Abstract: The present invention relates to a method and an apparatus for spread spectrum modulation and demodulation using a special spread spectrum sequence, characterized in that Golay complementary codes are modulated onto orthogonal channels such that a corresponding complex complementary code is obtained. The signal spread by such complex complementary code has a low peak-to-average power ratio, a sound self-correlation property and cross-correlation property, which can well solve the problem of multi-access interference such that the communication performance of the entire system is improved.

Abstract: The present invention relates to an apparatus for accurately detecting a mains phase. The apparatus is constructed with a zero-crossing detector, a digital phase detector, a digital loop filter, and a digital controlled oscillator (DCO) of a direct digital synthesized (DDS) manner. The present apparatus employs an all-digital loop architecture and a high sampling clock to recover a signal with a phase orthogonal with the mains signal and a frequency the same as the mains signal. And jitters in the recovered signal are less than 10 us. The present apparatus is capable of implementing signal tracking of a zero frequency error and a zero phase in a wide range, and can provide a detection result of excellent performance for the power line carrier communication, mains frequency detection, etc.