# Hw-6 - The University of Akron Engineering Faculty...

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The University of Akron Engineering Faculty Electrical & Computer Department Digital Signal Processing I Dr. Roberto J. Acosta Course # 4400:646 Homework # 6 DSP I Student Name : Sriram Yarlagadda Student ID : 2196944 Due Date : 6 March 2009 GRADE :

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Statement of Problem: 1) Consider a multiple carrier system (eg cell phone) that is transmitting to a reference terminal (Cell Tower) using Frequency Division Multiple access 2) The reference terminal is designed to look only at the reference signal and discard or attenuate all other channels PROBLEM-1 Required To detect all frequencies that antenna is picking
1a) How many frequencies are present (Display the Power spectrum)? Solution Using MATLAB for obtaining the solution %Problem -1 Hw-6 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% clc clear all ; close all ; fs=7.28*10^6; % fs-sampling frequency %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Reading an input file %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% load WDBRFSig.m x=WDBRFSig; N=length(x);

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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %performing DFT of the given Analog signal %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% X1=fft(x); X=abs(X1); Xa=X/N; l=1:1:N; figure(1) plot(l*(fs/N),X(l)),grid title( 'DFT of analog wide band signal' ) xlabel( 'Normalized Frequency-Hz' ) ylabel( 'Amplitude' ) TOTAL NO OF FREQUENCIES PRESENT IN THE POWER SPECTRUM=5
PROBLEM 1b,1c Detect the frequencies using DFT(FFT Faster ) and peak finding algorithm? The reference channel will be middle channel (center frequency)? Y=20*log10(X); Ya=20*log10(Xa); figure(2) plot(l*(fs/N),Y(l)),grid title( 'Power Spectrum of Analog input DFT signal' ) xlabel( 'Normalized Frequency--Hz' ) ylabel( 'Power--volts^2' )

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figure(3) plot(l*(fs/N),Y(l)),grid title( 'Zoom in Power Spectrum of Analog input DFT signal' ) xlabel( 'Normalized Frequency--Hz' ) ylabel( 'Power--volts^2' ) axis([420000 490000 50 120])
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %Peak finding Algorithm %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % MaxDFT represents the maximum amplitude in signal MaxDFT=max(Ya); %MaxDFT=14.1203 LIM=MaxDFT-3; j=1; for k=1:1:N/2 if Ya(k)>LIM P(j)=Ya(k); Q(j)=k; j=j+1; end end P; % P represents the amplitude of signal %P=13.8504

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## Hw-6 - The University of Akron Engineering Faculty...

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