Freescale Semiconductor,inc.

Walt Kehler

Nihal J Godambe

A level detector ( ) and corresponding method detects ( ) whether an output signal level of a VCO ( ) is within a window bounded by minimum and maximum thresholds. When the output signal level is not within the window, a loop-control element ( ) closes ( ) an AGC loop of the VCO and controls the gain of the VCO with a gain-control signal that tracks an AGC bias signal. When the output signal level is within the window, the loop-control element opens ( ) the AGC loop and controls the gain with a fixed bias signal derived from the AGC bias signal at the time the AGC loop is opened.

Method and apparatus for controlling a voltage controlled oscillator

A rectifier ( ) rectifies ( ) an output signal of a VCO ( ) to produce an envelope signal proportional to an amplitude of the output signal. An integrator ( ) integrates ( ) the envelope signal to produce a comparison signal, such that, in response to a change in the envelope signal, during a first mode of operation of the VCO, the comparison signal is allowed to change at a first rate, and, during a second mode of operation of the VCO, the comparison signal is allowed to change at a second rate different from the first rate. A comparator ( ) compares ( ) the comparison signal with a reference signal ( ) to produce a bias signal, and controls ( ) a gain of the VCO with the bias signal.

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Walt Kehler