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G7C10

PRACTICAL CIRCUITS · - Transceiver design; filters; oscillators; digital signal processing (DSP)

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What is an advantage of using I-Q modulation with software-defined radios (SDRs)?

  1. AThe need for high resolution analog-to-digital converters is eliminated
  2. BAll types of modulation can be created with appropriate processing
  3. CMinimum detectible signal level is reduced
  4. DAutomatic conversion of the signal from digital to analog
Why I-Q modulation splits a signal into two components 90 degrees apart, in-phase (I) and quadrature (Q). Any signal can be described by its amplitude and phase at each instant, and any amplitude/phase pair can be built from the right combination of I and Q values. Because software can compute those I and Q streams however it likes, an SDR can generate or decode AM, FM, SSB, CW, PSK, or any other mode with nothing but a change in the processing code.
Watch out The choice about eliminating high resolution A/D converters has it backwards: good dynamic range in an SDR still depends heavily on the resolution of the converters, and I-Q sampling does not change that.
I and Q give you amplitude and phase, and amplitude plus phase equals every mode.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of G7C

  1. G7C01 What circuit is used to select one of the sidebands from a balanced modulator?
  2. G7C02 What output is produced by a balanced modulator?
  3. G7C03 What is one reason to use an impedance matching transformer at a transmitter output?
  4. G7C04 How is a product detector used?
  5. G7C05 Which of the following is characteristic of a direct digital synthesizer (DDS)?
  6. G7C06 Which of the following is an advantage of a digital signal processing (DSP) filter compared to an analog filt…
  7. G7C07 What term specifies a filter's attenuation inside its passband?
  8. G7C08 Which parameter affects receiver sensitivity?
  9. G7C09 What is the phase difference between the I and Q RF signals that software-defined radio (SDR) equipment uses …
  10. G7C10 What is an advantage of using I-Q modulation with software-defined radios (SDRs)?
  11. G7C11 Which of these functions is performed by software in a software-defined radio (SDR)?
  12. G7C12 What is the frequency above which a low-pass filter's output power is less than half the input power?
  13. G7C13 What term specifies a filter's maximum ability to reject signals outside its passband?
  14. G7C14 The bandwidth of a band-pass filter is measured between what two frequencies?
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