How to plot the frequency of OFDM signals....??

[Jobagent]

ofdm signals

I have a sequence of 16-QAM symbols with N number of subcarriers.....

I want to have a look on the frequency domain of the code....anyone got an idea how to do it?

 

[yjscumtb]

dvb-t baseband signal bandwidth

use ur QAM16 datas to modulate N cos2*pi*f(i)*t+jsin2*pi*f(i)*t and make sure the N sinusoid wave orthogonal. do fft and plot the magnitude then u will see u want to see

 

[forget]

how to plot ofdm

use matlab? or other tools, are there any more tools about display waveform,thanks

 

[gayathri123]

how to plot a rand signal in matlab?

to send subcarriers from baseband signal can i help phase shift keying as input signal.

 

[Communications_Engineer]

signal matlab phase shift p(t- ofdm

yeah you can use psk as well no prob

 

[Aya2002]

plot of ofdm symbol

hi friends

do u have the code in matlab?

appreciated

 

[mashhur]

ofdm pulse shape

type in mathworks.com "16-QAM", you can find the Matlab code which you want

good luck!

 

[Aya2002]

signal carrier plot

hi dear i come back again: please see this code for complete OFDM simulation with all the figures

%DVB-T 2K Transmission
%The available bandwidth is 8 MHz
%2K is intended for mobile services
clear all;
close all;
%DVB-T Parameters
Tu=224e-6; %useful OFDM symbol period
T=Tu/2048; %baseband elementary period
G=0; %choice of 1/4, 1/8, 1/16, and 1/32
delta=G*Tu; %guard band duration
Ts=delta+Tu; %total OFDM symbol period
Kmax=1705; %number of subcarriers
Kmin=0;
FS=4096; %IFFT/FFT length
q=10; %carrier period to elementary period ratio
fc=q*1/T; %carrier frequency
Rs=4*fc; %simulation period
t=0:1/Rs:Tu;
%Data generator (A)
M=Kmax+1;
rand('state',0);
a=-1+2*round(rand(M,1)).'+i*(-1+2*round(rand(M,1))).';
A=length(a);
info=zeros(FS,1);
info(1A/2)) = [ a(1A/2)).']; %Zero padding
info((FS-((A/2)-1)):FS) = [ a(((A/2)+1):A).'];
%Subcarriers generation (B)
carriers=FS.*ifft(info,FS);
tt=0:T/2:Tu;
figure(1);
subplot(211);
stem(tt(1:20),real(carriers(1:20)));
subplot(212);
stem(tt(1:20),imag(carriers(1:20)));
figure(2);
f=(2/T)*(1FS))/(FS);
subplot(211);
plot(f,abs(fft(carriers,FS))/FS);
subplot(212);
pwelch(carriers,[],[],[],2/T);
% D/A simulation
L = length(carriers);
chips = [ carriers.';zeros((2*q)-1,L)];
p=1/Rs:1/Rs:T/2;
g=ones(length(p),1); %pulse shape
figure(3);
stem(p,g);
dummy=conv(g,chips));
u=[dummy(1:length(t))]; % (C)
figure(4);
subplot(211);
plot(t(1:400),real(u(1:400)));
subplot(212);
plot(t(1:400),imag(u(1:400)));
figure(5);
ff=(Rs)*(1q*FS))/(q*FS);
subplot(211);
plot(ff,abs(fft(u,q*FS))/FS);
subplot(212);
pwelch(u,[],[],[],Rs);
[b,a] = butter(13,1/20); %reconstruction filter
[H,F] = FREQZ(b,a,FS,Rs);
figure(6);
plot(F,20*log10(abs(H)));
uoft = filter(b,a,u); %baseband signal (D)
figure(7);
subplot(211);
plot(t(80:480),real(uoft(80:480)));
subplot(212);
plot(t(80:480),imag(uoft(80:480)));
figure(8);
subplot(211);
plot(ff,abs(fft(uoft,q*FS))/FS);
subplot(212);
pwelch(uoft,[],[],[],Rs);
%Upconverter
s_tilde=(uoft.').*exp(1i*2*pi*fc*t);
s=real(s_tilde); %passband signal (E)
figure(9);
plot(t(80:480),s(80:480));
figure(10);
subplot(211);
%plot(ff,abs(fft(((real(uoft).').*cos(2*pi*fc*t)),q*FS))/FS);
%plot(ff,abs(fft(((imag(uoft).').*sin(2*pi*fc*t)),q*FS))/FS);
plot(ff,abs(fft(s,q*FS))/FS);
subplot(212);
%pwelch(((real(uoft).').*cos(2*pi*fc*t)),[],[],[],Rs);
%pwelch(((imag(uoft).').*sin(2*pi*fc*t)),[],[],[],Rs);
pwelch(s,[],[],[],Rs);
%DVB-T 2K Reception
clear all;
close all;
Tu=224e-6; %useful OFDM symbol period
T=Tu/2048; %baseband elementary period
G=0; %choice of 1/4, 1/8, 1/16, and 1/32
delta=G*Tu; %guard band duration
Ts=delta+Tu; %total OFDM symbol period
Kmax=1705; %number of subcarriers
Kmin=0;
FS=4096; %IFFT/FFT length
q=10; %carrier period to elementary period ratio
fc=q*1/T; %carrier frequency
Rs=4*fc; %simulation period
t=0:1/Rs:Tu;
tt=0:T/2:Tu;
%Data generator
sM=2;
[x,y] = meshgrid((-sM+1):2sM-1),(-sM+1):2sM-1));
alphabet = x) + 1i*y);
N=Kmax+1;
rand('state',0);
a=-1+2*round(rand(N,1)).'+i*(-1+2*round(rand(N,1))).';
A=length(a);
info=zeros(FS,1);
info(1A/2)) = [ a(1A/2)).'];
info((FS-((A/2)-1)):FS) = [ a(((A/2)+1):A).'];
carriers=FS.*ifft(info,FS);
%Upconverter
L = length(carriers);
chips = [ carriers.';zeros((2*q)-1,L)];
p=1/Rs:1/Rs:T/2;
g=ones(length(p),1);
dummy=conv(g,chips));
u=[dummy; zeros(46,1)];
[b,aa] = butter(13,1/20);
uoft = filter(b,aa,u);
delay=64; %Reconstruction filter delay
s_tilde=(uoft(delay+(1:length(t))).').*exp(1i*2*pi*fc*t);
s=real(s_tilde);
%OFDM RECEPTION
%Downconversion
r_tilde=exp(-1i*2*pi*fc*t).*s; %(F)
figure(1);
subplot(211);
plot(t,real(r_tilde));
axis([0e-7 12e-7 -60 60]);
grid on;
figure(1);
subplot(212);
plot(t,imag(r_tilde));
axis([0e-7 12e-7 -100 150]);
grid on;
figure(2);
ff=(Rs)*(1q*FS))/(q*FS);
subplot(211);
plot(ff,abs(fft(r_tilde,q*FS))/FS);
grid on;
figure(2);
subplot(212);
pwelch(r_tilde,[],[],[],Rs);
%Carrier suppression
[B,AA] = butter(3,1/2);
r_info=2*filter(B,AA,r_tilde); %Baseband signal continuous-time (G)
figure(3);
subplot(211);
plot(t,real(r_info));
axis([0 12e-7 -60 60]);
grid on;
figure(3);
subplot(212);
plot(t,imag(r_info));
axis([0 12e-7 -100 150]);
grid on;
figure(4);
f=(2/T)*(1FS))/(FS);
subplot(211);
plot(ff,abs(fft(r_info,q*FS))/FS);
grid on;
subplot(212);
pwelch(r_info,[],[],[],Rs);
%Sampling
r_data=real(r_info(12*q):length(t)))... %Baseband signal, discrete-time
+1i*imag(r_info(12*q):length(t))); % (H)
figure(5);
subplot(211);
stem(tt(1:20),(real(r_data(1:20))));
axis([0 12e-7 -60 60]);
grid on;
figure(5);
subplot(212);
stem(tt(1:20),(imag(r_data(1:20))));
axis([0 12e-7 -100 150]);
grid on;
figure(6);
f=(2/T)*(1FS))/(FS);
subplot(211);
plot(f,abs(fft(r_data,FS))/FS);
grid on;
subplot(212);
pwelch(r_data,[],[],[],2/T);
%FFT
info_2N=(1/FS).*fft(r_data,FS); % (I)
info_h=[info_2N(1:A/2) info_2N((FS-((A/2)-1)):FS)];
%Slicing
for k=1:N,
a_hat(k)=alphabet((info_h(k)-alphabet)==min(info_h(k)-alphabet)); %(J)
end;
figure(7)
plot(info_h((1:A)),'.k');
title('info-h Received Constellation')
axis square;
axis equal;
figure(8)
plot(a_hat((1:A)),'or');
title('a_hat 4-QAM')
axis square;
axis equal;
grid on;
axis([-1.5 1.5 -1.5 1.5]);

also i attached it here you can download it i test it it is work

 

[Communications_Engineer]

fs= a baseband signal

Do you know why there are smilies in your code?

 

[Aya2002]

dvb-t baseband elementary period

yes

it is because of the paranthesis and colone and simicolons