Patent ID: 7711073

Claim:
A method for determining the frequency of a received signal for demodulating received signal values (P 1 , P 2 ) in the complex phase space (I, Q) of a modulation technique wherein for the frequency determination the received signal values (P 1 , P 2 ) are compared with symbols (S 1 , S 2 ) at nominal positions in the complex signal space, the method comprising: converting a first received signal value P 1 and a second received signal value P 2 of a quadrature amplitude modulated signal from Cartesian coordinate space to polar coordinate space to provide a first radial component and a first angle component indicative of the first received signal value P 1 and a second radial component and a second angle component indicative of the second received signal value P 2 ; determining the difference between the first angle component and the second angle component and providing a difference signal indicative thereof; comparing the difference signal against a plurality of nominal angles associated with the modulation technique and determining which of the plurality of nominal angles is closest to the difference signal as a measure for a frequency offset (Δf) and providing a first control signal indicative thereof; and comparing an equalized signal (S) and an estimated symbol (Se) to provide an angle error signal; controlling a voltage controlled oscillator using the first control signal when the value of the first control signal is greater than a threshold value, otherwise controlling the voltage controlled oscillator using a second control signal indicative of the angle error signal; where the converting, the determining, the comparing the received signal values, comparing the difference signal and the controlling are implemented in a circuit arrangement configured for demodulation.