| 摘要 |
A digital modulator having a pulse shaping filter which generates and accumulates impulse responses including prior impulse responses and posterior impulse responses to perform a Root-Nyquist raised cosine filtering. The pulse shaping filter includes a dummy accumulation data memory storing dummy accumulation values of prior impulse responses required for initial data transmission. When several initial impulse responses are to be transmitted, for example, on power-up, the impulse responses corresponding to input digital data are generated and added to the dummy accumulation values of prior impulse responses. After the initial transmission, the impulse responses corresponding to input digital data are generated and transmitted without the help of the dummy accumulation values.
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