Method and apparatus for determining a constant gain of a variable oscillator

A method and apparatus for implementing a constant gain in a digitally-controlled variable oscillator (DCO) 16 where the frequency of the DCO 16 is controlled via binary-weighted control signals. The frequency of the DCO 16 is modulated via arithmetic increments or decrements to the binary-weighted DCO control signals. The magnitude of the arithmetic increments and decrements defines the gain of the DCO. To maintain a constant gain, regardless of operating point or environment, a phase gain register 15 bit-shifts a current DCO control value by a predefined number of bit positions, thereby determining a phase gain value. The phase gain value defines the magnitude of an arithmetic increment or decrement of the current DCO control value, used to determine the next DCO control value. Since the phase gain register 15 uses a bit-shifted version of the current value of the DCO control, the gain value dynamically tracks all updates to the DCO control value, thereby implementing a constant gain in the DCO 16.