How to adjust time scale so that when this code is executed ,in frequency domain plot the frequency axis gives value like 210^6 ,310^6 not simple 2,3

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Dipsikha Roy 2020-12-14

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https://ww2.mathworks.cn/matlabcentral/answers/693860-how-to-adjust-time-scale-so-that-when-this-code-is-executed-in-frequency-domain-plot-the-frequency

评论： Dipsikha Roy 2020-12-15

clc

M =8; %here we initialize the number of constellation point of qam

no_of_data_points = 128;

data_source= abs(round(randn(1,10)));%here we take random normal function

figure(1);

stem(data_source);

grid on;

xlabel('Data Points');

ylabel('transmitted data phase representation');

title('Transmitted Data'); %here we plot that transmitted data

qam_modulated_data = qammod(data_source, M); %here we perform 8bit qam on the random normal function

scatterplot(qam_modulated_data);

title('MODULATED TRANSMITTED DATA');%here we plot those constellation point

qam_modulated_data1(1:(M/2))=qam_modulated_data(1:(M/2)); %here we introduce another array named qam_modulated_data1 where first four element is first four constellation point

qam_modulated_data1(((M/2)+1):M)=-qam_modulated_data(1:(M/2));% in my qam_modulated_data1 array last four point is Hermitian of first four point

y=fft(qam_modulated_data1); %here we apply fast Fourier transform on the data of qam_modulated_data1 array

figure(3);

stem(y); %here we plot that fft result

grid on;

xlabel('frequency');

ylabel('amplitude');

title('odd frequency suppressed output');

yc=conj(y);

real_y=y.*yc ;

figure(4);

stem(real_y);

grid on;

xlabel('frequency');

ylabel('amplitude of real values of fft');

title('real value of fft');

1.how to make amplitudes positive?

2.what the changes should be done so that freq axis we get 1*10^6,2*10^6 not just 1,2.

please help.

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Matt Gaidica 2020-12-15

编辑：Matt Gaidica 2020-12-15

在 MATLAB Online 中打开

Can you multiply by -1?
Pass in x-values to the stem() function.

x = [1*10^6, 2*10^6]);
stem(x, real_y*-1);

Dipsikha Roy 2020-12-15

What command should be used to get a graph like this..i want to see the path as well not only points..scatterplot gives me the point only..can u help me please..🙏

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