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You cannot convolve the two filters because their input rates are not equal. You can: 1. Multiply the real-frequency responses together, H12(f) = H1(f)*H2(f) = H1(w*1.5e6/2/pi)*H2(w*96e3/2/pi); or 2. Upsample h2 (the time-domain impulse response) from 96kHz to 1.5MHz, then convolve h12 = conv(h1,h2), then use freqz with 1.5MHz as the sample rate. For #1, f is the actual hertz, and w is the "digital angular frequency", i.e., w at Nyquist = pi. Sincerely, Glen Ragan -----Original Message----- From: egan_nc [mailto:] Sent: Tuesday, August 05, 2003 3:34 PM To: Subject: [matlab] sampling freq for combined filter Hi, Can anybody please tell me how to set up the sampling freq for a combined filters. The sampling freq for the input signal to the first filter h1 is 1.5Mhz, the output of the first filter is then downsampled to 96khz and feed into the second filter h2. h12 is the convolution of h1*h2. To plot the freq response of h12 with freqz, what is the sampling freq to use? freqz(h12,1,2048,'whole','fs?????') Thank you, EngGan <http://rd.yahoo.com/M%1812.3170658.4537139.1261774/D=egroupweb/S05 083376:HM/A93353/R=0/SIGt71ok4g/*http://www.netflix.com/Default?mq so`178294&partid170658> click here <http://us.adserver.yahoo.com/l?M%1812.3170658.4537139.1261774/D=egrou pmail/S=:HM/A93353/rand4230221> _____________________________________ 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/> . |