SDR with HackRF One (Lesson 7: Complex Numbers in DSP)

Lesson 7 Overview

  • Lesson 6 homework review
  • Why we use complex numbers in DSP
  • Amplitude modulation
  • Frequency modulation

In order to clearly see my screen during the demonstration, viewing the video in full screen mode may help. Even better: You can download this video in high resolution (720p). (torrent)


  1. Launch GNU Radio Companion and locate the block called Quadrature Demod. This block implements the method for frequency demodulation presented in the video. Notice that it takes complex input and produces real-valued (float) output which is a sequence of angles.
  2. Can you find a block that implements our method of amplitude demodulation? It should take complex input and produce real-valued (float) output where each output sample is the magnitude of an input sample.


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