Method and Apparatus to control the LC Tank Temperature Null Characteristic in a Highly Stable LC Oscillator

A substantially temperature-independent LC-based oscillator uses bias control techniques. Temperature independence may be achieved by controlling the harmonic frequency content of the output of the oscillator by controlling the amplitude. Amplitude control may be achieved by inserting a control mechanism in the feedback loop of the oscillator.

The present invention generally relates to oscillators which provide a highly stable output frequency across a wide range of temperature variation. Electronic clock generation classically relies on a reference oscillator based on an external crystal that is optionally multiplied and/or divided to generate the required clock. The key specifications of a clock, other than its target frequency, are frequency accuracy and stability. Frequency accuracy is the ability to maintain the target frequency across supply and temperature and is usually represented as drift from the target frequency in percent or parts per million (ppm). Long term stability, is impacted by the close-in phase noise of the oscillator. An oscillator using a high-Q element typically has a low phase noise profile, and thus good frequency stability, and is less sensitive to variations in oscillator amplifier gain, which is dependent on supply and temperature.