Ericsson Gmbh

Xue-Song Zhou

Ross W Lampe, Jr

Rodney A Dolman

Yawei Ma

Scott R Justice

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.

Voltage controlled oscillator with partial load-pull tuning

A three-way switch for individually connecting either a dummy load, a first antenna, or a second antenna to a radio transmitter power amplifier output. The switch includes a first member connected to a dummy load and a second flexible member fixed in position relative to the first member and biased against the first member so as to make an electrical connection between the first and second member. The second member is connected to the radio transmitter output and includes two contact areas for connecting to a first and a second antenna. When a first antenna is applied against the first contact area, the transmitter is disconnected from the dummy load and only the first antenna is connected to the transmitter output. When a second antenna is applied to the second contact area the flexible member of the switch disconnects from the first antenna and only the second antenna is connected to the transmitter output.

Three-way switch for protection of a power amplifier during antenna

Reduction of transmitter exciter chain generated noise from the receive bank of a portable/hand-held duplex transceiver is achieved using a high output power, low-noise voltage-controlled-oscillator (VCO) in the transmitter exciter chain. Using this high-power, low-noise oscillator as the RF source in the transmitter exciter chain precludes the need for the conventional buffer/driver amlplifier stage and an associated inter-stage noise filter. Elimination of buffer/driver stage components and bulky inter-stage noise filter components allows complete integration of transmitter exciter chain components resulting in reduced size and cost.

Method and apparatus for reducing receive band transmitter-chain noise

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. The buffer amplifier is a linear amplifier including a transistor, and the active part and the buffer amplifier may be connected by a capacitance for reducing coupling between the active part and the buffer amplifier.

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Chapel Hill, NC, United States of America

Xue-Song Zhou