Difficulty - Signals and Systems

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Discussion Overview

The discussion revolves around the concept of characteristic modes in signals and systems, specifically focusing on the interpretation of a statement regarding how signals are sustained by a system. Participants seek clarification on the meaning and implications of this concept.

Discussion Character

  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Salil expresses confusion about a statement regarding signals and characteristic modes, asking for help in understanding it.
  • Fleem explains that a characteristic mode refers to a natural oscillation pattern of a system, illustrating the concept with an example of pushing a swing at its natural frequency.
  • Fleem notes that energy added at non-characteristic frequencies will not be absorbed over time, suggesting that the term "sustained" may not apply if energy is lost to resistive forces.
  • Another participant, unnamed, questions the clarity of the original quote and suggests it may lack context or be poorly translated.
  • Salil acknowledges Fleem's explanation as helpful and reflects on the tendency to overcomplicate simple concepts.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of the original statement, with some expressing uncertainty about its meaning and others providing explanations that may or may not align.

Contextual Notes

The discussion highlights the need for context in understanding technical statements, as well as the potential for misinterpretation when quotes are not fully provided.

salil87
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Hi
In my notes I came across the following sentences:-
Any signal consisting of the system's characteristic mode is sustained by the system on its own. The system offers no obstacle to this signal.
Not getting what it means. Please, a little help needed. :-)

Thanks
salil
 
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A characteristic mode is simply a natural oscillation pattern the system possesses. If you add energy to a system which is NOT in one of the system's natural oscillation patterns, then that energy will not be continually absorbed over time. For example, if you are pushing someone on a swing and the frequency you are pushing does not match the natural frequency of the swing, then you won't make any notable progress getting the swing going. But if you add energy at the 'characteristic mode' of the swing (the right spectrum of frequencies), then it will be continually absorbed causing the swing amplitude to increase. If there is an energy waster (like an electrical resistor, brake, wind resistance, etc.) in the system then I'm not sure I'd use the word "sustained" as they do in the statement, but I think the general point is that that energy will be absorbed by the system.
 
I have no idea what that is supposed to mean, out of context. Can you give a longer quote? Is the quote a computer translation from a different language?

Fleem's answer might be correct, or it might not.
 
Sorry for the short Description. Guess it happens when I'm in tension. :-) But Thanks a lot Fleem ... your explanation helped a lot. Your Swing example rocks. Sometimes I think of such simple things in such complicated ways. Thanks a lot again. :-)
Thanks
Salil
 

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