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发表于 2010-6-18 14:20:38
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iirnotch的用法如下:
iirnotch -
Second-order IIR notch filter
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Syntax
[num,den] = iirnotch(w0,bw)
[num,den] = iirnotch(w0,bw,ab)
Description
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[num,den] = iirnotch(w0,bw) turns a digital notching filter with the notch located at w0, and with the bandwidth at the -3 dB point set to bw. To design the filter, w0 must meet the condition 0.0 w0 1.0, where 1.0 corresponds to π adians per sample in the frequency range.
The quality factor (Q factor) q for the filter is related to the filter bandwidth by q w0/bw where ω0 is w0, the frequency to remove from the signal.
[num,den] = iirnotch(w0,bw,ab) returns a digital notching filter whose bandwidth, bw, is specified at a level of -ab decibels. Including the optional input argument ab lets you specify the magnitude response bandwidth at a level that is not the default -3 dB point, such as -6 dB or 0 dB.
Examples
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Design and plot an IIR notch filter that removes a 60 Hz tone (f0) from a signal at 300 Hz (fs). For this example, set the Q factor for the filter to 35 and use it to specify the filter bandwidth:
wo = 60/(300/2); |
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