Assignment Digital Communication
Added on - 03 May 2020
Signal Processing for Digital Radio ReceiversSignal2:It is an artificial signal consisting of several signal components. FromMATLAB, it is possible to perform spectrum estimation to identify the component of thesignal usingperiodogram and spectrogram techniques. The following code is used:MATLAB code:clc;% clear command windowclear;% clear work spacecloseall;%close all figures% read signal Signal2.wavSignal2=audioread('Signal2.wav');sound(Signal2)%play the sound% plot the Periodogram of the signal: it helps to visualize the frequency% of the signal on x-axis and magnitude of spectrum as y-axis.clcperiodogram(Signal2)00.10.20.30.22.214.171.124.80.91Normalized Frequency (rad/sample)-70-60-50-40-30-20-10010Power/frequency(dB/rad/sample)Periodogram Power Spectral Density EstimateFigure 1.1: Periodogram estimate.From the figure 1.1, the normalized frequency of the signal is observed. It can beseen that the signal contains two (2) different signal in signal2.wav signal. Onefrequency spectrum is plotted with blue color and the other one brown color.
The Signal2 is filtered with the rectangular window of length1024 which is thesame length of Signal2. The PSD (Power Spectral Density) estimate here is calculatedby use of an FFT of length greater than 256, i.e2n∧n=8greater than 1024 i.e.n≥10Furthermore, the rectangular window used had a sidelobe attenuation of 13.3 dB.Using signalAnalyzer to analyze Signal2signalAnalyzer(Signal2):It is still shown that Signal2 has two (2) signal with different frequencies as shown infigure 1.2 below. It shows that both signals have 1024 samplesFigure 1.2: Signal analysis using signalAnalyzerFrom figures 1.1 and 1.2, the power spectral density (PSD) of the two (2)displayed signals describes the power present in the each signal as a function of perunit frequency..Signal5:Is a simulated backscatter received by a simple radar. The received signal isstored in the variable rx, and the transmitted signal is stored in the variable tx.
clc;% clear command windowclear;% clear work spacecloseall;%close all figures% read the transreceiver signal Signal5.wavSignal5=load('Signal5.mat')%find the information about the signal5matFile = matfile('Signal5.mat','Writable',true);whos(matFile)Signal5 =struct with fields:fs: 1.0000e+09xr: [1×10000 double]xt: [1000×1 double]Name Size Bytes Class Attributesfs 1x1 8 doublexr 1x10000 160000 double complexxt 1000x1 16000 double complexFrom the above MATLAB simulation, the characteristics of the transmit waveformis seen has 1000 samples. The receiver have10000 samples. The operating frequencyof the radar is1.0×109Hz..Figure 2.1 is a spectrogram of the transmitter (xt) and figure 2.2 is thespectrogram of the receiver (xr). The following code is used to plot the spectrograms ofxt and xrfigure()spectrogram(Signal5.xt)figure()spectrogram(Signal5.xr).