Author Topic: HackRF sample_rate question  (Read 859 times)

0 Members and 1 Guest are viewing this topic.

Offline salviador

  • Regular Contributor
  • *
  • Posts: 61
  • Country: it
    • https://www.youtube.com/user/mancio92M
HackRF sample_rate question
« on: June 30, 2017, 10:08:34 am »
I'm confused about the sample rate issue, Nyquist-Shannon says:
"The minimum sampling frequency of That signal must be at least twice its maximum frequency"

But in the example of hackrf the sample rate is Is lower than the frequency you want to receive, example the FM receiver

Why?
 

Offline danadak

  • Super Contributor
  • ***
  • Posts: 1875
  • Country: us
  • Reactor Operator SSN-583, Retired EE
Re: HackRF sample_rate question
« Reply #1 on: June 30, 2017, 10:22:54 am »
Love Cypress PSOC, ATTiny, Bit Slice, OpAmps, Oscilloscopes, and Analog Gurus like Pease, Miller, Widlar, Dobkin, obsessed with being an engineer
 

Offline ataradov

  • Super Contributor
  • ***
  • Posts: 5967
  • Country: us
    • Personal site
Re: HackRF sample_rate question
« Reply #2 on: June 30, 2017, 03:48:36 pm »
Not the maximum frequency, but the maximum bandwidth. You can sample 1 MHz band at 100 MHz central frequency with 2 MHz ADC and recover the signal (provided your filters are ideal of close). This is called undersampling, and this technique is often used in practice.

This note is unrelated to Hack_RF, I don't know what they are doing there.

In the bottom left box, you can see that they are interested in the 200 kHz bandwidth, so sampling it at 20 MHz is not a problem.
« Last Edit: June 30, 2017, 03:50:50 pm by ataradov »
Alex
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf