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 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 quadrature oscillator includes a first oscillator that outputs a first differential signal, and a second oscillator that outputs a second differential signal having phases that are different from those of the first differential signal, wherein the first oscillator includes a first LC resonator having an inductor and a capacitor coupled in parallel, a first cross-coupled circuit having a first pair of cross-coupled transistors coupled to the first LC resonator, a first tail current source coupled to the first pair of transistors, first input differential pair transistors to which the second differential signal is to be input, and a first pair of harmonic resonators disposed in input sections of the first input differential pair transistors, the first pair of the harmonic resonators have a resonance frequency of an odd multiple of a resonance frequency of the first oscillator.

An oscillator is provided with an oscillator circuit having tank circuit terminals for coupling to a tank circuit. A microelectromechanical system (MEMS) resonator serves as a tank circuit. The MEMS resonator is coupled to the oscillator circuit using a transformer with a primary coil coupled to the oscillator tank circuit terminals and a secondary coil coupled to the MEMS resonator terminals, wherein the transformer has a turns ratio of N:1 and N is greater than 1.

A quadrature oscillator includes a first oscillator that outputs a first differential signal, and a second oscillator that outputs a second differential signal having phases that are different from those of the first differential signal, wherein the first oscillator includes a first LC resonator having an inductor and a capacitor coupled in parallel, a first cross-coupled circuit having a first pair of cross-coupled transistors coupled to the first LC resonator, a first tail current source coupled to the first pair of transistors, first input differential pair transistors to which the second differential signal is to be input, and a first pair of harmonic resonators disposed in input sections of the first input differential pair transistors, the first pair of the harmonic resonators have a resonance frequency of an odd multiple of a resonance frequency of the first oscillator.

The present disclosure describes aspects of a switchable inductor network for wideband circuits. In some aspects, the switchable inductor network provides selectable inductance. The switchable inductor network includes a first coil and a second coil that includes a first inductive segment and a second inductive segment. Connection points of the second coil connect the second coil across a portion of the first coil. The switchable inductor network also includes a switch connected between the first inductive segment and the second inductive segment of the second coil. The switch is configured to change the selectable inductance of the switchable inductor network by selectively coupling the first inductive segment to the second inductive segment of the second coil in response to a control signal.

An oscillator is provided with an oscillator circuit having tank circuit terminals for coupling to a tank circuit. A microelectromechanical system (MEMS) resonator serves as a tank circuit. The MEMS resonator is coupled to the oscillator circuit using a transformer with a primary coil coupled to the oscillator tank circuit terminals and a secondary coil coupled to the MEMS resonator terminals, wherein the transformer has a turns ratio of N:1 and N is greater than 1.

The present disclosure describes aspects of a switchable inductor network for wideband circuits. In some aspects, the switchable inductor network provides selectable inductance. The switchable inductor network includes a first coil and a second coil that includes a first inductive segment and a second inductive segment. Connection points of the second coil connect the second coil across a portion of the first coil. The switchable inductor network also includes a switch connected between the first inductive segment and the second inductive segment of the second coil. The switch is configured to change the selectable inductance of the switchable inductor network by selectively coupling the first inductive segment to the second inductive segment of the second coil in response to a control signal.