Abstract: Methods, apparatuses, and computer-readable medium for DPD are provided. An example method may include receiving, from a base station, an uplink grant associated with one or more resources. The example method may further include transmitting, to the UE via the one or more resources, a DPD training signal at a first port of a plurality of ports. The example method may further include receiving, at a second port of the plurality of ports, the DPD training signal.

Abstract: A scanning method performed by a station (STA) in a wireless LAN system is provided. The method comprises: transmitting a probe request frame; and receiving a short probe response frame from an access point (AP) as a response to the probe request frame. The short probe response frame includes service set ID (SSID) information or compressed SSID information of the AP.

Abstract: A method and system for joining a Wi-Fi network with a mobile device based on historical device behavior includes detecting, using a mobile device, a new Wi-Fi network connection is available for connection by the mobile device. The method and system includes determining that the new connection meets a first connection threshold based on first connection factors. The method and system further includes analyzing historical data regarding acceptance of Wi-Fi network connections for the device. The analysis of the historical data is used to determine a pattern for accepting a connection. The method and system includes determining when to accept the new Wi-Fi network connection based on the new connection meeting the first connection threshold based on the first connection factors, and the second connection threshold based on the historical data.

Abstract: A terminal includes a first baseband processor, a second baseband processor, a first radio frequency chip, a second radio frequency chip, a first antenna, a second antenna, a third antenna, and a fourth antenna. The first baseband processor is coupled to the first antenna and the second antenna using the first radio frequency chip. The first radio frequency chip is coupled to the first antenna to form a first channel, and is coupled to the second antenna to form a second channel. The second baseband processor is coupled to the third antenna and the fourth antenna using the second radio frequency chip. The second radio frequency chip is coupled to the third antenna to form a third channel, and is coupled to the fourth antenna to form a fourth channel.

Abstract: A multi-band amplifier may include: a first amplifying unit connected to a first antenna stage; a second amplifying unit connected to a second antenna stage; and a switching control unit generating a control signal to activate at least one of the first and second amplifying units depending on a plurality of control voltages, wherein the first amplifying unit amplifies the signal within the first frequency band or provides the signal within the first frequency band to the first antenna stage by performing a switching operation depending on the control signal, and the second amplifying unit amplifies the signal within the second frequency band or provides the signal within the second frequency band to the second antenna stage by performing a switching operation depending on the control signal.

Abstract: In one embodiment, an amplifier system has a tap, a delay filter, a linearized amplifier, and a hybrid combiner. The tapped portion of an input signal is amplified by the amplifier, the untapped portion of the input signal is delayed by the delay filter, and the combiner combines the resulting amplified, tapped portion and the delayed, untapped portion to generate an amplified output signal. By re-combining the delayed, untapped portion of the input signal with the amplified, tapped portion, the power of the untapped portion is not lost, and the amplifier does not have to compensate for all of the distortion that would otherwise be associated with the total output power level. Such an amplifier system is applicable, for example, in upgrading an existing GSM cell site to support both GSM communications as well as UMTS communications without degrading GSM operations.

Abstract: One embodiment of the present invention relates to a combined mixer filter circuit. The circuit includes a sampler, a plurality of filter branches, and a coefficient generator. The sampler is configured to provide a sampled signal by sampling a received signal at a specified rate. The plurality of filter branches has selectable filter coefficients. The plurality of filter branches are configured to receive the sampled signal and generate a mixed and filtered output signal without a separate mixer component. The coefficient generator is coupled to the plurality of filter branches. The coefficient generator is configured to assign filter coefficient values to the selectable filter coefficients to yield a selected mixing function for the mixed filtered output signal.

Abstract: A wireless communications device may include a portable housing and a temperature-compensated clock circuit carried by the portable housing. The device may further include a wireless receiver carried by the portable housing for receiving timing signals, when available, from a wireless network, and a satellite positioning clock circuit carried by the portable housing. A clock correction circuit may be carried by the portable housing for correcting the temperature-compensated clock circuit based upon timing signals from the wireless network when available, and storing historical correction values for corresponding temperatures. The clock correction circuit may also correct the temperature-compensated clock circuit based upon the stored historical correction values when timing signals are unavailable from the wireless network, and correct the satellite positioning clock based upon the temperature-compensated clock circuit.

Abstract: A mobile device having at least two antennas can circumvent transmission problems caused by a user's grasp of the device. A sensor unit is disposed at a specific location of a device body and creates a sensor signal by detecting the contact or proximity of a particular object such a user's hand. When receiving the sensor signal, a control unit selects one of the antennas depending on the sensor signal and establishes a communication path based on the selected antenna. The selected antenna involved in the communication path is typically relatively free from degradation in transmission caused by a user's grasp of the mobile device. The radiation property of the mobile device, which may be degraded due to a user's grasp, can exhibit relatively little or no degradation as compared to the typical degradation in performance when the mobile device is being grasped.

Abstract: A signal processing device includes a device package, processing circuitry and biasing circuitry. The processing circuitry is packaged in the device package and is operative to receive one or more Radio Frequency (RF) input signals from one or more antenna elements via one or more pre-amplifiers that are separate from the device, and to process the RF input signals so as to produce an RF output signal. The biasing circuitry is packaged in the device package and is operative to produce one or more biasing signals for biasing the pre-amplifiers.

Abstract: One embodiment relates to a circuit for efficient wireless communication. The circuit includes an antenna interface module adapted to receive multiple frequency components via an antenna. Multiple reception paths stem from the antenna interface module, where different reception paths are associated with different frequency components. The circuit also includes multiple filter elements having inputs respectively coupled to the multiple reception paths. At least two of the filter elements cooperatively form a differential output signal based on their respective frequency components. Other methods and systems are also disclosed.

Abstract: A closed loop power output calibration system for variable power output wireless devices. The wireless device includes a wireless transceiver having a transmit core coupled to a discrete power amplifier. Power detection circuitry formed in the wireless transceiver provides a detected power level of the power amplifier, and a reference power level, both of which are converted to digital signals using existing I and Q signal analog to digital converters in the receiver core. The digital signals are processed to cancel power distortion and temperature effects to provide a resulting power feedback signal. Corrective control signals are generated in response to the power feedback signal relative to a desired power output level. The gain in the transmit core is then adjusted in response to the corrective control signals such that the power amplifier outputs the target output power level.

Abstract: A mode-switching LNA generally includes an input unit, an output unit and a bias voltage generator. The input unit amplifies an input signal to generate an amplified signal. The output unit receives the amplified signal from the input unit and operates either in an oscillation mode or in an amplification mode in response to a control signal to generate an output signal having a center frequency equal to a target frequency. The control signal indicates whether the center frequency of the output signal is the same as the target frequency. The bias voltage generator provides an input bias voltage to the input unit in response to the control signal, where the input bias voltage includes a first bias voltage in the amplification mode and a second bias voltage in the oscillation mode.

Abstract: A method, mobile electronic device and system for synchronizing hand-off of a voice media session between a WAN/cellular network and a WLAN network. When a hand-off occurs, the connection with both networks is temporarily maintained and the voice data on both connections compared to determine differences in the delays experienced over both connections. The timing of one or both voice streams is adjusted to synchronize the voice streams, and then the handoff is completed.

Abstract: Circuits, architectures, a system and methods for providing on-chip gain calibration. The circuit generally includes a receiver comprising (i) a resistor on a semiconductor substrate, the resistor configured to provide a signal having a noise component that varies with temperature, and (ii) an amplifier circuit on the semiconductor substrate coupled to the resistor, the amplifier circuit configured to receive the signal and provide a second signal having an amplitude greater than the first signal. The architectures and/or systems generally include those that embody one or more of the inventive concepts disclosed herein. The method generally includes (i) providing a noise signal from a resistor to an amplifier, the resistor being on a common semiconductor substrate with the amplifier, (ii) determining a resistance value of the resistor, (iii) determining an impedance at an input of the amplifier, and (iv) determining a gain of the amplifier.

Abstract: A wireless communications device may include a portable housing and a temperature-compensated clock circuit carried by the portable housing. The device may further include a wireless receiver carried by the portable housing for receiving timing signals, when available, from a wireless network, and a satellite positioning clock circuit carried by the portable housing. A clock correction circuit may be carried by the portable housing for correcting the temperature-compensated clock circuit based upon timing signals from the wireless network when available, and storing historical correction values for corresponding temperatures. The clock correction circuit may also correct the temperature-compensated clock circuit based upon the stored historical correction values when timing signals are unavailable from the wireless network, and correct the satellite positioning clock based upon the temperature-compensated clock circuit.

Abstract: An electric device for receiving a radio frequency (RF) signal is provided. The electric device includes an antenna, a first power amplifier, a battery, a second filter and a second power amplifier. The antenna is used for receiving and outputting a RF signal. The first power amplifier is used for receiving the RF signal, amplifying the RF signal and outputting the RF enhanced by the first power amplifier and a feedback signal. The battery is used for providing a working voltage to the first power amplifier, and receiving and outputting the feedback signal. The second filter is used for receiving the working voltage provided by the battery and the feedback signal, filtering the feedback signal and outputting the working voltage. The second power amplifier is used for receiving the working voltage.

Abstract: According to one embodiment, a method involves determining whether a wireless connection between a first access point and a wireless station has failed. If so, a partial scanning process is conducted only on a subset of communication channels over which data is transmitted by access points neighboring the first access point. The subset of communication channels, inclusive of zero, is determined by analysis of a scanning history database.

Abstract: A radio front end utilizes at least one band pass filter to pass only the appropriate frequency band. Once the desired frequency band has been isolated it is converted to a digital format in an analog to digital converter and a digital signal processing device interprets the signal.

Abstract: A communications transceiver incorporating diversity architecture for utilization with a wireless communications network and having improved receiver sensitivity is disclosed. In a first embodiment of the invention, the communications transceiver comprises a pair of antennas connected to a pair of amplifiers and a selector connected between the amplifiers and the intermediate frequency stage of the transceiver for providing selective operation of the communications transceiver with either antenna of the pair of antennas. In a second embodiment of the invention, the communications transceiver comprises a pair of antennas, a pair of amplifiers and a selector disposed between the first amplifier and the intermediate frequency stage of the transceiver and between the second antenna and the second amplifier for providing selective operation of the communications transceiver with either of the antennas.

Abstract: A wireless receiver (100) is provided, comprising: a non-coherent signal detector (130) configured to receive an incoming signal and perform a non-coherent signal analysis in response to a first control signal; a coherent signal detector (140) configured to receive the incoming signal and perform a coherent signal analysis to extract coherently-encoded data from the incoming signal in response to a second control signal; and a receiver circuit (160) configured to process the coherently-encoded data. The non-coherently-encoded data provides an indication as to whether the incoming signal includes the coherently-encoded data, and the coherent signal detector is further configured to enter in a low power sleep state in response to a third control signal.

Abstract: An exemplary embodiment of the present invention described and shown in the specification and drawings is a transceiver with a receiver, a transmitter, a local oscillator (LO) generator, a controller, and a self-testing unit. All of these components can be packaged for integration into a single IC including components such as filters and inductors. The controller for adaptive programming and calibration of the receiver, transmitter and LO generator. The self-testing unit generates is used to determine the gain, frequency characteristics, selectivity, noise floor, and distortion behavior of the receiver, transmitter and LO generator. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.

Abstract: The subject of the present invention is a frequency and phase modulation remote control receiver for a geostationary satellite which is lighter and less expensive than the customary receivers, while not degrading the passband of the telecommunication equipment for its payload, and it is characterized in that it comprises a heterodyne amplifier analog input and filtering circuit (28) followed by a digital processing circuit (49) configurable as an FM demodulation device or as a PM demodulation device, the analog input circuit being common to both modes of demodulation.

Abstract: A system and method for transmitting a signal in a communication system are provided. In the signal transmitting method, a multi-FA signal is generated by combining single FA signals to be transmitted by N FAs. An operation mode is determined for N MMPAs according to a used FA strategy and adjustment of amplification characteristics of the N MMPAs is controlled according to the operation mode. The power of the multi-FA signal is divided by N, the N divided signals are amplified according to the adjusted amplification characteristics, and the power of the amplified N signals is combined.

Abstract: In a SPDT switch, a resistor for leak path is connected between a terminal for antenna and a reference potential. The resistor for leak path allows charge capacitances accumulated in electrostatic capacitor elements provided as DC cut capacitors connected to transmission signal terminals and reception signal terminals to be discharged and allows rapid lowering of a potential at the terminal for antenna. In the SPDT switch, a switching characteristic is improved and a delay in the rising edge of a low-power slot which comes after a high-power slot is reduced.

Abstract: Switching characteristics in an SPDT switch are improved to reduce the rise delay in a low power slot following after a high power slot. Control terminals of an SPDT switch are respectively provided with backflow prevention circuits. The backflow prevention circuit is configured to have two transistors and a diode. In a transmission mode, for example, when a time slot where a high power passes through transistors is followed by a time slot where a low power passes through, the electric charges accumulated in the gates of the transistors are blocked. In the case where the transistors are in the OFF state, the electric charges accumulated in the gates of the transistors are immediately discharged to allow the transistors to be completely turned OFF.

Abstract: A method and system for diversity transmission from a mobile station. Signals sent from a mobile station to a base station may suffer from fading. To combat this, diversity transmission is used to compensate for the effects of fading and destructive multi-path interference by sending two or more signals. Signals to be transmitted from the mobile station are split into a first split signal and a second split signal and diversified from one another. Diversification of the split signals may be accomplished by modifying the phase of either the first split signal, the second split signal or both the first and second split signal. The diversified signals may then be transmitted from a first and second antenna.

Abstract: An efficient configurable signal filter. The filter includes a first mechanism for receiving a first signal of a first type and a second signal of a second type. A second mechanism selectively filters the first signal during a first mode of operation, and filters the second signal during a second mode of operation. A third mechanism generates control signals. A fourth mechanism automatically configures the second mechanism to operate in the first mode of operation or the second mode of operation based on the control signals. In a specific embodiment, the first type of signal is characterized by a first rate, and the second type of signal is characterized by a second rate. The first signal and the second signal are digital ADC outputs. The second mechanism includes plural filter blocks, each having one or more Multiply-Accumulate (MAC) pipes. Each of the one or more MAC pipes include one or more MAC blocks that are each associated with a coefficient memory data structure of a coefficient memory.

Abstract: An RF circuit module, in which a power amplifier and a transceiver are united, with reduced interference between its electronic circuit blocks, downsized and still having high performance, and with a stable performance not dependent on the ground land structure on the motherboard, is provided. The ground plane 110 for at least a last-stage amplifier 11 of the power amplifier 10 where the greatest power is generated in the whole RF circuit block, that is, the source of generating the greatest noise and heat for the RF circuit block, is isolated from the ground plane for at least one circuit portion of the transceiver 9 including an LNA 51, receiver 52, transmitter 30, and VCO 70. These ground planes are connected to a common ground plane 480 through different connection conductors, respectively.

Abstract: Apparatus for detecting the envelope of an RF signal that comprises an RF transistor operating essentially at a non-linear operating point at the RF frequency range; a DC power supply for feeding the RF transistor; a dummy load for terminating the output of the RF transistor; and at lease one impedance, through which the DC power supply feeds the RF transistor, for obtaining an indication signal developed across the impedance. The indication signal represents the envelope, from the fluctuating current drawn by the RF transistor from the DC power supply during the time period when the RF signal is applied to the feeding input.

Abstract: An apparatus for converting a signal from a first analog format to a second analog format. The apparatus has an input port, a first converter, filters, first mixers, second converters, and an output port. The input port is configured to receive the signal. The signal has the first analog format. In an embodiment, the first analog format complies with the SCTE 40 2003 technical standard. In an embodiment, the second analog format is a conventional analog format. The first converter is coupled to the port and is configured to convert the signal to a first digital format. The filters are coupled to the first converter and configured to isolate a first channel of the signal from a second channel of the signal. The first mixers are coupled to the filters and configured to expand the first channel and the second channel to a second digital format. The second converters are coupled to the first mixers and configured to convert the first channel and the second channel to the second analog format.

Abstract: In a mixer of a converter, a bipolar transistor is connected between the base of a bipolar transistor and a positive power-supply node within a driving circuit, as a temperature characteristic compensating circuit. When the ambient temperature of the driving circuit rises, collector current of the transistor is increased due to the temperature characteristic of the transistor. This lowers the drain voltage of a high electron mobility transistor. However, collector current of the transistor within the temperature characteristic compensating circuit is also increased, increasing the voltage at a point, so that the increase in the collector current of the transistor is suppressed. This results in a stabilized drain voltage of the transistor. Therefore, the low noise down-converter can supply a stable voltage to a transistor performing frequency conversion, without any effect from the change in the ambient temperature.

Abstract: The invention relates to a low-noise amplifier circuit and a method for amplifying low-power signals in a low-noise manner. Said signals are supplied to the inputs of several amplifiers (20 . . . 29) which are arranged in parallel. The output signals of said amplifiers (20 . . . 29) are multiplied by each other.

Abstract: The invention provides a signal processing semiconductor integrated circuit of the direct conversion system, which includes a dummy amplifier having the same circuit configuration as a low noise amplifier being the first stage amplifier, in which the DC offset calibrations on the subsequent stage amplifiers are carried out during shifting into the reception mode in a state that the low noise amplifier is deactivated and the dummy amplifier is activated. Thereby, the invention achieves to suppress generation of the DC offsets resulting from the leakage noises of the local oscillator during shifting into the reception mode, and to enhance the reception sensitivity.

Abstract: A reconfigurable baseband filter for use in a multimode communication system is disclosed. One or more filter elements can each be configured as a plurality of sub-elements. The value of each of the filter elements can be varied by switching between at least two of the plurality of sub-elements. Switching noise within a desired passband can be reduced by switching at a rate that is greater than the desired passband. The switching noise in the passband can be further reduced by pseudo-randomly switching between the sub-elements. The filter can use a delta-sigma modulator to generate a pseudo-random switching signal.

Abstract: A wireless signal amplification system including amplification apparatus (6) consisting of numerous different amplifiers (61 to 6n) which are distributed in an analogue processing chain (4). Also, a converter (12) for converting analogue signals into digital signals which, at input, are connected to the outlet of the analogue processing chain (4) and, at output, are connected to at least the gain control circuit (16) of the amplification apparatus (6) according to a value that is representative of a characteristic of the wireless signal (1). In this way, sampling of the wireless signal (1) by the converter (12) is optimized. The gain control circuit (16) establishes an average gain control signal (18), and also has, for each of the amplifiers (61 to 6n), a device for calculating an individual gain control signal (20i to 20n) according to a transfer function (H1 to Hn) which is specific to each amplifier and which is applied to the average gain control signal.

Abstract: A head of transmission-reception of a high-frequency signal made in the form of an integrated circuit including a transmit amplifier and a receive amplifier. The transmit terminal of the transmit amplifier and the receive terminal of the receive amplifier are interconnected in a common transmit/receive terminal. The head includes means for selecting one of the amplifiers and means for placing the other amplifier in a high impedance state, as seen from the transmit/receive terminal.

Abstract: Disclosed is a method and apparatus of transmit diversity that is backward compatible and does not significantly degrade performance in additive white guassan noise (AWGN) conditions using a transmission architecture that incorporates a form of phase sweep transmit diversity (PSTD) referred to herein as biased PSTD. Biased PSTD involves transmitting a signal and a frequency swept version of the same signal over diversity antennas at different power levels. By transmitting the two signals at different power levels, the depths of nulls normally seen in AWGN conditions when PSTD is utilized is reduced and performance degradation in AWGN conditions is mitigated.

Abstract: An audio production, satellite uplink and radio broadcast studio system includes an audio console having a supporting meter bridge and editing unit operative under the control of a central or main computer. The audio console is coupled to a plurality of analog audio information sources including a plurality of microphones, a plurality of telephone lines, a radio broadcast tuner and a plurality of audio tape drives. The audio console is further coupled to a plurality of digital information sources including a pair of ISDN lines, a plurality of compact disc players, a mini-disc player and a remotely operated digital audio recorder. The computer is coupled to the audio console via an interface and sound card. The audio console is coupled to a plurality of program outputs having different program format capabilities and to a distribution amplifier operative to control the various remotely operated recording apparatus within the system.

Abstract: A pin layout which prevents degradation of a frequency characteristic of a low noise amplifier and a receiving mixer included in a semiconductor integrated circuit for dual-band transmission/reception wherein the circuit of the low noise amplifier is provided at a position where the distance from a end of the pin outside the package of the low noise amplifier to the pad is the shortest; ground pins of two low noise amplifiers and the high frequency signal pins are arranged respectively so as not to be adjacent to each other; the power source and ground pin of the low noise amplifier, and the power source and ground pin of the bias circuit are respectively separated; and high frequency signal wires do not intersect each other.

Abstract: A wireless communications device includes an amplifier module configured to amplify a signal. The amplifier module includes a serial arrangement of amplifiers. Each of the amplifiers are designed to operate with increased efficiency for different power level ranges. The amplifiers are connectable via controllable switches. A controller, in communication with the controllable switches, selectively connects the amplifiers to increase the efficiency of the amplifier module.

Abstract: A digital signal processing architecture for an audio system combines multiple functions in programmable and reconfigurable blocks to achieve an efficient use of hardware and chip area. AM, FM, and audio functions can be performed using the same reconfigurable hardware while taking into account the different sample rates and processing functions required for each.

Abstract: A radio receiver with a potentiometer as the volume control is described, wherein an unintentional displacement of the potentiometer during the switched-off phase becomes effective only with a delay when the radio receiver is switched on by means of a switch which is separate from the potentiometer.

Abstract: A receiver for receiving reception signals of a first type, for example, TV signals, and reception signals of a second type, for example, FM-radio signals. The receiver may be used in multimedia applications. In the receiver, a single tuner TUN frequency converts a reception signal RFS into an intermediate frequency signal IFS. For relatively small-size implementations, the receiver is a single conversion receiver for both types of reception signals, the single conversion being effected in the tuner TUN. Depending on whether a first-type or second-type reception signal is desired, the tuner TUN provides the intermediate frequency signal IFS at a first intermediate frequency IF1 or a second intermediate frequency IF2, respectively. The intermediate frequency signal IFS at intermediate frequency IF1 is processed in a first intermediate frequency signal processor IFSP1.

Abstract: A technique for reducing FM intrusion in an AM section of an AM/FM receiver. In one embodiment, a first switch is provided between an FM tuner filter circuit and an AM tuner circuit. A second switch is provided between the FM tuner circuit and a reference potential. When the receiver is in an FM mode, the first switch is closed so that a tuning voltage can be applied to the FM tuner circuit, and the second switch is open to prevent the tuning voltage from being affected by the reference potential. When the receiver is switched to the AM mode, the first switch is open to prevent intermodulation product signals generated by the FM tuner circuit from reaching the AM tuner circuit, and the second switch is closed to connect the FM tuner circuit to the reference potential. By connecting the FM tuner circuit to the reference potential when the receiver is in the AM mode, the tuning of the FM tuner circuit is shifted out of the FM bandwidth, thus eliminating intermodulation products at the AM frequencies.

Abstract: A microcomputer in a radio frequency (RF) signal receiver, such as a cordless telephone set, periodically samples a received baseband audio signal to determine its frequency content. The microcomputer uses at least one predetermined frequency threshold value, and determines that the RF signal is present if the output signal contains signals no higher in frequency the frequency threshold value, and determines that the RF signal is absent if the output signal contains signals higher in frequency than the frequency threshold value. The circuit is useful in either a base unit or a handunit of a cordless telephone set.

Abstract: A control channel is searched for call waiting in a mobile station where the power supply for a receiving circuit is turned off during a break time of receiving level measurements, wherein in a first control channel selection mode, all the control channels are divided into a plurality of groups, the receiving levels of the control channels are measured group by group intermittently and sequentially. The intermittent measurement of these groups are repeated until a control channel having a receiving level equal to or greater than a first predetermined value is detected. When a receiving level equal to or greater than the first predetermined value is detected, the receiving levels of all the control channels are measured in a second control channel selection mode.

Abstract: A digital mixer-filter-decimator (MFD) is disclosed which is reconfigurable so that it can be used in both modes of operation of a dual mode receiver such as an AM/FM receiver. In either mode of operation the MPD performs filtering and decimation operations on separate data streams containing alternate samples of a digital input data stream. In the FM mode a mixing operation is also enabled to produce a complex output comprising in-phase and quadrature components. The mixing operation is disabled in the AM mode and the filtered and decimated outputs are combined to provide a real output. The same decimator filter can be used in both modes.

Abstract: An improved tuner for a varactor-tuned local oscillator in a radio receiver includes a winding of a pair of magnetically coupled inductors, preferably constructed in the form of a transformer. Preferably, the first and second windings are magnetically coupled with reduced inter-winding capacitance by axially separating the windings on a common core. The second winding is selectively coupled by a switch to a capacitive load in order to change the inductance of the first winding. The tuning range of the resonant circuit formed by the varactor diode set and the first winding is changed when the capacitive load is coupled. The magnetic coupling between the transformer windings provides DC isolation between the oscillator and the switching circuit. Preferably, a tuning actuator has overlapping ranges of movement for selection of a signal within both the AM and FM frequency bands as the intermediate frequencies for the local oscillator are generated.

Abstract: A low-pass passive filter is inserted in the phase locked loop of a voltage-controlled oscillating circuit having a varactor diode. The filter has a first resistor, a capacitor and a second resistor connected in that order and the blocking characteristics of the filter are changed in accordance with a selected value of the second resistor. A push-pull output circuit in which the upstream transistor is connected directly to the supply voltage line receives the signal from a phase comparator circuit (which is indicative of the result of phase comparison) and outputs it to the low-pass passive filter. The low-pass passive filter controls the terminal voltage of the varactor diode in accordance with the terminal voltage of the capacitor and the value of the second resistor is selected depending on the desired blocking characteristics of the filter.