Min carrier frequency in Amp Mod.

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Discussion Overview

The discussion revolves around determining the minimum usable carrier frequency in a Double Sideband Suppressed Carrier (DSB-SC) system, given a message signal limited to B Hz. Participants explore concepts related to Nyquist theory and the implications of sideband frequencies.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how to apply Nyquist theory to the problem, indicating uncertainty about its relevance.
  • Another participant suggests that the carrier frequency should not allow any sideband frequency to be 0 Hz or less.
  • A different participant argues that a sideband could only have a bandwidth of 0 Hz or less if the carrier frequency is less than the message frequency, applying Nyquist theory to conclude that the carrier frequency must be at least twice that of the message frequency, though they express uncertainty about this conclusion.
  • Further clarification is provided that the lower sideband is assumed to be a spot frequency with zero bandwidth, challenging the notion of bandwidth in this context.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between carrier frequency and sideband frequencies, with no consensus reached on the minimum carrier frequency requirement or the application of Nyquist theory.

Contextual Notes

There are unresolved assumptions regarding the definitions of bandwidth and the implications of sideband frequencies in relation to carrier frequency.

scubaman
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Homework Statement



Given a DSB -SC system, with a message limited to B Hz, what is the minimum usable value of ωc or f0 (carrier frequency)

Homework Equations



Nyquist theory? Not sure how to apply.

The Attempt at a Solution



Only attempt has been through research.
 
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Hint: we don't want any sideband frequency of 0Hz or less.
 
What does this have to do with sidebands? A sideband could only have a bandwidth of 0Hz or less if Wc was actually less than Wm, no? I applied the nyquist theory (sampling) to this, and concluded that the carrier frequency must be at least twice that of the message frequency. Not sure if this is right though.
 
scubaman said:
What does this have to do with sidebands? A sideband could only have a bandwidth of 0Hz or less if Wc was actually less than Wm, no?

You're getting very warm.

BTW the lower sideband does not "have a bandwidth". It's assumed to be a spot frequency with zero bandwidth.
 

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