Direct Digital Synthesizer

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Direct Digital Synthesizer

• STUDENT Tsung-Han Tu
• SN M9720112

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Direct Digital Synthesizer(1/2)

• The DDS is constructed by a ROM with many samples
  of a sine wave stored in it.
• The DDS produces sinusoidal signal. The frequency
  of the output signal for a n-bit system is
  determined by

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Direct Digital Synthesizer(2/2)
Fig. 1 Block diagram of a DDS system.
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Multiple frequencies from a single DDS(1/3)

• Instead of using only one frequency setting
  word (FSW) three of them are employed.
• The formula, which gives the output frequency.

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Multiple frequencies from a single DDS(2/3)

• Two non-consecutive outputs of the line decoder
  are used for the generation of the 57 KHz signal.

Fig. 4 Block diagram of a multiplexed DDS system.
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FPGA
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Multiple frequencies from a single DDS(3/3)

• Waveforms produced at the three outputs of the
  multiplexed DDS.

Fig. 5 From top to bottom the 19KHz, 57KHz and
38KHz waveforms.
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• Thanks