| 摘要 |
PURPOSE:To modulate a signal whose transmission speed is fast by means of digital signal processing by selecting a carrier frequency in the vicinity of a base band signal band to suppress the signal processing speed for the digital signal processing to be low. CONSTITUTION:A ROM and a counter is used to generate a carrier signal. Then amplitude information data resulting from m-sampling of one period of Ich and Qch carrier signals are stored in each ROM. Then the carrier signal is generated by reading sequentially the waveform information from each ROM by using an m-adic counter 6. In this case, the m-adic counter use clock signals have been inputted conventionally independently of an input signal. In this embodiment, clock signals obtained by multiplying the clock signals synchronously with the input signal through the use of an m.n multiplier circuit are used for the m-adic counter use clock signals. Thus, a carrier frequency fc satisfying equation is obtained by modulating a signal filtered through sampling of a multiple of X with respect to a base band signal whose period is T by means of digital signal processing. |
