| 摘要 |
PURPOSE:To obtain modulating function by a general microprocessor by changing the number of times of sampling in one baud rate and accessing a table by sampling data and data to be modulated to read out the contents of the table. CONSTITUTION:As the reading timing of the table, 7,200Hz sampling frequency corresponding to 4 times the 1,800Hz modulation carrier frequency is used. In a ROM1, data indicating the absolute value of a modulated signal as a digital value in a table are alternately and repeatedly sampled by 4-5 times in each one baud. Sampling signals outputted from gates G1-G9 are outputted as a 4-bit signal through a sample counter 12. On the other hand, RAMs 3-10 store the X and Y components of the past four symbol components as the data to be modulated. These sampling data and the data to be modulated are accessed to the ROM1 is multiplied by an integrating algorithmic unit 14 and the multiplied result is outputted through a D/A converter 15.
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