Daniel.liwag: Created page with "% Lowpass filter a discrete-time signal consisting of two sine waves. % Use MATLAB to design a lowpass FIR filter with the Parks-Mclellan % (Remez) method.Specify the passband f…"

2013-12-18T21:06:05Z

Created page with "% Lowpass filter a discrete-time signal consisting of two sine waves. % Use MATLAB to design a lowpass FIR filter with the Parks-Mclellan % (Remez) method.Specify the passband f…"

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% Lowpass filter a discrete-time signal consisting of two sine waves.

% Use MATLAB to design a lowpass FIR filter with the Parks-Mclellan
% (Remez) method.Specify the passband frequency to be 0.15? radians/sample
% and the stopband frequency to be 0.25? radians/sample. Specify 1 dB of
% allowable passband ripple and a stopband attenuation of 60 dB.

clc
clear all
close all

% Query the valid design methods for your filter specification object, d.
d=fdesign.lowpass('Fp,Fst,Ap,Ast',0.15,0.25,1,60);

% Ap — amount of ripple allowed in the pass band in decibels (the default
% units).
% Ast — attenuation in the stop band in decibels (the default units).
% Fp — frequency at the start of the pass band. Specified in normalized
% frequency units.
% Fst — frequency at the end of the stop band. Specified in normalized
% frequency units.

% Create an FIR equiripple filter and view the filter magnitude response
% with fvtool.
designmethods(d);

% Create a signal consisting of the sum of two discrete-time sinusoids
% with frequencies of ?/8 and ?/4 radians/sample and amplitudes of
% 1 and 0.25 respectively. Filter the discrete-time signal with the FIR
% equiripple filter object, Hd.
Hd = design(d,'equiripple');
fvtool(Hd);

n = 0:159;
x = 0.25*cos((pi/8)*n)+sin((pi/4)*n);
y = filter(Hd,x);
Domega = (2*pi)/160;
freq = 0:(2*pi)/160:pi;
xdft = fft(x);
ydft = fft(y);
plot(freq,abs(xdft(1:length(x)/2+1)));
hold on;
plot(freq,abs(ydft(1:length(y)/2+1)),'r','linewidth',2);
legend('Original Signal','Highpass Signal','Location','NorthEast');
ylabel('Magnitude'); xlabel('Radians/Sample');

% Create a filter of order 10 with a 6-dB frequency of 9.6 kHz and a
% sampling frequency of 48 kHz.
d=fdesign.lowpass('N,Fc',10,9600,48000);
designmethods(d);

% % Display filter magnitude response
Hd = design(d);
% Zoom in on the magnitude response to verify that the -6 dB point is at
% 9.6 kHz.
fvtool(Hd);

% References:
% http://eeweb.poly.edu/iselesni/EL713/remez/remez.pdf
% http://www.mathworks.com/help/signal/ref/fdesign.lowpass.html

Alex Haesche - Revision history

Daniel.liwag: Created page with "% Lowpass filter a discrete-time signal consisting of two sine waves. % Use MATLAB to design a lowpass FIR filter with the Parks-Mclellan % (Remez) method.Specify the passband f…"