Patent ID: 7751503

Claim:
A method of carrier synchronisation, comprising: determining a phase difference between a local oscillator signal and a carrier signal of a received signal by performing a phase detection function P(t) such that the value of P(t) at periodic instants indicates the phase difference θ between the carrier signal of the received signal R(t) and at least one of first and second local oscillator signals, wherein P ⁡ ( t ) = { tan - 1 ⁡ ( X ⁡ ( t ) Y ⁡ ( t ) ) - sgn ⁡ ( X ⁡ ( t ) · Y ⁡ ( t ) ) · π 4 for ⁢ ⁢ Y ⁡ ( t ) ≠ 0 π 4 · sgn ⁡ ( X ⁡ ( t ) ) for ⁢ ⁢ Y ⁡ ( t ) = 0 where X(t) is derived from the received signal R(t) mixed with a first local oscillator signal, and Y(t) is derived from the received signal R(t) mixed with a second local oscillator signal; determining a frequency offset estimate from a rate of change of the phase difference between the local oscillator signal and the carrier signal of the received signal; and adjusting a frequency of the local oscillator signal by the frequency offset estimate.