SDR with HackRF One (Lesson 9: Aliasing)

Lesson 9 Overview

  • Lesson 8 homework review
  • FSK demodulation
  • Negative frequencies
  • Aliasing
  • Lesson 4 homework review
  • Mysteries solved
  • Cosine as sum of two complex exponentials
  • Sampling theorem<
  • Anti-aliasing filters
  • Bandpass sampling

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


1. Create a flowgraph like the one in the screenshot below.

2. Run the flowgraph and use the Average option to view the frequency content of the noise.

3. Add a Low Pass Filter to the flowgraph, using sliders to control the filter’s cutoff frequency and transition width. Configure both sliders with a default value of samp_rate/8, a minimum of samp_rate/1000, a maximum of samp_rate/2, and 1000 steps.

4. Observe how the filter’s frequency response changes when adjusting the sliders. The Average option may be helpful.

5. Check your CPU utilization with the transition width set very low. How does it compare to the utilization observed with the transition width set to a moderate value?

6. Try high pass and band pass filters instead of a low pass filter.


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