DEMODULATOR FOR ORTHOGONAL MODULATION SIGNAL

• Main Author: ARITA HISASHI
• Format: Patent
• Language: English
• Published: 04.03.1992
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PICTORIAL COMMUNICATION, e.g. TELEVISION; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

PURPOSE:To attain optimum demodulation of data automatically with simple initial phase adjustment even in the case of multi-value modulation or in the case of deteriorated C/N by detecting the distribution of a change point of data so as to control the phase of a carrier signal. CONSTITUTION:An inputted orthogonal modulation signal is subject to synchronization detection by detectors 1i, 1q by using two orthogonal carrier signals as above. The amplitude level is discriminated from detection output signals Ai, Aq having an N-value amplitude level being outputs of the detectors 1i, 1q A pules signal C, an original oscillation clock signal D and a clock signal E are inputted to a change point detector 10 detecting data change point distribution, the phase of the clock signal E is divided equally into 1/M by using the original oscillation clock signal D based on the clock signal E to detect in which phase timing the pulse signal C is inputted and the information of the phase narrowing the distribution of the pulse signal C is outputted to a variable phase shifter 3 as a change point detection signal F. The variable phase shifter 3 shifts the phase of a carrier signal according to the information of the change point detection signal F.