An integrated circuit includes at least two identical, synchronous and independent oscillator circuits that are coupled one to one in parallel with each other at homologous oscillating nodes of the respective oscillator circuits. The coupling in parallel is made using at least one coupling track that is configured so as to not introduce any phase shift or to introduce a very small phase shift.

A variable capacitor circuit includes a capacitor block including a first varactor element comprising a first transistor having a first size, a second varactor element comprising a second transistor having a second size different from the first size, a first terminal commonly connected to a source and a drain of the first transistor, a second terminal commonly connected to a source and a drain of the second transistor, and an RC circuit connected to a gate of the first transistor and a gate of the second transistor.

A voltage controlled oscillator (VCO) includes: a pair of inductors coupled in series; a first pair of varactors coupled in series, and a second pair of varactors coupled in series. A first common mode node is between the respective varactors of the first pair of varactors and a second common mode node is between the respective varactors of the second pair of varactors. A supply voltage node is switchably coupled to the first common mode node through a first switch, the supply voltage node being a node located between the pair of inductors. A control voltage node (V.sub.c) is switchably coupled to the second common mode node through a second switch.

A transformer based voltage controlled oscillator (VCO) is provided with a primary resonant circuit having a first inductor connected in parallel with a variable first capacitance circuit. A secondary resonant circuit is formed from a second inductor connected in parallel with a variable second capacitance circuit, and also includes a mode control circuit. The mode control circuit controls the direction of current flow through the secondary resonant circuit inductor. The first and second inductors are inductively mutually coupled in either an even mode or an odd mode in response to the mode control circuit. The VCO supplies a first resonant frequency in response to even mode operation, or a second resonant frequency, greater than the first resonant frequency, responsive to odd mode operation. The VCO may include a first electrically tunable varactor shunted across the first capacitance circuit and a second electrically tunable varactor shunted across the second capacitance circuit.

An oscillator includes a first output node and a second output node. There is a tank circuit coupled between the first output node and the second output node. There is a first transistor having a first node, a second node coupled to a current source, and a control node coupled to the second output node. There is a second transistor having a first node, a second node coupled to the current source, and a control node coupled to the first output node. There is a first inductor coupled in series between the first node of the first transistor and the first output node. There is a second inductor coupled in series between the first node of the second transistor and the second output node.

An ultra-wideband radio frequency transmission system capable of receiving a first signal with discrete levels, and including: a voltage-controlled oscillator capable of supplying a first oscillating signal including an oscillating circuit powered by a power supply circuit comprising at least one first current source controlled by the first signal with discrete levels or a second signal with discrete levels obtained from the first signal with discrete levels; a mixer capable of receiving the first oscillating signal and of supplying a second oscillating signal equal to the first oscillating signal multiplied by a gain which depends on the first signal with discrete levels or on a third signal with discrete levels obtained from the first signal with discrete levels; and an antenna or an electromagnetic coupling device capable of transmitting a radio frequency signal based on the second oscillating signal.

An oscillator circuit has a reconfigurable oscillator amplifier. The reconfigurable oscillator amplifier is used to be coupled to a resonant circuit in parallel. The reconfigurable oscillator amplifier supports different circuit configurations for different operation modes, respectively. The reconfigurable oscillator amplifier has at least one circuit component shared by the different circuit configurations. The reconfigurable oscillator amplifier employs one of the different circuit configurations under one of the different operation modes.

An oscillator circuit includes a current source, an oscillating section, a first capacitor, and a setting section. The current source is coupled to a connection node, and is configured to cause a current having a current value based on an input voltage to flow from a first power node to the connection node. The oscillating section is provided on a current path between the connection node and a second power node. The oscillating section is configured to oscillate at an oscillation frequency based on a current flowing through the current path. The first capacitor is provided between the connection node and the second power node. The first capacitor has a capacitance that varies in accordance with a voltage at the connection node. The setting section is configured to perform variation operation on the basis of the voltage at the connection node. The variation operation is operation of varying an impedance between the connection node and the second power node.

A quadrature voltage-controlled oscillator circuit with phase shift includes two voltage-controlled oscillators with the same structure, wherein the two voltage-controlled oscillators are connected to each other through input and output ports, and the two voltage-controlled oscillators respectively include a cross-coupled oscillating circuit, an injection locking circuit, a resonant circuit and a voltage-controlled current source circuit which are electrically connected to each other; and signals are injected through the injection locking circuit and coupled with the oscillating circuit, so as to output a quadrature signal. An oscillator is enabled to operate stably in one mode by means of a simple circuit structure, and a good phase shift can be provided for the resonant circuit in a lower frequency band; and meanwhile, a tuning range of the oscillator is improved without increasing phase noise.

A voltage-controlled oscillator (VCO), includes a resonator circuit connected to receive an input voltage and having a first output node and a second output node; and at least one cross-coupled switching circuit portion, each cross-coupled switching circuit portion comprising a first transistor having a drain connected to the first output node and a second transistor having a drain connected to the second output node, the first transistor having a gate connected between the drain of the second transistor and the second output node and the second transistor having a gate connected between the drain of the first transistor and the first output node, each of the first and second transistors having a threshold voltage that is determined to be the highest threshold voltage available for the process used to create the VCO.