Automatic frequency correction

A Frequency Shift Keying receiver comprising:

• a local signal generator for generating a local frequency reference signal and a bitclock signal;
• a receiver front end arranged to receive said local frequency reference signal and a Frequency Shift Keying modulated signal comprising a synchronisation sequence, and to downconvert the Frequency Shift Keying modulated signal using the local frequency reference signal to provide baseband in-phase and quadrature signals;
• a pulse generator coupled to said receiver front end to receive said baseband in-phase and quadrature signals, to generate an in-phase pulse signal comprising pulses aligned with edges of the baseband in-phase and quadrature signals when the baseband in-phase signal leads the baseband quadrature signal, and to generate a quadrature pulse signal comprising pulses aligned with edges of the baseband in-phase and quadrature signals when the baseband quadrature signal leads the baseband in-phase signal;
• and
• a frequency corrector coupled to said pulse generator to receive said in-phase and quadrature pulse signals during receipt of said synchronisation sequence, to compare the in-phase and quadrature pulse signals to a target, and to generate a control signal for controlling the local signal generator in dependence upon the result of the comparison.