Voltage-controlled oscillator

About: Voltage-controlled oscillator is a research topic. Over the lifetime, 23896 publications have been published within this topic receiving 231875 citations. The topic is also known as: VCO.

A Low Phase Noise Quadrature LC VCO Using Capacitive Common-Source Coupling

Abstract: A low phase noise quadrature LC VCO with inherent tail-current shaping is presented. Two identical differential LC VCOs are locked in quadrature with a capacitor connected between their common-source nodes. This capacitor further drives the oscillators into a tail-current shaping mode, which increases their oscillation amplitude and reduces their phase noise. A multi-band 1.9 GHz differential nMOS quadrature LC VCO prototype has been fabricated in a 0.25 ?m BiCMOS process. The measured phase noise is -124.4 dBc/Hz at a 1 MHz offset from a 2.07 GHz carrier while the circuit dissipates only 3 mW from a 1.5 V supply. The quadrature VCO is tunable from 1.75 GHz to 2.1 GHz and the VCO core only occupies 0.625mm2.

Voltage controlled oscillator

Abstract: Embodiments of the present invention provide a method of centering an operating band of a voltage controlled oscillator around a desired operating frequency. In one embodiment, an adjustable feedback divider provides for driving an output signal to the top and bottom of the operating band. An adjustable period divider and counter provide a plurality of count values for use in determining a mid-point of the operating band. A capacitance bank provides for selectively adjusting a capacitance of the voltage controlled oscillator, thereby adjusting the operating band.

Multiple-band mobile transceiver having a smaller number of local oscillators

Abstract: A frequency synthesizer consists of a voltage-controlled oscillator and a frequency division and distribution section. The frequency division and distribution section, which splits an oscillation signal of the voltage-controlled oscillator into a transmission modulation local oscillation signal and a reception second local oscillation signal while frequency-dividing the oscillation signal of the voltage-controlled oscillator, includes two pairs of frequency dividers and two switches. The frequency division numbers of the two pairs of frequency dividers are so set as to accommodate all the combinations of mobile communications systems and the transmission modulation local oscillation signal/reception second local oscillation signal. The two switches are switched in accordance with a mobile communications system for which a mobile transceiver is operating. The two local oscillation signals are input to a quadrature modulator and a quadrature demodulator, respectively.

Fractional-N frequency synthesizer and method

Abstract: A fractional-N frequency synthesizer is based on a PLL which employs a multi-phase VCO and a multi-phase frequency divider to provide a desired fractional-N divider ratio. The multi-phase frequency divider includes a multi-modulus divider which divides a VCO output waveform with a division ratio that varies in response to a modulus control signal. The divided output is delayed to produce a plurality of outputs, each of which has a respective phase that corresponds with the phase of a respective VCO output. A phase selector provides a selected one of the outputs to the PLL's phase detector in response to a phase control signal such that the multi-phase frequency divider provides a fractional-N division ratio. To reduce fractional spurs, a modulator randomizes the modulus and phase control signals, which serves to randomize and thereby reduce phase mismatch error which might otherwise be present in the frequency synthesizer's output.

Dual mode receiver

Abstract: A transponder including a receiver and a transmitter controlled by the output of the receiver, with the receiver including a first phase locked loop with a mixer and a voltage controlled oscillator supplying an output to a second phase locked loop including a switchable frequency divider connected to supply a low side injection signal to the mixer of the first loop in the first mode of operation and a high side injection signal to the mixer in the second mode of operation.