Patent ID: 7130360

Claim:
A receiving apparatus of a digital communication system, comprising: A/D converting means for performing an over-sampling process to convert an analog signal inputted from a transmitter to a digital signal and outputting over-sampled symbols; sample classifying means for classifying the over-sampled symbols of which phases are the same based on a phase of the over-sampled symbol in a symbol interval and outputting classified symbols; integrating means for accumulating values of the classified symbols by adding each value of the classified symbols for a predetermined time and outputting integrated values, the integrating means includes a plurality of complex envelop calculators for calculating absolute values of the classified symbols of an I-channel and a Q-channel in every symbol interval and outputting the absolute values; symbol synchronizing means for selecting a point of symbol synchronization based on the integrated values and the classified symbols and outputting a first value, which is a maximal value of the point of symbol synchronization; phase estimating means for estimating a phase error based on the first value and outputting a second value of an estimated phase error; frequency estimating means for estimating a frequency error based on the second value and outputting a third value of an estimated frequency error; and digital demodulating means for performing a demodulation by using the first value, the second value and the third.