Confusion implementing chebyshev type 2 band pass filter in matlab I want to design a band pass Chebyshev Type II filter using analog prototyping. The order of filter is 20 with a value of 60 dB stop band attenuation and 0.75 dB pass band ripple where,
Pass band edge = 800 Hz
Stop band edge = 2000 Hz
Sampling frequency = 6000
My Matlab code is below
clc;  close all;   clear all;
Rp = 0.75;    Rs = 60;
fp = 800;
fs = 2000;
Fs = 6000;

fn = Fs/2;     % nyquist frequency
wp = fp/fn;     % normalized Pass band corner frequency
ws = fs/fn;     % normalized Stop band corner frequency

[n,Wn] = cheb2ord(wp,ws,Rp,Rs);
[num,den] = cheby2(20,Rs,Wn);
freqz(num,den,512,Fs);

I have also attached snapshot of output which shows that output  frequency plot looks like low pass,but i think ,why output plot is not band pass?How can it look band pass?
You're using the function cheb2ord in the wrong way. Assuming that your lower stopband edge is $800$ Hz and your upper stopband edge is $2000$ Hz (note that a bandpass filter has two stopband edges, as well as two passband edges), and if the sampling frequency is $6000$ Hz, then the following command should do what you intended to do:
[b, a] = cheby2(10, 60, [4, 10]/15);
Note that for bandpass and bandstop filters, the resulting filter order is twice the number you use in the call to cheby2.