Pick up WiFi noise

lesept
Posts: 28
Joined: Wed Jun 27, 2018 10:30 pm

Pick up WiFi noise

Postby lesept » Wed Jul 22, 2020 3:14 pm

Hello
In a project I need to create some random white noise at very high frequency (80 MHz). Would it be possible to pick up the noise from the antenna port and amplify it to do this?
If yes, should I connect some wires in parallel to the antenna port of my ESP32 board?

Any idea welcome. Thanks

bobtidey
Posts: 38
Joined: Mon Jun 18, 2018 2:24 pm

Re: Pick up WiFi noise

Postby bobtidey » Wed Jul 22, 2020 9:11 pm

White noise at 80 MHz is a meaningless requirement. White noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. (Wikipedia) So if it was white then the power density would be the same at 1MHz,10MHz,100MHz etc.

If you give some background info on what you are trying to achieve then that would help.

A common simple technique for noise generation is to use a zener diode as a noise source and then amplify it.

e.g. https://www.maximintegrated.com/en/desi ... /3469.html

ESP_Sprite
Posts: 4112
Joined: Thu Nov 26, 2015 4:08 am

Re: Pick up WiFi noise

Postby ESP_Sprite » Thu Jul 23, 2020 7:59 am

Eh, you could define 'white noise at 80MHz' as 'white noise without any components above 80MHz'. Still, agree that e.g. a zener would likely be the way to go, anything that happens on the antenna likely is not very good noise.

lesept
Posts: 28
Joined: Wed Jun 27, 2018 10:30 pm

Re: Pick up WiFi noise

Postby lesept » Thu Jul 23, 2020 8:18 am

Thanks for your answers. You are right, I need to give more details.

I want to generate a different random voltage value 80 million times per second. I am currently considering the Zener circuit, but as I saw that the ESP32's true random number generator was based on reading the antenna voltage (or something similar), I thought I could use this kind of trick to generate these voltages.

I guess that, if it's called 'true' random generator, the antenna voltage is used every time and not only for seeding a pseudo random generator.

If my antenna is in a Wifi range, it should generate a voltage that varies at a frequency close to 4GHz. So 80MHz should be achievable.

This would eliminate the need for the Zener diode, and I would just need to amplify the voltage.
Is this possible?

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