Graphics Programs Reference
In-Depth Information
y6= y6(1+(m6-1)/2:end-(m6-1)/2,1);
y6(end+1:end+m6-1,1)=zeros(m6-1,1);
We obtain an output vector
y6
of the same length and phase as the input
vector
x6
. We plot the results for comparison.
stem(t,x6)
hold on
stem(t,y6,'filledv,'r')
axis([0 20 -2 2])
In contrast to
plot
, the function
stem
only accepts one data series.
Therefore, the second series
y6
is overlaid on the same plot using the func-
tion
hold
. The effect of the fi lter is clearly seen on the plot. It averages the
unit impulse over a length of fi ve elements. Furthermore, the values of the
output equal the fi lter weights of
a6
, in our example 0.2 for all elements of
a6
and
y6
.
For a recursive fi lter, the output
y6
does not agree with the fi lter weights.
Again, impulse is generated fi rst.
clear
t = (0:20)';
x7 = [zeros(10,1);1;zeros(10,1)];
Subsequently, an arbitrary recursive fi lter with weights of
a7
and
b7
is de-
signed.
b7 = [0.0048 0.0193 0.0289 0.0193 0.0048];
a7 = [1.0000 -2.3695 2.3140 -1.0547 0.1874];
m7 = length(b7);
y7 = filter(b7,a7,x7);
y7= y7(1+(m7-1)/2:end-(m7-1)/2,1);
y7(end+1:end+m7-1,1)=zeros(m7-1,1);
The stem plot of the input
x2
and the output
y2
shows an interesting impulse
response:
stem(t,x7)
hold on
stem(t,y7,'filled','r')
axis([0 20 -2 2])
The signal is again smeared over a wider area. It is also shifted towards the
right. Therefore this fi lter not only affects the amplitude of the signal, but
also shifts the signal towards lower or higher values. In most cases, phase
shifts are unwanted characteristics of fi lters, although in some applications
shifts along the time axis might of particular interest.
