Hi, I designed a filter using remezord function. When I filtered the input first and downsampled later, the filter works fine. out2a=filter(h1,1,out1a); out2b=downsample(out2a,4); But when I downsampled first and then fitlered it later the output is incorrect. out2a=downsample(out1a,4); out2b=filter(h1,1,out2a); Any help is highly appreciated. Thanks, EngGan |
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filter and downsample
Started by ●June 30, 2003
Reply by ●July 1, 20032003-07-01
The result is as expected. For making things very clear, ask the question why do u do the filtering? The filtering bandlimits the signal and then u downsample-----> Results should be OK When u downsample first there will be folding effect and the resultant signal is corrupted by the reflection of frequencies outside our bandlimit. From here on you are dealing with a corrupted signal. Hope it's clear. ----- Original Message ----- From: "egan_nc" <> To: <> Sent: Monday, June 30, 2003 8:09 PM Subject: [matlab] filter and downsample > Hi, > I designed a filter using remezord function. When I filtered the > input first and downsampled later, the filter works fine. > out2a=filter(h1,1,out1a); > out2b=downsample(out2a,4); > But when I downsampled first and then fitlered it later the output is > incorrect. > out2a=downsample(out1a,4); > out2b=filter(h1,1,out2a); > Any help is highly appreciated. > Thanks, > EngGan > _____________________________________ > Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. > > _____________________________________ > About this discussion group: > > To Join: > > To Post: > > To Leave: > > Archives: http://www.yahoogroups.com/group/matlab > > More DSP-Related Groups: http://www.dsprelated.com/groups.php3 > > ">http://docs.yahoo.com/info/terms/ > +++++++++++++++++++++++++++++++ Disclaimer +++++++++++++++++++++++++++++++++++++++ This e-mail may contain privileged and confidential information and is intended only for the use of the specific individual(s) to whom it is addressed. If you are not an intended recipient of this e-mail, you are hereby notified that any unauthorized use, dissemination or copying of this e-mail or the information contained in it or attached to it is strictly prohibited. If you have received this e-mail in error, please delete it and immediately notify the undersigned by reply e-mail. Hellosoft India Pvt. Ltd. www.hellosoft.com +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
Reply by ●July 1, 20032003-07-01
Filtering and down sampling are not commutative. Regards, Navan --- egan_nc <> wrote: > Hi, > I designed a filter using remezord function. When I > filtered the > input first and downsampled later, the filter works > fine. > out2a=filter(h1,1,out1a); > out2b=downsample(out2a,4); > But when I downsampled first and then fitlered it > later the output is > incorrect. > out2a=downsample(out1a,4); > out2b=filter(h1,1,out2a); > Any help is highly appreciated. > Thanks, > EngGan __________________________________ |