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DSP Filters and slopes?
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<blockquote data-quote="Matt Errend" data-source="post: 27131" data-attributes="member: 618"><p>Re: DSP Filters and slopes?</p><p></p><p>I'm no expert on this topic, but the general rule is that because DSP working in real time, there is no way to "see" future signal and determine what is coming in and just instantly decide where to put it. Because of this fundamental flaw of physics <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" />p), any filter will have a penalty in time. We see this in the form of phase shift, and as you increase the slope of a filter, the greater the shift. </p><p></p><p>Brick wall filters as you describe exist, but they also exhibit the greatest penalty in phase shift. This can be compensated for by aligning the high pass filter with the low pass in time so the phase shift is minimized or negated completely, but you are still left with an overall delay. The lower the frequency of your filter, the greater the delay and the more processing power required. </p><p></p><p>As a note of interest: 8th order (48dB/oct) filters have been constructed using completely passive parts, but they are terribly complicated and have the greatest insertion loss so they're very uncommon.</p></blockquote><p></p>
[QUOTE="Matt Errend, post: 27131, member: 618"] Re: DSP Filters and slopes? I'm no expert on this topic, but the general rule is that because DSP working in real time, there is no way to "see" future signal and determine what is coming in and just instantly decide where to put it. Because of this fundamental flaw of physics (:p), any filter will have a penalty in time. We see this in the form of phase shift, and as you increase the slope of a filter, the greater the shift. Brick wall filters as you describe exist, but they also exhibit the greatest penalty in phase shift. This can be compensated for by aligning the high pass filter with the low pass in time so the phase shift is minimized or negated completely, but you are still left with an overall delay. The lower the frequency of your filter, the greater the delay and the more processing power required. As a note of interest: 8th order (48dB/oct) filters have been constructed using completely passive parts, but they are terribly complicated and have the greatest insertion loss so they're very uncommon. [/QUOTE]
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