1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
|
//Author: Parthasarathi Panda
//parthasarathipanda314@gmail.com
function o=cconv(a,b,n)
// circularly convolves vectors a and b. n is the length of the resulting vector.
//If you omit n, it defaults to length(a)+length(b)-1. When n = length(a)+length(b)-1,
//the circular convolution is equivalent to the linear convolution computed with conv
//Calling Sequence:
//o=cconv(a,b)
//o = cconv(a,b,n)
//a =a real or complex vector.
//b =a real or complex vector.
//n =length of circular convolution
//o =convolution sequence
//Examples:
//a=[1 2 3]
//b=[4 5 6]
//o=cconv(a,b,3)
//Output: o= 31. 31. 28.
//
//
//a=[1 2+%i 4]
//b=[2 3*%i 5]
//o=cconv(a,b)
//o=clean(o)
//
//Output: o= 2. 4. + 5.i 10. + 6.i 10. + 17.i 20.
//
[nargout,nargin]=argn();
if nargin==2 then //to check the number of inputs entered by the user
n=length(a)+length(b)-1;//setting the length of convolution
end
if type(a)~=1 | type(b)~=1 | type(n)~=1 then//to check if the inputs are real/complex arrays
error('check the data type of input');
end
if size(n)~=[1,1] then
error('check the data type of input'); //to check that n is single dimensional
end
if floor(n)~=n | imag(n)~=0 then
error('check that n is an integer');//to check if n is an integer
end
//checking if a is a 1d vector(row or column) and turning it into row vector
[i,j]=size(a);
if j~=1 & i~=1 then
error('a should be a vector');
elseif j==1 //if a column vector make it a row vector
a=a';
end
//checking if b is a 1d vector(row or column) and turning it into row vector
[i,j]=size(b);
if j~=1 & i~=1 then
error('b should be a vector');
elseif j==1//if a column vector make it a row vector
b=b';
end
//adjusting length of a
if n<=length(a) then//if length exceeds n,then take only first n-samples
a=a(1:n);
else//if length is less than n, then pad zeroes
a=[a,zeros(1,n-length(a))]
end
//adjusting length of b
if n<=length(b) then//if length exceeds n,then take only first n-samples
b=b(1:n);
else//if length is less than n, then pad zeroes
b=[b,zeros(1,n-length(b))]
end
//computing ffts (for speed)
aft=fft(a);
bft=fft(b);
//circular convolution dft is the product of dft of the 2
oft=aft.*bft;
o=ifft(oft); //inverse gives circular covolution
endfunction
|
