GSM-noise "buzz" issue / ways forward
andy at openmoko.com
Mon Sep 22 16:10:35 CEST 2008
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Somebody in the thread at some point said:
|> Completely agree, but MICBIAS gets something different from HF during
|> the buzz behaviour, it gets small depressions (like 100mV IIRC) in it at
|> ~200Hz period. Basically it is exactly like the PSRR was very low and
Power Supply Rejection Ratio, ie, bleed through of noise on power rail
to the output. This 200Hz noise is visible at the battery, it makes
sense because there is big current draw when GSM thing transmits in one
of its slots, it depresses the voltage at the battery.
|> What I don't understand is how we get from 1.7GHz "infestation", which
|> is clearly an issue since a bead on p4 of the headset jack does
|> something, to these LF "dents" on MICBIAS.
| Do we have a sound recording of this buzz?
Joerg got a sufferer to call him on his answering machine, I will send
you a copy of it offlist (since it is too big for the list).
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