Saturday, October 20, 2012

Generating Echo

Step-1 Taking a recorded data of wcdma signal with following specs

sample rate - 12.5MSPS
center frequency - 2.15149GHz
power level - (-65dB)
number of complex samples - 1e7

File is located in /home/sumit/wcdma_data_dump

Step-2 Reading the data in matlab with the following process

cd /home/sumit/wcdma_data_dump/ % go to current directory

fid = fopen('/home/sumit/wcdma_data_dump/wcdma_65','rb'); % open file descriptor

wcdma_matlab_65 = fread(fid,20000000,'float32'); % read the binary file as 32 bit complex float
% i.e. 32 bits for I and 32 bits for Q

fclose(fid); % close the file descriptor essentially
save('wcdma_matlab_65.mat','wcdma_matlab_65'); % save the current data in .mat format
% now we will ignore first 400000 samples because there was a peak there
% because of the LO leakage

wcdma_noleak_65 = wcdma_matlab_65(800000:20000000);
% I have taken 800000 because the samples are here in the format of I and Q
% cascaded

% creating the data with no LO leakage

temp1 = wcdma_noleak_65; 

cd /home/sumit/wcdma_data_dump/

fid = fopen('temp1.bin','wb');

fwrite(fid,temp1,'float32'); % created binary file for the no LO leakage data


Step-3 Echo generation

Xecho(t-delay) = X(t-0) + X(t-delay)

I made following flow graph
Step-4 Echo Visualization 

Echo affected signal looks like this

While the original signal looked like this

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