## Wednesday, April 3, 2013

### ADC and DAC using MATLAB

Here we add some Gaussian noise to the input sine wave and then will will convert that to digital signal. This digital signal sampled data will be used in Modelsim. In the modelsim we develop moving average filter using VHDL, this will filters the sampled data and writes into another file. Using the new updated sampled data we will regenerate the Analog signal.

clear all;
close all;
clc;
fs=500000;
% taking sampling frequency as 500kHz
fm=10000;
% input signal frequency 10kHz
t=1:200;     % displaying 200 samples
x=5*cos(2*pi*(fm/fs)*t);
%input sinusoidal signal
z=awgn(x,1);
% adding white Gaussian noise to the input signal with S/N=1
h=1:1000;
plot(t,x,'g','LineWidth',2);
% plotting input signal
hold on;
plot(t,z,'r','linewidth',1.5);
% plotting noisy signal
hold on;
stem(t,z);
hold on;
Vd=-5:0.0390625:5; % step size =0.0390625, when n=8 bits
for i=1:256
Vdelta(i)=(Vd(i)+Vd(i+1))/2;
% Quantization levels
end

i=0:255;
binary= dec2bin(i);
% decimal to binary conversion
% Quantization of input signal

for i=1:200
for j=1:256
if(z(i)< Vd(1))
z(i) = Vdelta(1);
end
if (z(i) > Vd(257))
z(i) = Vdelta(256);
end
if(z(i) <= Vd(j+1) && z(i) >= Vd(j))
z(i) = Vdelta(j);
end
end
end

% Encoding the Quantized data
for i=1:200
for j=1:256
if (z(i)==Vdelta(j))
B_data(i,1:8) = binary(j,1:8);
end
end
end
% representing binary data in decimal
figure
for i=1:200
B(i)=bin2dec(B_data(i,1:8));
end

% First solution; writing Encoded data into ADC.txt file. The we will perfom
% Moving average filter operation in VHDL
for n = 1:200
fprintf(f, '%s\n', B_data(n,1:8));
end
fclose(f);
subplot(221);
plot(x);
title('original sinwave','fontsize',12);
xlabel('--->time in 2us');
ylabel('--->amplitude in volts');
subplot(222);
plot(z);
title('noise signal','fontsize',12);
xlabel('--->time in 2us');
ylabel('--->amplitude in volts');
% After the moving avg filter the filtered data has been written to vhdl_out.txt file
f=fopen('vhdl_out.txt','r');
A = fscanf(f,'%g',[1 inf]);
fclose(f);

subplot(224)
plot(B)
title('signal with white gaussian noise','fontsize',12);
xlabel('--->time in 2us');
ylabel('--->amplitude in decimal');
%Digital to Analog conversion
for i=1:192
for j=1:256
if(A(i)== j )
outpt(i)=Vdelta(j);
end
end
end

subplot(223);
plot(outpt);
title('filtered sine wave sinewave output','fontsize',12);
xlabel('--->time in 2us');
ylabel('--->amplitude in decimal');

RESULT:
Output data files