Question
What are the major spectral impurity components of direct digital synthesizers?
Answer Options
- A) Broadband noise
- B) Digital conversion noise
- C) Spurious signals at discrete frequencies
- D) Harmonics of the local oscillator
Correct Answer: C
Explanation
Direct Digital Synthesizers (\text{DDS}) are celebrated for their speed and fine-tuning resolution, but they suffer from a specific type of signal degradation unique to their digital architecture. This degradation is a form of phase noise or jitter caused by the quantization of the signal.
The major spectral impurity components of \text{DDS} are spurious signals at discrete frequencies, often referred to as ‘spurs.’ These unwanted signals are generated by phase and amplitude errors caused by the finite number of bits used by the phase accumulator and the \text{DAC} in the synthesis process. While highly predictable, these spurs can require careful analog filtering to suppress before transmission.
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