# 6th order bessel filter

Started by March 10, 2003
 Hello, I'm a beginner in Matlab. I would like to program a 6th order bessel Low pass filter using matlab. My specifications are as follow : Cutott frequency 8.2MHz and my sampling rate is 52.32 MHz (for DVD purposes). My Code is the following clear all; a=[10395]; wo=1/(8.2e6*2*pi) b=[1*(wo^6) 21*(wo^5) 210*(wo^4) 1260*(wo^3) 4725*(wo^2) 10395*(wo) 10395]; c=tf(a,b) h(c,1/52.32e6,'tustin') bode(h) I do not understand why on my plot,i do not read the same cut off frequency of 8.2 MHZ that i entered in the code. Instead, at -3dB i get 1.5e7. Can someone please tell me what i am doing wrong? Thanks ===== Sylvianne Tameze Sibeliuslaan 93d 5654 CV Eindhoven The Netherlands tel:040-2515881 tel:06-13105124
 You might want to use this: [b,a]sself(6,8.2e6); w=0:100:15e6; freqs(b,a,w); cheers, niranjan - Hello, I'm a beginner in Matlab. I would like to program a 6th order bessel Low pass filter using matlab. My specifications are as follow : Cutott frequency 8.2MHz and my sampling rate is 52.32 MHz (for DVD purposes). My Code is the following clear all; a=[10395]; wo=1/(8.2e6*2*pi) b=[1*(wo^6) 21*(wo^5) 210*(wo^4) 1260*(wo^3) 4725*(wo^2) 10395*(wo) 10395]; c=tf(a,b) h(c,1/52.32e6,'tustin') bode(h) I do not understand why on my plot,i do not read the same cut off frequency of 8.2 MHZ that i entered in the code. Instead, at -3dB i get 1.5e7. Can someone please tell me what i am doing wrong? Thanks ===== Sylvianne Tameze Sibeliuslaan 93d 5654 CV Eindhoven The Netherlands tel:040-2515881 tel:06-13105124
 Hi, Did you try comparing your values with the 'besself' function in signal processing toolbox? Navan --- tameze sylvianne <> wrote: > Hello, > > I'm a beginner in Matlab. I would like to program a > 6th order bessel Low pass filter using matlab. > My specifications are as follow : Cutott frequency > 8.2MHz and my sampling rate is 52.32 MHz (for DVD > purposes). > My Code is the following > > clear all; > a=[10395]; > wo=1/(8.2e6*2*pi) > > b=[1*(wo^6) 21*(wo^5) 210*(wo^4) 1260*(wo^3) > 4725*(wo^2) 10395*(wo) 10395]; > > c=tf(a,b) > h(c,1/52.32e6,'tustin') > bode(h) > > I do not understand why on my plot,i do not read the > same cut off frequency of 8.2 MHZ that i entered in > the code. Instead, at -3dB i get 1.5e7. > Can someone please tell me what i am doing wrong? > > Thanks __________________________________________________