A circuit for calibrating an injection locked oscillator is provided. The injection locked oscillator includes an injection locking input, an LC tank and an oscillator output to output an oscillator output signal. The circuit is configured to adjust a capacitance of the LC tank to different values, detect an amplitude of the oscillator output signal for each value of the different values of the capacitance while an input signal having a target frequency is applied to the injection locking input, determine a maximum amplitude of the detected amplitudes, and select a value for operating the injection locked oscillator based on the determined maximum amplitude.

Radio frequency (RF) amplifiers, such as power amplifiers, are provided herein. In certain configurations, an RF amplifier includes an input terminal that receives an RF input signal, an output terminal that provides an RF output signal, an injection-locked oscillator driver stage that amplifies the RF input signal to generate an injection-locked RF signal, and a stacked output stage that further amplifies the injection-locked RF signal to generate the RF output signal. The stacked output stage includes a stack of at least a first transistor and a second transistor in series with one another. Thus, the stacked output stage is operable over a wide range of supply voltage to overcome the relatively low breakdown voltages of scaled transistors. Moreover, the injection-locked oscillator driver stage provides the RF amplifier with excellent power efficiency, including in applications in which the stacked output stage operates with a supply voltage that is variable.

An apparatus for radio-frequency (RF) oscillation signal production is disclosed. In example implementations, an apparatus includes an oscillator. The oscillator includes multiple oscillation stages that are coupled together in series into a ring. A respective oscillation stage of the multiple oscillation stages includes a transconductance amplifier and a core oscillator. The transconductance amplifier is coupled to a preceding oscillation stage. The core oscillator is coupled to the transconductance amplifier and to a succeeding oscillation stage, with the core oscillator including at least one output node configured to provide a respective output signal. In some implementations, at least one capacitor is coupled across at least the transconductance amplifier. In some aspects, at least one transistor of the transconductance amplifier is implemented with a silicon-on-insulator metal-oxide-semiconductor (SOI MOS) device that includes at least one back-gate terminal.

Embodiments of clock circuits disclosed herein include a crystal oscillator circuit, an injection oscillator coupled to kick-start the crystal oscillator circuit and a digital frequency calibration circuit coupled to recalibrate the injection oscillator. The crystal oscillator circuit is configured to generate a clock signal at a resonant frequency. The injection oscillator is coupled to supply an oscillation signal at an injection frequency to the crystal oscillator circuit to reduce a start-up time of the crystal oscillator circuit. The digital frequency calibration circuit is coupled to receive the resonant frequency and the injection frequency as inputs, and configured to supply a digital control signal to the injection oscillator to set the injection frequency of the injection oscillator substantially equal to the resonant frequency of the crystal oscillator circuit. Methods are provided herein to recalibrate the injection frequency of an injection oscillator over time, temperature and/or supply voltage.

There is described a device for generating electromagnetic field oscillation in a RF device or cavity. The device generally has a photo-diode configured for receiving a laser pulse train and emitting a first electrical signal based thereon, the first electrical signal having a plurality of frequencies; and a harmonics selector configured to output a second electrical signal having one or more frequency of the first electrical signal, the one or more frequency being selected in a manner for the output to generate the electromagnetic field oscillation in the RF device or cavity.

An oscillating circuit has an injection-locked oscillator (ILO) and a calibration circuit. The ILO has a Gm cell and an LC tank. A first node of the Gm cell receives a first injection signal, and a second node of the Gm cell receives a second injection signal. The first injection signal and the second injection signal are differential signals. The Gm cell provides a negative resistance between a first output end and a second output end of the Gm cell. When the calibration circuit tunes a resonant frequency of the LC tank of the ILO, the magnitude of the negative resistance is reduced to control the ILO to stop self-oscillating. After finishing tuning the resonant frequency of the LC tank, the calibration circuit controls the ILO to start self-oscillating by increasing the magnitude of the negative resistance.

A dual-mode oscillator and a multi-phase oscillator includes a mode switching circuit to switch between two operating modes and obtain oscillation signals having two different bands. The dual-mode oscillator also includes two transformer-coupled oscillators with each having a step-up transformer. The step-up transformer multiplies a drain voltage swing of a first metal oxide semiconductor (MOS) transistor and then injects a voltage signal to a gate of a second MOS transistor to obtain a larger gate voltage swing without increasing a supply voltage of the oscillator. The dual-mode oscillators are coupled through multi-phase coupled circuits to form a Mobius loop.

Embodiments can provide individualized controlling of noise injection during startup of a crystal oscillator. In some embodiments, a simple learning block can be placed in parallel to a crystal oscillator circuit to control noise injection during the startup of the crystal oscillator. The learning block can be configured to control the noise injection during the startup of the crystal oscillator by determining whether the crystal oscillator has been stabilized. In some implementations, an adjustment block may be employed to adjust the count determined by the learning block based on one or more characteristics of the crystal oscillator during a startup of the crystal oscillator. In some embodiments, a simple block that creates a negative capacitance can be configured in parallel to the crystal oscillator.

An apparatus is disclosed for injecting a frequency-modulated signal into a receiver. In an example aspect, the apparatus includes a receiver, a local oscillator circuit, and an injection circuit. The receiver comprises a signal propagation path. The local oscillator circuit is configured to generate a frequency-modulated signal. The injection circuit is coupled to the receiver and the local oscillator circuit. The injection circuit is configured to selectively connect the local oscillator circuit to the signal propagation path of the receiver to inject the frequency-modulated signal into the signal propagation path of the receiver. The injection circuit is also configured to disconnect the local oscillator circuit from the signal propagation path of the receiver.

In an exemplary structure, a transformer has a primary side and a secondary side. Output from the primary side is coupled to the secondary side. A first power supply is connected to a center tap of the primary side of the transformer. An oscillator includes a first transistor and a second transistor. The front-gate of the first transistor is connected to the drain of the second transistor and the primary side of the transformer. The front-gate of the second transistor is connected to the drain of the first transistor and the primary side of the transformer. A third transistor is connected to the first transistor and a fourth transistor is connected to the second transistor. The third and fourth transistors inject a desired frequency to the oscillator. A voltage source is connected to the back-gate of the first transistor and the back-gate of the second transistor.