AUTOMATIC FREQUENCY CONTROL CIRCUIT AND FREQUENCY OFFSET CORRECTION METHOD USED IN THE CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide an automatic frequency control circuit which reduces an influence of the error of frequency offset to correct the frequency offset with a high precision. SOLUTION: AΔθestimating part 8 obtains two phase deviationsΔθ1 andΔθ2 per bit from a reception signal. Phase deviationsΔθ1 andΔθ2 per bit are integrated with precedingθ+(n-1)Δθat timings to respective channel bit rates by addition parts 1 and 2 and F/Fs 3 and 4. A selector selects one of integrated signalsθ+nΔθ1 andθ+mΔθ2 in accordance with a selection signal SEL. A frequency conversion part 6 subjects selectedθ+nΔθto frequency conversion to output cos(θ+nΔθ) and sin(θ+nΔθ). A complex multiplication part 7 performs complex multiplication of cos(θ+nΔθ), sin(θ+nΔθ), and reception signals I and Q to correct the frequency offset.