A variable capacitor device comprises first and second control paths which are configured to enable differential control using first and second transistors of a same doping type in the first and second control paths, respectively, wherein the first and second transistors are configured as voltage variable resistors for tuning a capacitance of the variable capacitor device.

Methods and apparatus for storing a control voltage of a phased-locked loop (PLL) when switching from mission mode to standby mode for the PLL, and for restoring the control voltage of the PLL when switching back to mission mode. An example PLL circuit includes a charge pump, a voltage-controlled oscillator (VCO) having a control input coupled to an output of the charge pump via a node, and a tracking circuit coupled to the node. The tracking circuit is generally configured to sample a voltage of the node during a mission mode, save a representation of the sampled voltage before entering a standby mode, and restore the sampled voltage to the node for reentering the mission mode using the saved representation of the sampled voltage.

Various embodiments of the invention relate to a Multi-Band Voltage Controlled Oscillator (VCO). The multi-band VCO features a coupled-inductor based resonator. The resonator comprises a primary path and a secondary path inductively coupled to the primary path. The primary path comprises multiple LC tuning stages coupled in series with each stage having an adjustable capacitor and a primary inductor inductively coupled to the secondary path. The secondary path comprises multiple secondary inductors inductively coupled to respective primary inductors in the primary path. Furthermore, the secondary path comprises a plurality of controllable switches which are controlled to switch ON or OFF simultaneously to engage/disengage the inductive coupling between the primary path and the secondary path. Incorporating multiple LC tuning stages lowers voltage swing across each tuning stages, thus minimizing phase noise caused by nonlinearity in the resonator.

In accordance with an embodiment, a method of operating a voltage controlled oscillator (VCO) that having a VCO core coupled to a filtered current source includes setting an oscillation frequency of the VCO core based on a tuning signal received at a tuning signal input; and setting a resonant frequency of the filtered current source based on the received tuning signal using a tuning circuit having an input directly connected to the tuning signal input.

Methods and systems are provided for calibrating voltage-controlled oscillators (VCOs). frequency control information, relating to output frequency of a VCO, which varies based on changes in operational conditions, may be determined. The frequency control information enables indicating the output frequency within a range of allowable values for control inputs and a range of expected values based on the operational conditions. For each control input setting, calibration control information for a calibration voltage associated with a control input, may be determined, based on the frequency control information, with respect to the operational conditions, to generate a constant output frequency. The operational conditions may be assessed, and a calibration voltage corresponding to the assessed operational conditions may be determined. The calibration voltage may be applied, and based on applying the calibration voltage, a tuning control input for tuning the constant output frequency may be determined and applied to the VCO.

An apparatus is provided which comprises: an oscillator circuit to generate a clock signal and transmit the clock signal over a signal line; a ground reference plane associated with the signal line; and one or more patterns formed in the ground reference plane, wherein the one or more patterns in the ground reference plane is to filter out noise from the clock signal transmitted over the signal line.

A voltage-controlled oscillator includes an oscillation generator, two inductors and two amplifiers. The oscillation generator generates two oscillation voltage signals based on a control voltage. Each inductor receives a respective oscillation voltage signal, and provides a respective input voltage signal. Each amplifier generates a respective current signal based on a respective input voltage signal. When one of the current signals has a magnitude that varies according to a magnitude of the respective input voltage signal, the other of the current signals has a constant magnitude. The current signals are combined into an output current signal at a common node of the amplifiers.

Methods and apparatus for storing a control voltage of a phased-locked loop (PLL) when switching from mission mode to standby mode for the PLL, and for restoring the control voltage of the PLL when switching back to mission mode. An example PLL circuit includes a charge pump, a voltage-controlled oscillator (VCO) having a control input coupled to an output of the charge pump via a node, and a tracking circuit coupled to the node. The tracking circuit is generally configured to sample a voltage of the node during a mission mode, save a representation of the sampled voltage before entering a standby mode, and restore the sampled voltage to the node for reentering the mission mode using the saved representation of the sampled voltage.

A flash analog-to-digital converter (ADC) receives an input control signal and performs coarse tuning of a frequency of an output signal, produced between first and second nodes having an inductance coupled therebetween. The flash ADC quantizes an operating frequency range for the output signal produced between the first and second nodes as M.Math.?f, where M is an integer from 0 to N?1, where N is a number of intervals into which a frequency range for the output signal is divided, and where ?f is a resulting frequency step produced by the quantizing. The value of M is generated based upon the input control signal and a word controlling switches of a plurality of switched capacitance circuits associated with the first and second nodes to close ones of those switches associated with the control word to coarsely tune the frequency of the output signal.

In accordance with an embodiment, a method of operating a voltage controlled oscillator (VCO) includes generating a first oscillating signal in a first VCO core and generating a second oscillating signal in a second VCO core, such that the first oscillating signal and the second oscillating signal have a same frequency and a fixed phase offset. The VCO includes the first VCO core and the second VCO core, and each VCO core includes a pair of transistors. The VCO also includes a transformer having a first winding coupled between control nodes of the pair of transistors of the first VCO core and a second winding coupled between control nodes of the pair of transistors of the second VCO core.