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pls can any body make me understand difference between power signals & Energy signals. why r random signals called power signals. This message was sent using the Comp.DSP web interface on www.DSPRelated.com

geeez i wish the chat-room lingo would stay in the chat room. in article V...@giganews.com, shikha at s...@yahoo.co.in wrote on 04/16/2005 09:01: > > pls can any body make me understand difference between power signals & > Energy signals. a finite energy signal: +inf total energy = integral{ x(t)^2 dt} < infinity -inf a finite power signal: +T/2 average power = lim 1/T integral{ x(t)^2 dt} < infinity T->inf -T/2 > why r random signals called power signals. because, like a sine wave, if they are left turned on forever, they will deliver an infinite amount of energy. but their average power is finite. -- r b-j r...@audioimagination.com "Imagination is more important than knowledge."

shikha wrote: > pls can any body make me understand difference between power signals & > Energy signals. > why r random signals called power signals. Trying to make it easy: An energy signal has a finite energy. Signals of a limited length also carry a finite energy, and so they are energy signals. A signal that decays exponentially, for example, also has a finite energy. A power signal is not limited in time (it is *always* on, from the Big-Bang to Judgement Day and beyond), and has an *infinite* energy. Since an infinite energy has no meaning for us, then we use the energy per unit of time, i.e., power. Examples: A square pulse is an energy signal. A square wave of infinite length is a power signal.

"Jerry Avins" <j...@ieee.org> wrote in message news:i...@rcn.net... > Fred Marshall wrote: > > >> A signal is an "energy signal" if, and only if, it has nonzero but finite >> energy for all time 0<Ex<inf: > > ... > >> A signal is a "power signal" if, and only if, it has finite but nonzero >> power for all time 0 < Px < inf: > > Hunh? again. A sinusoid fits neither of those verbal descriptions. > Jerry, First off, these were all "quotes" ...... and I was questioning the whole thing from the get go. Second, why doesn't a sinusoid have finite but nonzero power for all time? er.... if I know what that even means! Again, if power is energy per unit time then finite for all time (in chunks of time) seems OK to me. Fred Fred

Jerry Avins <j...@ieee.org> writes: > Fred Marshall wrote: > > ... > > > - An energy signal has zero average power. A power signal has > > infinite average energy. > > > Huh? Power goes with the square of magnitude (into a resistive > load). It is a positive number for all non-zero magnitudes. To have > zero average power, a signal must be brief and averaged over all time, > or everywhere zero. This is correct, Jerry, as I understand it. Any finite-temporal-extent signal is considered a finite-energy, zero-power signal because of the first reason you stated. -- Randy Yates Sony Ericsson Mobile Communications Research Triangle Park, NC, USA r...@sonyericsson.com, 919-472-1124

Jerry Avins <j...@ieee.org> writes: > Fred Marshall wrote: > > > > A signal is an "energy signal" if, and only if, it has nonzero but > > finite energy for all time 0<Ex<inf: > > > ... > > > A signal is a "power signal" if, and only if, it has finite but > > nonzero power for all time 0 < Px < inf: > > > Hunh? again. A sinusoid fits neither of those verbal descriptions. Why don't you think a sinusoid has finite but non-zero power? When Fred stated "... for all time..." I'm assuming he means "when averaged over all time." -- Randy Yates Sony Ericsson Mobile Communications Research Triangle Park, NC, USA r...@sonyericsson.com, 919-472-1124