SDR Modulation & Demodulation Experiments

Problem

The goal of this project was to move beyond purely simulated modulation schemes and observe how digitally generated signals behave in real RF environments. I aimed to design modulation chains in GNU Radio and transmit/receive them using actual SDR hardware.

Approach

I implemented modulation and demodulation blocks for FM, AM, PSK, and QAM using GNU Radio flowgraphs. These signals were transmitted and received using an RTL-SDR device, enabling real-time observation and analysis.

Tools

• GNU Radio
• RTL-SDR
• Real-time spectrum and constellation analysis

Results

I successfully generated and processed real-time RF signals, observed the practical effects of different modulation schemes, and evaluated their suitability for my own application-level designs.

What I Learned

This project strengthened my understanding of SDR workflows, GNU Radio design, and the gap between ideal simulations and real-world RF behavior. It also improved my intuition for selecting modulation techniques based on practical constraints.