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E8A11

SIGNALS AND EMISSIONS · Fourier analysis; RMS measurements; average RF power and peak envelope power (PEP); analog/digital conversion

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Which of the following is a measure of the quality of an analog-to-digital converter?

  1. ATotal harmonic distortion
  2. BPeak envelope power
  3. CReciprocal mixing
  4. DPower factor
Why An analog-to-digital converter is judged by how faithfully its digital output reproduces the input waveform, so the standard figures of merit are distortion and noise numbers: total harmonic distortion, signal-to-noise ratio, SINAD, and effective number of bits. Quantization error and any nonlinearity in the converter's transfer curve create spurious products at harmonics of a pure input tone, and total harmonic distortion sums the power in those harmonics relative to the fundamental. A lower THD figure means the converter's steps track the analog input more linearly.
Watch out Peak envelope power is a transmitter output measurement, reciprocal mixing describes receiver local-oscillator phase noise mixing strong adjacent signals into the passband, and power factor applies to AC circuits with reactive loads. None of them says anything about digitizing accuracy.
ADC quality = how clean the digitized tone is: THD, SNR, SINAD, ENOB. The other three choices belong to transmitters, receivers and AC power.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of E8A

  1. E8A01 What technique shows that a square wave is made up of a sine wave and its odd harmonics?
  2. E8A02 Which of the following is a type of analog-to-digital conversion?
  3. E8A03 Which of the following describes a signal in the time domain?
  4. E8A04 What is "dither" with respect to analog-to-digital converters?
  5. E8A05 What is the benefit of making voltage measurements with a true-RMS calculating meter?
  6. E8A06 What is the approximate ratio of PEP-to-average power in an unprocessed single-sideband phone signal?
  7. E8A07 What determines the PEP-to-average power ratio of an unprocessed single-sideband phone signal?
  8. E8A08 Why are direct or flash conversion analog-to-digital converters used for a software defined radio?
  9. E8A09 How many different input levels can be encoded by an analog-to-digital converter with 8-bit resolution?
  10. E8A10 What is the purpose of a low-pass filter used at the output of a digital-to-analog converter?
  11. E8A11 Which of the following is a measure of the quality of an analog-to-digital converter?
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