Patent ID: 6636571
Filing Date: 2003-10-21
Classification: H03J,H04L

Abstract:
An automatic frequency control circuit comprising:a controllable oscillator for generating a signal having a frequency responsive to an input; circuitry for comparing the output of the controllable oscillator to a carrier frequency; circuitry for adjusting said input to said controllable oscillator, said adjusting circuitry comprising: circuitry for determining real and imaginary components (I and Q) of an angle of rotation (&thgr;) between said carrier frequency and the frequency output by the controllable oscillator, where &thgr;=arctan(Q/I); circuitry for generating an approximation of the angle of rotation (&thgr;â€²), wherein &thgr;â€²=sin (&thgr;)+(1âˆ’cos (&thgr;)) for sin (&thgr;)>0 and &thgr;â€²=sin (&thgr;)âˆ’(1âˆ’cos (&thgr;)) for sin (&thgr;)<0.