MATLAB: Cosine Wave understanding Problem

beginnerfhss

Hi, yeah this is probably a lame question : the following code is from fhss by farhat masood on matlab central

link to file : http://www.mathworks.com/matlabcentral/fileexchange/11503-frequency-hopping-spread-spectrum

t=[0:2*pi/119:2*pi]   ;  % Creating 60 samples for one cosine

How is it 60 samples for one cosine ? and what is the freq of the cosine ? also where did 119 come from ?

later used in code as : c=cos(t);

Best Answer

Suppose you used [0:1/2:1] . How many values would be in the vector? Answer: 3, namely 0, 1/2, and 1. And for [0:1/3:1]? Four values, 0, 1/3, 2/3, 1.

Thus [0:2*pi/119:2*pi] will create a vector of 120 total values including the endpoints.

120 is 2 * 60, which suggests that in context the nyquist frequency is being taken in to account.

You might find it easier to understand

linspace(0, 2*pi, 120)

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MATLAB: Half of the progarm showing error

Hi. you need to correct these lines:

c1=[c1 cc1c1c1c1c1c1c1c1 c1]; 
c2=cos(t2); 
c2=[c2 c2c2c2c2 c2];

I edited it:

clc 
clear
% Generation of bit pattern 
s=round(rand(1,25)); 
signal=[]; 
carrier=[]; 
t=[0:2*pi/119:2*pi] 
for k=1:25 
    if s(1,k)==0 
        sig=-ones(1,120); 
    else
        sig=ones(1,120); 
    end
    c=cos(t);
    carrier=[carrier c]; 
    signal=[signal sig]; 
end
subplot(4,1,1);
plot(signal); 
axis([-100 3100 -1.5 1.5]); 
title('\bf\it Original Bit Sequence');
bpsk_sig=signal.*carrier; 
subplot(4,1,2); 
plot(bpsk_sig) 
axis([-100 3100 -1.5 1.5]); 
title('\bf\it BPSK Modulated Signal');
t1=[0:2*pi/9:2*pi]; 
t2=[0:2*pi/19:2*pi]; 
t3=[0:2*pi/29:2*pi]; 
t4=[0:2*pi/39:2*pi]; 
t5=[0:2*pi/59:2*pi]; 
t6=[0:2*pi/119:2*pi]; 
c1=cos(t1); 
c1=[c1 c1 c1 c1 c1 c1 c1 c1 c1 c1 c1 c1]; 
c2=cos(t2); 
c2=[c2 c2 c2 c2 c2 c2]; 
c3=cos(t3); 
c3=[c3 c3 c3 c3]; 
c4=cos(t4); 
c4=[c4 c4 c4]; 
c5=cos(t5); 
c5=[c5 c5]; 
c6=cos(t6);
spread_signal=[]; 
for n=1:25 
    c=randint(1,1,[1 6]); 
    switch(c) 
        case(1) 
            spread_signal=[spread_signal c1]; 
        case(2) 
            spread_signal=[spread_signal c2]; 
        case(3) 
            spread_signal=[spread_signal c3]; 
        case(4) 
            spread_signal=[spread_signal c4]; 
        case(5) 
            spread_signal=[spread_signal c5]; 
        case(6) 
            spread_signal=[spread_signal c6]; 
    end
end
subplot(4,1,3) 
plot([1:3000],spread_signal); 
axis([-100 3100 -1.5 1.5]); 
title('\bf\it Spread Signal with 6 frequencies');
freq_hopped_sig=bpsk_sig.*spread_signal; 
axis([-100 3100 -1.5 1.5]); 
title('\bf\it Frequency Hopped Spread Spectrum Signal');
figure;
subplot(2,1,1) 
plot([1:3000],freq_hopped_sig); 
axis([-100 3100 -1.5 1.5]); 
subplot(2,1,2); 
plot([1:3000],abs(fft(freq_hopped_sig)));

MATLAB: HOW CAN I PLOT THE FOLLOWING POINTS USING SURFACE PLOT

a={[0, 0, 0.3], [1/4, 0, 1.1], [1/2, 0, 2], [3/4, 0, 1.5], [1, 0, 2]...
[0, 1/3, 0.3], [1/4, 1/3, 2], [1/2, 1/3, 1.8], [3/4, 1/3, 1.5], [1, 1/3, 2]...
[0, 2/3, 3], [1/4, 2/3, 2], [1/2, 2/3, 3], [3/4, 2/3, 3.3], [1, 2/3, 3]...
[0, 1, 2], [1/4, 1, 3], [1/2, 1, 2.5], [3/4, 1, 4], [1, 1, 4.5]}
a=cell2mat(a')
x=reshape(a(:,1),5,[])
y=reshape(a(:,2),5,[])
z=reshape(a(:,3),5,[])
mesh(x,y,z)

%or

surf(x,y,z)

Best Answer

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MATLAB: Half of the progarm showing error

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