Question

3) Develop Matlab code to plots of chirp signal and its FFT (sampling frequency-500 Hz, duration: 1 second, length of FFT 1024). Explain what chirp signal is and how it is using in industry

Answer 1

Fs=500; % sample rate

tf=1; % 1 seconds

t=0:1/Fs:tf-1/Fs;

f1=100;

f2=400; % start @ 100 Hz, go up to 400Hz

semi_t=0:1/Fs:(tf/2-1/Fs);

sl=2*(f2-f1/2);

f1=f1*semi_t+(sl.*semi_t/2);

f2=f1(end)+f2*semi_t-sl.*semi_t/2;

f=[f1 f2];

y=1.33*cos(2*pi*f.*t);

soundsc(y,Fs)

spectrogram(y,1024,[],1024,Fs,'yaxis')

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A chirp is a signal in which the frequency increases (up-chirp) or decreases (down-chirp) with time. In some sources, the term chirp is used interchangeably with sweep signal.In spread-spectrum usage, surface acoustic wave (SAW) devices such as reflective array compressors (RACs) are often used to generate and demodulate the chirped signals. In optics, ultrashort laser pulses also exhibit chirp, which, in optical transmission systems, interacts with the dispersion properties of the materials, increasing or decreasing total pulse dispersion as the signal propagates.

APPLICATIONS

It is commonly used in sonar, radar, and laser, but has other applications, such as in spread-spectrum communications.