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bhq
Joined: 11 Jun 2008
Posts: 55
Helped: 4
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 02 Jul 2008 15:36 IIR Filter could be causal or always non causal |
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I want to know that Is IIR filter is always non causal. if not than please send me an example of IIR Filter in difference equation that is causal.
Please think about
y(n) = y(n-1) + x(n-1) + 2*x(n)
Is the above system is causal or non causal?
Is the system is IIR or not ?
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nalino
Joined: 11 Dec 2003
Posts: 311
Helped: 4
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| 04 Jul 2008 17:19 IIR Filter could be causal or always non causal |
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this is a causal system as y(n) only relies on it's past values y(n-1) and x's present and past values...transfer function is
y(n) = y(n-1) +2*x(n) + x(n-1)
Y(z) = Y(z)*z^-1 + 2*X(z) + X(z)*z^-1
H(z) = Y(z)/X(z) = (2+z^-1)/(1-z^-1)
=> 1st order low-pass filter..
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xulfee
Joined: 27 May 2008
Posts: 150
Helped: 17
Location: Pakistan
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| 08 Aug 2008 8:37 IIR Filter could be causal or always non causal |
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| this system is causal the example u given
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premkiran
Joined: 16 Mar 2007
Posts: 7
Helped: 1
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| 09 Aug 2008 12:56 Re: IIR Filter could be causal or always non causal |
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The filter equation , written by you, is a causal iir filter.
Only the required specifications in designing a filter , can drive you either to causal/non causal filer equations.
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