EC22 · Sem 5 · Digital signal processing

Spectrum of a chirp (frequency sweep)

Aim: See how a linear chirp spreads across the spectrum and on the waterfall.

🧪 Live simulation🧊 Real-time 3D bench⚠ Simulated values, not physical measurements

🔬 Virtual lab

Starting the lab…

📘 Theory

A chirp sweeps its frequency over time. Its FFT is broad, but the waterfall (short-time Fourier transform) shows the frequency rising row by row: the basis of radar pulse compression and LoRa.

f(t) = f₀ + k·t

🧰 Apparatus (virtual)

Chirp generator
spectrum analyser with waterfall

📝 Procedure

Select the chirp signal
Watch the waterfall surface
Compare the single FFT with the waterfall
Explain time–frequency resolution

Observations and result (kept on this device)

🎤 Viva questions

Why does LoRa use chirps

They are robust to noise and Doppler and allow long range at low power.

What does the waterfall add over one FFT

How the spectrum changes with time.

🛡️ Safety

Virtual lab. With real RF equipment, respect exposure limits, never transmit without a licence, and keep antennas away from people.