DIGITAL TRANSMITTER

摘要

PROBLEM TO BE SOLVED: To realize an OFDM transmission system that can always detect synchronization by accurately estimating a SWEEP symbol start position even under any transmission state without being affected by presence/absence of a reflecting wave or a noise component. SOLUTION: A data transmitter employing an orthogonal frequency division multiplex modulation system revises a threshold value to detect an end part of a non-signal period used to detect frame synchronization for each prescribed period depending on the transmission state, applies trough modulation to main wave when the CN is a prescribed value or over so as to reduce a time required for complete synchronization and aims first at establishing of the synchronization when the CN is low on the other hand thereby realizing a normal synchronization operation to the main wave in a short time under wider condition.