An oscillator includes a tunable resonant circuit having an inductance and a variable capacitance coupled between first and second nodes, and a set of capacitances selectively coupleable between the first and second nodes. An input control node receiving an input control signal is coupled to the variable capacitance and set of capacitances. The tunable resonant circuit is tunable based on the input control signal. A biasing circuit biases the tunable resonant circuit to generate a variable-frequency output signal between the first and second nodes. A voltage divider generates a set of different voltage thresholds, and a set of comparator circuits with hysteresis compares the input control signal to the set of different voltage thresholds to generate a set of control signals. The capacitances in the set of capacitances are selectively coupleable between the first and second nodes as a function of control signals in the set of control signals.

Voltage-controlled oscillation circuitry includes multiple cores and multiple mode or gain boosters coupled between the multiple cores. To prevent an undesired operating mode of the voltage-controlled oscillation circuitry from dominating a desired operating mode (e.g., an in-phase operating mode or an out-of-phase operating mode), the mode boosters may increase a desired gain of the desired operating mode and decrease an undesired gain of the undesired operating modes. In particular, mode boosters coupled to terminals of the cores that are associated with the desired operating mode may be enabled, while mode boosters coupled to terminals of the cores that are associated with the undesired operating mode may be disabled.

A VCO (voltage-controlled oscillator) includes: a resonant tank having a parallel connection of an inductor, a fixed capacitor, a variable capacitor, a first temperature compensating capacitor, and a second temperature compensating capacitor across a first node and a second node, and configured to establish an oscillation of a first oscillatory voltage at the first node and a second oscillatory voltage at the second node; and a regenerative network placed across the first node and the second node to provide energy to sustain the oscillation. The variable capacitor is controlled by a control voltage, the first temperature compensating capacitor is controlled by a first temperature tracking voltage of a positive temperature coefficient, and the second temperature compensating capacitor is controlled by a second temperature tracking voltage of a negative temperature coefficient.

Embodiments herein relate to an apparatus and method for calibrating a notch filter which filters a power supply signal for a voltage-controlled oscillator (VCO). In one aspect, a control circuit performs a number of calibration cycles for the filter to determine a value of a calibration code for the filter which minimizes a change in a frequency of the output signal of the VCO due to a change in the voltage of the power supply signal. After each calibration cycle, the calibration code is adjusted based on whether the frequency of the output signal increase or decreases. The calibration cycles can therefore converge on an optimal calibration code which minimizes the change in frequency due to the change in voltage. This minimizes a sensitivity of the VCO to noise in the power supply signal.

Embodiments disclosed herein relate to oscillators including methods of operating the same, for example for use in radio frequency circuits. In an embodiment, an oscillator has cross-coupled transistors connected between a resonant circuit and a tail circuit. The resonant circuit and tail circuit have respective supply connections for powering the oscillator with an external power supply and the cross-coupled transistors have a bias circuit coupled to respective gates of the cross-coupled transistors and arranged to bias said transistors in an active region of operation. The tail circuit has a current source, a tail capacitor and a tail resistor coupled between a common node of the cross-coupled transistors and the supply connection of the tail circuit.

The invention relates to a resonator circuit, the resonator circuit comprising a transformer comprising a primary winding and a secondary winding, wherein the primary winding is inductively coupled with the secondary winding, a primary capacitor being connected to the primary winding, the primary capacitor and the primary winding forming a primary circuit, and a secondary capacitor being connected to the secondary winding, the secondary capacitor and the secondary winding forming a secondary circuit, wherein the resonator circuit has a common mode resonance frequency at an excitation of the primary circuit in a common mode, wherein the resonator circuit has a differential mode resonance frequency at an excitation of the primary circuit in a differential mode, and wherein the common mode resonance frequency is different from the differential mode resonance frequency.

Phase-locked loop circuitry generates an output signal based on transformer based voltage controlled oscillator (VCO) circuitry. The VCO circuitry includes upper band circuitry including first oscillation circuitry, a first harmonic filter circuitry coupled to the first oscillation circuitry, and a first selection transistor coupled to the first harmonic filter circuitry and a current source. The first harmonic filter circuitry filters the output signal. The lower band circuitry includes second oscillation circuitry, a second harmonic filter circuitry coupled to the second oscillation circuitry, and a second selection transistor coupled to the second harmonic filter circuitry and the current source. The second harmonic filter circuitry filters the output signal.

Disclosed herein is a tunable resonant circuit including an inductance directly electrically connected in series between first and second nodes, a variable capacitance directly electrically connected between the first and second nodes, and a set of switched capacitances coupled between the first and second nodes. The set of switched capacitances includes a plurality of capacitance units, each capacitance unit comprising a first capacitance for that capacitance unit directly electrically connected between the first node and a switch and a second capacitance for the capacitance unit directly electrically connected between the switch and the second node. Control circuitry is configured to receive an input control signal and connected to control the switches of the set of switched capacitances. A biasing circuit is directly electrically connected to the tunable resonance circuit at the first and second nodes.

A voltage-controlled oscillator includes a first transistor, a second transistor, a first center-tapped inductor, two first varactors, a second center-tapped inductor and two second varactors. The first and second transistors cooperatively forma cross-connected pair. The first center-tapped inductor and the first varactors cooperatively form a first LC tank. The second center-tapped inductor and the second varactors cooperatively forma second LC tank. The cross-connected pair is connected between the first and second LC tanks. The first and second center-tapped inductors are mutual-inductively coupled to each other. An oscillation signal pair is provided between the first LC tank and the cross-connected pair.

A voltage-controlled oscillator device includes first and second voltage-controlled oscillators, a first switch group including two first switches, and a second switch group including two second switches. The first voltage-controlled oscillator includes a first inductor group, a first negative resistance circuit and a first voltage output terminal group. The second voltage-controlled oscillator includes a second inductor group, a second negative resistance circuit and a second voltage output terminal group. For the first switch group, first control terminals are electrically connected to the first voltage output terminal group, first input terminals are electrically connected to the second voltage output terminal group, first output terminals are electrically connected. For the second switch group, second control terminals are electrically connected to the second voltage output terminal group, second input terminals are electrically connected to the first voltage output terminal group, second output terminals are electrically connected.