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E7H09

PRACTICAL CIRCUITS · Oscillators and signal sources: types of oscillators; synthesizers and phase-locked loops; direct digital synthesizers; stabilizing thermal drift; microphonics; high-accuracy oscillators

E7H09E7H →

What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converter, and a low-pass anti-alias filter?

  1. AA direct digital synthesizer
  2. BA hybrid synthesizer
  3. CA phase-locked loop synthesizer
  4. DA direct conversion synthesizer
Why A direct digital synthesizer builds the waveform numerically: a phase accumulator adds a tuning word to a running phase value on each clock tick, the accumulated phase indexes a sine lookup table, a DAC turns those samples into an analog staircase, and a low-pass anti-alias filter smooths it into a clean sine wave. Output frequency is set by the tuning word and the reference clock, so frequency changes are instant and extremely fine in resolution. The blocks named in the question are exactly the DDS signal chain.
Watch out A phase-locked loop synthesizer is the other common approach, but it works with a VCO, phase detector, loop filter and programmable divider, not a lookup table and DAC. Direct conversion is a receiver architecture, not a synthesizer type.
Phase accumulator plus lookup table plus DAC equals DDS: digital numbers in, sine wave out.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
← E7H08 All of E7H E7H10 →

The rest of E7H

  1. E7H01 What are three common oscillator circuits?
  2. E7H02 What is a microphonic?
  3. E7H03 What is a phase-locked loop?
  4. E7H04 How is positive feedback supplied in a Colpitts oscillator?
  5. E7H05 How is positive feedback supplied in a Pierce oscillator?
  6. E7H06 Which of these functions can be performed by a phase-locked loop?
  7. E7H07 How can an oscillator's microphonic responses be reduced?
  8. E7H08 Which of the following components can be used to reduce thermal drift in crystal oscillators?
  9. E7H09 What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converte…
  10. E7H10 What information is contained in the lookup table of a direct digital synthesizer (DDS)?
  11. E7H11 What are the major spectral impurity components of direct digital synthesizers?
  12. E7H12 Which of the following ensures that a crystal oscillator operates on the frequency specified by the crystal m…
  13. E7H13 Which of the following is a technique for providing highly accurate and stable oscillators needed for microwa…
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