Audio over PWM
Audio over PWM
(OP)
Has anyone tried or does anyone have any experience of transmitting audio using PWM over low cost digital RF transmitter/receiver modules?
I'm looking at some of these license exempt modules and wondering if I can manage to pursuade them to send and receive low bandwidth audio using PWM.
Any ideas or insights would be useful, or if anyone knows of any transceiver modules good for up to about 50m that can send and receive audio that I could use.
UK/Ireland license exempt preferably.
Thanks in advance
I'm looking at some of these license exempt modules and wondering if I can manage to pursuade them to send and receive low bandwidth audio using PWM.
Any ideas or insights would be useful, or if anyone knows of any transceiver modules good for up to about 50m that can send and receive audio that I could use.
UK/Ireland license exempt preferably.
Thanks in advance





RE: Audio over PWM
RE: Audio over PWM
Many CD players use single bit sigma-delta D/A components, but that's not the same as what is actually on the CD.
RE: Audio over PWM
Then, band-limit the pulse stream out of the comparator, and feed inot the mod port.
RE: Audio over PWM
That is, pure PWM from CD player to speaker !
(give or take an LC output filter to reduce the broadcasting from the external wiring)
I think it is called a 'class D' output stage,
and the size of such a thing seems to be extremely small.
(hardly any need for a heatsink)
RE: Audio over PWM
RE: Audio over PWM
As far as the RF is concerned, the output of the sigma-delta or PWM needs to modulated on a carrier. OOK has bad BER, PSK suffers spectral regrowth when using non-linear carrier amps (the cheapest), therefore the best choice is a QPSK derivative or a FSK derivative, MSK etc. These all seem to converge assymtoically on the same solution at the limits of bit-rate/bandwidth, ie. no abrupt phase state changes. With all the digital com chips these days this sould not be to hard to pull off. Then there is a carrier frequency to choose, I prefer the lower freq's, however there is more interference, but filtering is easier
RE: Audio over PWM
Thanks for the comments guys. Pondering and googling will follow...
Spex
RE: Audio over PWM
using rf for phone quality bandwith only requires few components a little microcontroller with an adc module and a citizen band rf transmitter. then check for minimum dt which impose restrictions on Bw.
regards
killa