Abstract: Radio terminal equipment is provided with an oscillator connected to a receiving circuit, a DPLL 16 for detecting and correcting the phase difference between the received frequency and the oscillation frequency of the oscillator, a switch for connecting a capacitor to or disconnecting from the oscillator, and control means 17 for effecting ON-OFF control of the switch based on the output signal from the DPLL 16.

Abstract: A method and apparatus for synthesizing high-frequency signals is disclosed that overcomes integration problem associated with prior implementations while meeting demanding phase noise and other impurity requirements. In one embodiment, a phase-locked loop (PLL) frequency synthesizer is disclosed having a voltage controlled oscillator (VCO) with a variable capacitance that includes a discretely variable capacitance in conjunction with a continuously variable capacitance. The discretely variable capacitance may provide coarse tuning adjustment of the variable capacitance, and the continuously variable capacitance may provide a fine tuning adjustment of the variable capacitance.

Abstract: A method and apparatus for synthesizing high-frequency signals is disclosed that overcomes integration problem associated with prior implementations while meeting demanding phase noise and other impurity requirements. In one embodiment, a phase-locked loop (PLL) frequency synthesizer is disclosed having a voltage controlled oscillator (VCO) with a variable capacitance that includes a discretely variable capacitance in conjunction with a continuously variable capacitance. The discretely variable capacitance may provide coarse tuning adjustment of the variable capacitance, and the continuously variable capacitance may provide a fine tuning adjustment of the variable capacitance. In a more general terms, a frequency synthesizer is disclosed having a first variable and a second capacitance circuits and frequency control circuitry to coarsely tune the output frequency by adjusting the first control signal and to finely tune the output frequency by adjusting the second control signal.

Abstract: An oscillator circuit (100) provides improved noise immunity by utilizing a differential common base configuration. The oscillator includes a differential transistor pair (102, 104) having common bases (110) coupled through an AC ground (108) and emitters coupled through a differential common mode point (120). First and second resonant tank circuits are each referenced to the differential common mode point (120) for generating a differential output (OUT, OUTX).

Abstract: In the method and circuit for creating a modulated signal, one input signal of a phase comparator (509) of a phase-locked frequency synthesizer is an offset frequency (f.sub.2), which is created from an adjustable oscillator's (511) output signal (f.sub.TX) by mixing it with a mixer frequency (f.sub.1) and filtering the obtained result in a low pass filter (508). The other input signal is a fixed reference frequency (f.sub.r). The adjustable oscillator (511) is controlled with a control signal (V.sub.CMOD), which contains a component resulting from the phase difference of said input signals (f.sub.r, f.sub.2). Modulation is created in the output signal (f.sub.TX) of the loop by adding a frequency or phase change to at least one of the input signals (f.sub.r, f.sub.2) or their derivatives, advantageously with pulse delay technology.

Abstract: In a receiver of the present invention, a local oscillator frequency, used as a basis for a reception unit to demodulate a received signal, is generated by a local oscillator based on a reference frequency, which is generated by a voltage-controlled oscillator whose oscillation frequency is adjusted by a control voltage applied thereto. The control voltage is prescribed by a decoding unit which monitors a reception electric field intensity (RSSi) or an error rate in the reception unit. The control voltage is adjusted in a manner to increase the reception electric field intensity (RSSi) or reduce the error rate. When the local oscillator frequency experiences a large deviation and the signal cannot be received with good reception sensitivity, the decoding unit generates a control voltage in a manner so as to eliminate the deviation and applies the generated control voltage to the voltage-controlled oscillator for automatically adjusting the local oscillator frequency to a level having a reduced deviation.

Abstract: A high frequency television signal receiving apparatus providing excellent linear detection of output characteristics by improving the phase characteristic of the picture synchronous detector. A variable capacitive element is equivalently connected in parallel to a reference solid-state oscillation element. The reference solid-state oscillation element controls the frequency of a local oscillation device including a PLL circuit for feeding a local oscillation signal to a mixer for converting a high frequency signal into an intermediate frequency signal. A first low pass filter is connected between a phase comparator for detecting a phase difference of the intermediate frequency signal and the output of a detection oscillator for generating a detection oscillation signal with a specific phase difference. A second low pass filter having a larger time constant than the first low pass filter is connected to the variable capacitive element.

Abstract: An oscillator (100) includes a resonator (218) having a mirco-strip (217). The micro-strip (217) couples an inductive component (221) to a capacitive portion (219). To tune the oscillator (100), a number of cuts are made on the pad (221) in order to restrict the signal flow. The width of these cuts determine the degree of restriction posed on the signal flow. This controllable restriction of the signal flow provides the circuit (100) with enhanced tunability.

Abstract: A voltage controlled tunable resonant circuit (100) has at least two resonant frequency ranges and reduced self modulation, and includes a resonant element (120), a variable reactance element (130), and a first voltage variable capacitor (VVC) (150). The variable reactance element (130) is coupled to the resonant element (120). The VVC (150) has two fixed capacitance values corresponding to two fixed capacitance bias voltage ranges, and is coupled to the resonant element (120) and the variable reactance element (130). The first VVC (150) is controlled by a first DC bias voltage (190) selected to be within one of the two fixed capacitance bias voltage ranges to establish one of the two resonant frequency ranges over which the voltage controlled tunable resonant circuit (100) is tuned by variation of the variable reactance element (130).

Abstract: An oscillator provided with an oscillation circuit provided with two oscillation transistors comprising a differential pair and a resonance circuit connected in common to the bases of the oscillation transistors. The bases of the oscillation transistors are short-circuited by a coil, a center tap coil is connected in parallel to the resonance circuit, and variable capacitive diodes in the resonance circuit are driven by a coil connected to a mixing circuit. Due to this, it is possible to prevent the occurrence of low frequency noise, possible to realize a completely balanced operation, possible to avoid the oscillation carrier flowing into the power source and ground, and possible to reduce the noise in a television picture.

Abstract: An oscillator comprising an amplifier device, a capacitive divider bridge whose terminals are connected between a control electrode of the device and a reference voltage, the intermediate junction point of this bridge being connected to a principal electrode of the device, and also comprising, in parallel between the control electrode and the reference voltage, a tuning circuit having parallel branches: a first branch with an inductance in series with a variable capacitance, and, a second branch equivalent to a variable capacitance. The tuning circuit has a third branch constituted by a capacitance in parallel with the first branch, while a series inductance whose value is smaller than that of the tuning inductance is arranged between the junction point connecting the two latter branches and the junction point connecting the control electrode of the device to the second branch and to the divider bridge.

Abstract: In a radio transceiver (11) including a voltage controlled oscillator (VCO) (24) having an output for coupling to a switchable load (32, 30), a switch (42) couples a compensating load (44) to the output of the VCO when the switchable load is in an off state. The compensating load has an impedance that compensates for the decoupling of the load impedance from the output of the VCO, thus avoiding frequency pull problems. In a further aspect of the invention a voltage variable capacitor (100) is used as the switch.

Abstract: Frequency control in a miniature receiver is effected by a synthesizer that is operated briefly to provide a tuning voltage to a voltage controlled local oscillator. A capacitor is shunted across the output of the synthesizer and is charged to the level of the tuning voltage. After the capacitor is charged, the synthesizer is deenergized and the diminishing voltage provided to the oscillator by the discharging capacitor is correspondingly supplemented by an AFC voltage that tracks drift of the received signal in the IF passband. The deenergizing of the synthesizer eliminates synthesizer noise and reduces the receiver's power consumption.

Abstract: In an electronic tuning circuit for AM receiver including a radio-frequency tuning circuit and local oscillator circuit each using a variable capacitance diode, the local oscillator circuit comprises an oscillation coil; a padding capacitor connected in series with the oscillation coil; a first variable capacitance diode connected at one end in series with the oscillation coil; a first and a second fixed capacitor connected at one end in series with each other; and a second variable capacitance diode connected in parallel with the second fixed capacitor. The second fixed capacitor has its other end connected to a connection point between the padding capacitor and the first variable capacitance diode. The first fixed capacitor has its other end connected to the connection point between the oscillation coil and one end of the first variable capacitance diode. A tuning voltage is applied to the first and second variable capacitance diodes, thereby reducing tracking error over the entire receiving frequency band.

Abstract: A tuning arrangement including a mixer stage, a tunable RF-circuit coupled to an input of said mixer stage, an oscillator circuit, coupled to another input of said mixer stage, having a tunable resonant circuit and, for both circuits, a common tuning to mutually different resonant frequencies, of which at least the circuit having the higher resonant frequency includes, a parallel circuit of, on the one hand, a circuit inductance and, on the other hand, a series arrangement of a tuning capacitor and a padding capacitor. For an acceptable tracking between the resonant frequencies of the two circuits, more specifically in the lower frequency portion of the tuning range, the padding capacitor is shunted by a coil which considerably reduces the effect of the capacitance of the padding capacitor at least in the lower frequency portion of the tuning range.

Abstract: The AFC gain of the local oscillator of an AM stereophonic decoder is linearized by the use of difference channel (L-R) information for controlling the capacitance of two varactor-type devices coupled across and in series with the oscillator inductance coil. The improvement helps to prevent "falsing" of the pilot tone indicator and the mono/stereo mode circuitry, particularly at the ends of the tuning range of a manually tuned receiver.

Abstract: An oscillator circuit suitable for use in a local oscillator of a tuner of a television receiver set. A feedback circuit comprised of a feedback capacitor (17) is connected between a junction of a tuning diode (10) and a correcting capacitor (11) connected in series therewith and the emitter of an oscillation transistor (1). Oscillation voltage developing across the correcting capacitor is fedback to the emitter of the oscillation transistor through the feedback capacitor. When the tuning diode is conditioned to have a large capacitance value, a large oscillation voltage is fedback to the transistor through the feedback capacitor whereas when the tuning diode is conditioned to have a small capacitance value, a small oscillation voltage is fedback to the transistor through the feedback capacitor. The oscillator circuit continues to oscillate stably over a wide frequency range whenever the tuning diode changes from the small capacitance value to the large capacitance value or vice versa.

Abstract: A channel selection voltage generator comprises a tuning voltage generator circuit having a capacitor for supplying a tuning voltage to an electronic tuner, a first constant current source for constantly discharging the capacitor at a first constant current and a second constant current source adapted to be rendered selectively in an operative state and in an inoperative state for selectively charging the capacitor at a second constant current which is higher than the first constant current, a frequency discrimination circuit for producing a discrimination signal representative of the amount of frequency deviation when a tuning voltage deviates from a receiving frequency, a buffer circuit for producing a binary "1" level signal when the discrimination signal is higher than a predetermined value and producing a binary "0" level signal when the discrimination signal is lower than the predetermined value, and a control circuit for causing the second constant current source to assume the inoperative state when th