| 摘要 |
PURPOSE: A digital modulator in a communication system is provided to form a new pulse shaping filter by mathematically combining a pulse shaping filter function and a vector modulator function for generating and mixing a sine/cosine wave. CONSTITUTION: In a digital convert, a pulse shaping filter(10-1) for 1 channel has a new tap coefficient output by multiplying a cosine wave value provided into a mixer for 1 channel with a tap coefficient of a previous pulse shaping filter for 1 channel. The pulse shaping filter for 1 channel concurrently carries out a vector modulator function and a pulse shaping filter function for the 1 channel data of an in-phase component input by varying the tap coefficient periodically. A pulse shaping filter(10-2) for Q channel has a new tap coefficient output by multiplying a sine wave value provided into a mixer for Q channel with a tap coefficient of a previous pulse shaping filter for Q channel. The pulse shaping filter for Q channel concurrently carries out a vector modulator function and a shaping filter function for a Q channel data of an orthogonal component input by varying the tap coefficient periodically. An adder(20) adds the 1 channel data from the pulse shaping filter for 1 channel and the Q channel data from the pulse shaping filter for Q channel.
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