. The crystal (10) and capacitor (11) are connected between the base of one (T.sub.1) and the collector of the other (T.sub.2) transistor of a long-tailed pair, signals appearing at the collector thereof being fed via emitter followers (T.sub.5, T.sub.6) to a further long-tailed pair (T.sub.7, T.sub.8) having tapped collector resistors (R.sub.1, R.sub.2). The signal appearing at the tapping point of one of the further pair (T.sub.7) is fed to the base of a transistor (T.sub.3) whose collector-emitter resistor lies in the load circuit of one of the transistors (T.sub.1) of the first long-tailed pair.

Abstract: A temperature-compensated quartz crystal oscillator has two or more temperature compensating units. The first temperature compensating unit compensates the frequency-temperature characteristics of the oscillator over its rated temperature range. The other temperature compensating units further independently compensate the frequency-temperature characteristics of the oscillator within respective specific temperature regions of the compensated frequency-temperature characteristics to obtain desired frequency-temperature characteristics for the crystal oscillator.

Abstract: An ultrasonic atomizer circuit having a plurality of unit oscillator circuits has been improved by preventing undesired interference between oscillator circuits. Each unit oscillator circuit has a transistor (Q1) with a grounded collector, a piezo-electric vibrator (TD) coupled across the collector and the base of the transistor (Q1), a capacitor (C3) coupled across the emitter and the base of the transistor (Q1), and a capacitor (C1) coupled across the emitter and the collector of the transistor (Q1). An additional capacitor (C7) is provided between the base of the transistor (Q1) and the junction point of one end of the vibrator (TD) and the capacitor (C3), so that one end of said capacitor (C3) is separated from the base of the transistor for DC current.

Abstract: A single pin oscillator which consists of first and second transistors (17, 18) whose collectors are connected, via respective collector resistances (19, 20), to the positive pole of a DC source U.sub.V and whose emitters are connected to the negative pole thereof via respective emitter resistances (21, 22). The collector of each transistor is connected to the base of the other transistor. A quartz crystal (12) or a series resonant circuit is connected to the emitter of one transistor (17) and parallel to the corresponding emitter resistance (21). A driver circuit (23) is provided for an oscillator voltage which can be coupled out to an external low-ohmic, highly capacitive load connected to the emitter of the other transistor (18) and parallel to the corresponding emitter resistance (22).

Abstract: A voltage variable capacitor (VVC) having two terminals in a variable frequency crystal oscillator integrated into a common substrate with the oscillator circuitry and isolated therefrom. The VVC is constructed using the same processing steps as the oscillator circuitry and achieves low series resistance and wide capacitance variation by utilizing a substrate or epitaxial layer (body) having a well with a diffused region therein. The region, of the same conductivity type as the well and a first one of the two terminals, forms a rectangular ring in the well. Over the region and insulated therefrom, a conductive layer is deposited to provide a second one of the two terminals. Both terminals are electrically isolated from the body.

Abstract: A crystal oscillator including a crystal element designed to oscillate at a given frequency when subjected to an exciting voltage, and mounted parallel to and on a base through at least a wad made of at least a thin wound wire. Advantageously, the wire is randomly wound and is electrically conductive. The wad is elongated and is disposed parallel to said crystal and to said base.

Abstract: A crystal oscillator circuit for use with overtone crystals restricts its resonant frequency to either fundamental or overtone frequencies. An inverting amplifier, which provides 180 degrees of phase shift by inverting an input signal, includes components which effectively provide another 180 degree phase shift at a particular frequency by adding a time delay. The 180 degree phase shift by a signal inverting amplifier, with the included 180 degree phase shift provided by the time delay comprises an oscillator by the addition of a crystal with a resonant frequency equal to the particular frequency determined by the time delay. Suppression of unwanted oscillation frequencies is accomplished by adjusting a current source, which changes time delay, without using inductors or other reactive components.

Abstract: A first transistor is connected in grounded-collector-emitter-follower configuration to generate a high enough negative resistance to overcome the oscillating resistance of the crystal resonator connected to the base electrode. A second transistor connected in grounded-base configuration serves as a buffer and impedance transformer between the low impedance output of the first transistor and the high impedance of a load. An inductor connected between the resonator and the first transistor input and a variable capacitance approximating the shunt capacitance of the resonator connected across the first transitor input form an impedance inverter which absorbs the resonator shunt capacitance and converts the effect of the resonator to a parallel tuned circuit that can be broadly tuned.

Abstract: An oscillator including a CMOS inverter, a feedback reactance connected between the input and output terminals of the CMOS inverter and a CMOS transfer gate connected as a feedback resistor between the input and output terminals of the CMOS inverter, a power source terminal section to which an external voltage is applied, and a power control unit for converting the external voltage to a first internal voltage which is supplied as a power source voltage to the CMOS inverter. The power control unit converts the external voltage to a second internal voltage independently from the first internal voltage and supplies the second internal voltage as a gate control voltage to the CMOS transfer gate.

Abstract: A piezo-oscillator includes a semiconductor element having at least an oscillating circuit. A piezo-vibrator having leads extending therefrom is connected to the semiconductor element by a plurality of lead terminals. The semiconductor, vibrator and lead terminals are contained within a unitary resin package.

Abstract: A voltage controlled oscillator free from free-run oscillating frequency adjustment is disclosed. This oscillator includes an amplifier having a positive feedback loop, a resonator connected to the output of the amplifier, and a variable reactance circuit connected to the output of the amplifier. The reactance circuit presents a reactance value variable by a control voltage to control an oscillation frequency of the oscillator. There is a further provided a low-pass filter which is connected in cascade to the variable reactance circuit. A high-pass filter is preferably inserted in the positive feedback loop.

Abstract: A temperature-compensated crystal oscillator utilizing a fundamental frequency crystal with an input RC network to bias an input transistor. Temperature compensation for the oscillator is achieved by the use of a series diode in the emitter circuit of the input transistor. As the temperature changes, the emitter-to-base voltage varies and causes the emitter current to vary in the opposite direction. The voltage across the series diode tracks with the emitter-to-base voltage in the same direction. With these occurrences, the emitter-to-collector voltage is controlled and stabilized over a range of temperature changes. The parallel RC circuit which couples the input transistor to the output drive transistor provides the necessary base current and input impedance for the output trnasistor to permit saturation of and wave shaping by the output drive transistor.

Abstract: A voltage-controlled oscillator in which a phase shifter is connected to a ceramic piezoelectric resonator. The phase shifter has a first circuit branch containing an amplifier. A second circuit branch is connected in parallel with the first circuit branch and includes a low-pass filter connected in series with a controllable amplifier and switch. The output of the controllable amplifier is applied to a first input of the switch, and a source of reference potential is connected to a second input of that switch. The switch has an output connected to a summing element at a first input of the summing element. A second input of that summing element is connected to the amplifier in the first circuit branch. The output of the summing element is fed back to the ceramic piezoelectric resonator.

Abstract: A circuit is shown for representing the internal temperature of a crystal, through a combination of certain harmonic frequencies excited in that crystal. By forming a signal which is equal to nF.sub.A -F.sub.B, i.e., n times a lower harmonic frequency minus F.sub.B, an nth harmonic frequency, or F.sub.A -1/n F.sub.B, e.g., it is possible to have a signal which is near linearly dependent upon temperature which can be used in representing same. This composite signal is also seen to be highly sensitive to temperature changes yielding an improved thermometric system as compared to conventional systems.

Abstract: An oscillator circuit comprising a feedback amplifier circuit having a power supply terminal, a resonant circuit comprising a crystal, and a differential amplifier which is coupled to a bias current source which is switchable stepwise by means of a level detector for the stepped excitation of the resonant circuit from a predetermined potential at the power supply terminal. When switching on the power supply voltage, the level detector insures that the resonance of the oscillator circuit is achieved in a defined and a reproducible way.

Abstract: An oscillator for producing an oscillating signal with reduced harmonics includes an oscillator stage coupled to an output stage having a relatively fast switching speed yet producing an oscillating signal having relatively slow rise and fall times so that the harmonics output by the oscillator are reduced. In one embodiment, the oscillator includes an output stage having low power Schottky circuitry, and in a second embodiment, the output stage includes a capacitor connected across the output stage of the oscillator to increase the rise and fall times of the oscillator.

Abstract: A short distance, battery powered, amplitude modulated, crystal controlled RF transmitter for transmitting encoded security information. In its preferred embodiments, the transmitter comprises a novel fifth overtone crystal oscillator which self-produces a carrier frequency at the third harmonic of the fifth overtone of the crystal's fundamental frequency, which carrier frequency is coupled by a series resonant trap, or a pi network, tuned to the carrier frequency to an amplifier stage where the carrier is amplitude modulated via pulse position encoded binary security data. In an alternative embodiment, the transmitter comprises matched crystal oscillator, tripler and amplifier stages. Also disclosed is an antenna including a battery clip contact.

Abstract: A simple and inexpensive crystal oscillator is provided which employs negative voltage gain, single pole response amplifiers. The amplifiers may include such configurations as gate inverters, operational amplifiers and conventional bipolar transistor amplifiers, all of which operate at a frequency which is on the roll-off portion of their gain versus frequency curve. Several amplifier feedback circuit variations are employed to set desired bias levels and to allow the oscillator to operate at the crystal's fundamental frequency or at an overtone of the fundamental frequency. The oscillator is made less expensive than comparable oscillators by employing relatively low frequency amplifiers and operating them at roll-off, at frequencies beyond which they are customarily used. Simplicity is provided because operation at roll-off eliminates components ordinarily required in similar circuits to provide sufficient phase-shift in the feedback circuitry for oscillation to occur.

Abstract: A crystal-controlled oscillator exhibiting reduced levels of crystal-induced low frequency noise, vibration sensitivity and circuit temperature rise includes an amplifier or oscillator sustaining stage which is secured to a heat sink. A plurality of crystals connected with each other in a preselected electrical configuration are secured to a vibration dampening structure which extends from the heat sink, and the plurality of individual crystals are connected with the oscillator sustaining stage via a preselected wavelength section of coaxial cable. The coaxial cable wavelength may be varied to provide that the plurality of individual crystals operate at either series or parallel resonance.

Abstract: A crystal-controlled oscillator operable at a direct UHF frequency includes an amplifier having a feedback circuit formed from an SC-cut crystal and an impedance network. The impedance network provides an impedance load for the cyrstal, and the values of the individual components forming the impedance network are selected to provide an overall inductive load for the SC-cut crystal. Inductively loading the cyrstal permits the crystal to oscillate at the C mode or UHF frequency mode, and prevents unwanted crystal oscillation at the B mode or VHF mode.

Abstract: A monolithically integrable amplitude-controllable oscillator amplifier circuit includes a differential amplifier. The bases of first, second and third transistors are acted upon by a direct voltage. A first capacitor connects the base of the second transistor to a reference potential. A frequency-determining circuit element is connected to the base of a first transistor, the collector of the second transistor and the oscillator amplifier. The collector of the first transistor is connected directly to the emitter of the third transistor forming a cascode circuit. The collector of the third transistor is connected to a first potential. The collector of the second transistor forms an amplifier output. A first resistor is connected between the collector of the second transistor and a second potential.

Abstract: A temperature-compensated piezoelectric oscillator of high-spectral purity, capable of being controlled in frequency, consists of a compensation circuit, a processing circuit, a phase-shifting circuit, containing the piezoelectric resonator, and an oscillating circuit. To obtain high spectral purity, it is proposed to use a low-pass filter, placed between the compensation circuit and one of the inputs of the processing circuits, to process the signal coming from the compensation circuit. This filter eliminates the influence of the temperature noise coming from the compensation circuit. The invention can be applied to controllable frequency, temperature compensated piezoelectric oscillators where high spectral purity is sought.

Abstract: A crystal oscillator circuit having an accurate duty cycle at very high frequency is provided. An oscillator stage is provided which receives regenerative feedback from an inverter to sustain oscillation. The oscillator stage provides an AC output signal having a first average DC value determined by the regenerative feedback. The AC signal is coupled to a clipping circuit which symmetrically clips the AC signal about a predetermined second average DC level at first and second predetermined voltage levels. The inverter receives the clipped signal and provides an oscillating clock signal with an accurate duty cycle in response thereto.

Abstract: An oscillator with noise rejection which may be used in a gate array in a semiconductor chip including a first amplifier circuit, a circuit, for connecting an external feedback element (crystal) across the input and inverting output of the first amplifier circuit for generating and amplifying a sine wave, and a circuit connected to the inverting output of the first amplifier circuit for generating a square wave with the duty cycle thereof being proportional to the difference between the center of the voltage swing of the amplified sine wave and a reference voltage. In a preferred embodiment, the first amplifier circuit and the generating circuit each include a current switch. A voltage reference network is provided to set the reference voltage for the current switch in the generating circuit to the center of the voltage swing of the sine wave applied to that current switch. This results in a 50% duty cycle square wave for the output signal.

Abstract: A crystal controlled oscillator in which changes in damping are compensated and a method for decoupling the output signal of such an oscillator from damping changes. The damping decoupled oscillator includes a quartz crystal (10), which produces a periodic signal, connected in series with a variable gain amplifier (18) and a variable phase shift circuit (22). Feedback from the output of the variable phase shift circuit is provided to sustain oscillation of the crystal. Unity gain in the loop is maintained by adjusting the gain of the variable gain amplifier in accordance with the DC value of the output signal, provided by a precision rectifier (34). As the DC value of the output signal changes due to changes in damping or energy loss of the crystal, an absolute value circuit (38) responds by providing a phase control signal for adjusting the phase of the periodic signal to compensate for changes in damping.

Abstract: The frequency of a voltage controlled crystal oscillator is conventional pulled by means of a varicap diode forming the load capacitance of the oscillator crystal. In order to realize a wider range of frequency pulling, the load capacitance 44 is alternately switched on and off in a known manner. According to the invention a band-switch diode 46 is utilized as a switch element, the hole-storage time of this diode being as long as or longer than the oscillator cycle. By applying a low-frequency control voltage to the diode it is rendered self-switching within the oscillator cycle, so that proportional frequency tuning is achieved.

Abstract: A variable frequency circuit for generating a frequency output variable in response to a control signal. The variable frequency circuit includes a ceramic resonator, an exciting amplifier for exciting an oscillation in the ceramic resonator, a first current supplying circuit for supplying a driving current to the exciting amplifier, a variable reactance circuit connected in parallel to the ceramic resonator, the variable reactance circuit operating as an equivalent reactance, a second current supplying circuit responsive to the control signal for supplying a variable driving current to the variable reactance circuit, and a coupling circuit for coupling the first current supplying circuit and the second current supplying circuit together for controlling the driving current of the first current supplying circuit in response to the variable driving current of the second current supplying circuit.

Abstract: The resonant frequency of a quartz-crystal microwave oscillator is the fundamental frequency in the partial mode of the crystal and makes it possible to maintain the loaded Q of the resonator at a high value. This microwave oscillator is provided with two amplifying stages and has a signal-to-noise ratio of the order of 160 dB.

Abstract: A channel switching oscillator circuit (230) in which the oscillator frequency is selected from one of a predetermined number of frequencies by switching into the oscillator circuit (230) one of a plurality of tank circuits (L4, L5, L6). The tank circuit (L4, L5, L6) is resonant with one of a plurality of crystals (Y2, Y3, Y4) in the oscillator (230) to generate a carrier signal at the predetermined frequency. The crystals (Y2, Y3, Y4) remain in the oscillator circuit (230) with no switching thereof as the frequencies at which the crystals (Y2, Y3, Y4) oscillate are sufficiently far apart, coupled with the high Q of the tank circuit (L4, L5, L6), that only one of the crystals (Y2, Y3, Y4) is resonant with each tank circuit (L4, L5, L6).

Abstract: A voltage controlled oscillator having a first feedback path and a second feedback path. The first feedback path may include a phase shift unit (13) as necessary to compensate for an inherent phase shift provided by the resonant circuit (11) used therewith. The second feedback path includes a steering network (17) that responds to an external control signal to cause the output signal to be selectively in either of two phase relations with respect to the incoming signal. The control signal can also control the magnitude of the output signal. By control of the phase relationship and the magnitude, the steering network (17) can effectively control the output frequency of the resonant circuit (11).

Abstract: A voltage-controlled circuit includes a control voltage source for providing a variable control voltage, a first current source for providing a first current whose magnitude is changed with the variation of the control voltage, a first potential source for providing a first potential which depends on the magnitude of the first current, a second current source for providing a second current, a second potential source for providing a second potential which depends on the magnitude of the second current, and a differential amplifier circuit which is formed of a first transistor having a base coupled to the first potential source and a second transistor having a base coupled to the second potential source. An input signal is supplied to the emitter circuit of the first and second transistors, and an output signal is delivered from the collector circuit of the first or second transitor. The output/input characteristic of the differential amplifier circuit is changed by the control voltage.