A voltage-controlled oscillator (VCO) includes a power supply node configured to have a power supply voltage. A reference node is configured to have a reference voltage. A transformer-coupled band-pass filter (BPF) is coupled to a pair of transistors. The pair of transistors and the transformer-coupled band-pass filter are positioned between the power supply node and the reference node.

A resonant tank includes a first capacitor formed on a semiconductor substrate, a first inductor formed on the semiconductor substrate, a second capacitor formed on the semiconductor substrate, and a second inductor formed on the semiconductor substrate. The first capacitor, the first inductor, the second capacitor, and the second inductor are connected in a ring configuration, with each capacitor connected between a pair of the inductors and with each inductor connected between a pair of the capacitors. An amplifier circuit is coupled to the resonant tank and configured to amplify a signal in the resonant tank.

An apparatus includes a digitally controlled oscillator (DCO), which includes an inductor coupled in series with a first capacitor. The DCO further includes a second capacitor coupled in parallel with the series-coupled inductor and first capacitor, a first inverter coupled in parallel with the second capacitor, and a second inverter coupled back-to-back to the first inverter. The DCO further includes a digital-to-analog-converter (DAC) to vary a capacitance of the first capacitor.

A novel and useful mm-wave frequency generation system is disclosed that takes advantage of injection locking techniques to generate an output oscillator signal with improved phase noise (PN) performance and power efficiency. Low frequency and high frequency DCOs as well as a pulse generator make up the oscillator system. A fundamental low frequency (e.g., 30 GHz) signal and its sufficiently strong higher (e.g., fifth) harmonic (e.g., 150 GHz) are generated simultaneously in a single oscillator system. The second high frequency DCO having normally poor phase noise is injected locked to the first low frequency DCO having good phase noise. Due to injection locking, the high frequency output signal generated by the second DCO exhibits good phase noise since the phase noise of the second DCO tracks that of the first DCO.

The present application relates to a differential Colpitts voltage-controlled oscillator (VCO) circuit, which comprises a pair of transistors with control terminals biased by a common biasing voltage and a pair of couplers arranged to cross-couple corrector/drain of the transistors and the base/gate of the differential transistors. The pair of couplers have a coupling factor k.sub.c, which used to enhance the transconductance of the transistor pair, therefore can be used for power consumption reduction and phase noise minimalization.

A differential Colpitts oscillator circuit is described which provides a larger tuning range, has better phase noise and uses less power than conventional differential Colpitts oscillator circuits. The circuit is characterized by a capacitive ladder in which only variable capacitor is used for tuning the circuit. In some embodiments, a variable capacitor can be used for fine tuning.

A differential Colpitts oscillator circuit is described which has center-tapped inductors which are cross-coupled with gates of second transistors of first and second transistor pairs which can reduce the minimum power supply voltage and the bias voltage for the circuit. In addition, a capacitive ladder can be implemented which also has the potential benefit of increased tuning range.

An inductive switch comprises an inductor that has a primary metallic winding having a boundary configured in shape of a figure eight, such as in two loops, and a plurality of secondary metallic windings arranged within the boundary of the primary metallic winding. The inductive switch includes a plurality of switches, each switch arranged in series with a respective one of the plurality of secondary metallic windings. An equal number of the secondary windings is arranged within each loop. A tunable inductor comprises at least one main metallic loop and at least one secondary metallic loop, wherein the at least one secondary metallic loop comprises a switch that is arranged to configure the at least one secondary metallic loop into at least one shorted metallic loop or at least one closed metallic loop. The at least one shorted loop is floating.

A voltage controlled oscillator includes a variable capacitance circuit having a plurality of variable capacitance elements, each having a capacitance that is a function of a tuning voltage, two or more oscillator core circuits, each operable over a specified frequency band, and inductive elements connected between the variable capacitance circuit and the oscillator core circuits.

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.