Patent ID: 8675778
Filing Date: 2014-03-18
Classification: H04L

Abstract:
1. A carrier recovery circuit adapted to a demodulation circuit according to a quasi-coherent detection method, said carrier recovery circuit comprising: a phase rotator that rotates a phase of a baseband signal detected from a received signal; a phase error detector that detects a phase error included in the baseband signal with the rotated phase; an amplitude error detector that detects an amplitude error included in the baseband signal with the rotated phase; a loop filter that eliminates a high-frequency component from the phase error; a loop filter controller that controls a bandwidth of the loop filter based on the phase error and the amplitude error; and a phase rotation controller that controls the phase rotator based on the phase error eliminating its high-frequency component, wherein the loop filter controller expands the bandwidth of the loop filter when a difference between the phase error and the amplitude error is greater than a predetermined threshold, whilst the loop filter controller reduces the bandwidth of the loop filter upon determining that the amplitude error decreases due to a reduction of the bandwidth of the loop filter, wherein the loop filter controller determines that the amplitude error decreases due to a reduction of the bandwidth of the loop filter when a difference between the amplitude error and a minimum value among previous amplitude errors is greater than the predetermined threshold.