| 摘要 |
PURPOSE:To quicken the synchronization between a sub data signal and a main data signal at a demodulator side by providing a preamble period in which no phase modulation is caused by the sub data signal so as to avoid adverse effect onto a carrier locking time at the demodulator side and to send a unique word. CONSTITUTION:A sub data transmission signal generating circuit 1 generates a sub data transmission control signal D2 resulting from applying time division multiplex to a preamble signal whose value is 0, a unique word and a sub data signal D1. A ROM 2 and a D/A converter 4 output an in-phase component amplitude of a composite modulation wave resulting from phase modulating a modulation wave subject to 16-value orthogonal amplitude modulation of a carrier by main data signal X1, X2, Y1, Y2 with a sub data transmission control signal D2, and a ROM 3 and a D/A converter 5 output similarly an orthogonal component amplitude. A carrier outputted from a carrier oscillator 8 is orthogonal modulated by outputs of the D/A converters 4, 5 to obtain a composite modulation wave M. |
