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| Computers Forum Index » Computer - DSP » symmetric and asymmetric filters....... |
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| fisico32... |
 Posted: Wed Oct 28, 2009 5:16 am |
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Guest
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Hello Forum,
the Fourier transform of a signal breaks down the signal into positive and
negative imaginary exponentials (i.e. involving positive and negative
frequencies).
Negative temporal frequencies are just an artifact deriving from the use
of complex exponentials....
Now, if the signal x(t) is real, the negative frequency part of the
spectrum is totally redundant: |X(w)|=|X(-w)|, and the phase
theta(w)=-theta(-w). The power spectrum is symmetric.
If a system has a transfer function H(w) whose power spectrum is not
symmetric, what does it means physically?
For example, if a sinusoid of frequency w_0 enters the system, how do we
interpret the gain and phase at the positive and negative frequency w_0?
Any example? What happens to that sinusoidal signal?
In practice, what is an asymmetric filter? Is it physical?
thanks
fisico32 |
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| Rune Allnor... |
| Posted: Wed Oct 28, 2009 6:28 am |
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Guest
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On 28 Okt, 02:54, "fisico32" <marcoscipio... at (no spam) gmail.com> wrote:
Quote: In practice, what is an asymmetric filter? Is it physical?
Forget about 'physical.' Asymmetric filters exist - are
'physical' - for both quadrature temporal signals and
spatial signals. However, these filters are not necessarily
*intuitively* easy to understand.
Rune |
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