UmTRX preselector

Andrey Sviyazov andreysviyaz at gmail.com
Thu Aug 9 05:17:38 UTC 2012


08.08.2012 22:46 пользователь "Sylvain Munaut" <246tnt at gmail.com> написал:
>
> Hi,
>
> > Its about far-near problem (05.05 p.5.1), i.e. blocking by near mobile
with
> > high signal at only 600kHz offset.
> > Therefore, calculated that LO noise at 600kHz offset should be around
> > -140dBc/Hz to keep nominal Rx sencitivity for wanted far mobile.
>
> Mmm, interesting, I had never thought about this.
>
> Can you confirm my computation is the right one :
>
> Minimum Ec/No of 8 dB, thernal noise of GSM ~ -120 dBm, so the weakest
> mobile would be a -112 dBm.
>
> The interference I see specified in 05.05 is a -26 dBm sine, so with
> -140 dBc/Hz you'd get a -166 dBm 'leak' of the interference in the
> signal of interest at any given position, which you need to integrate
> over the entire useful bandwidth of the GSM signal ( 271 kHz -> 10 *
> log10(271e3) = 54 dB ), which would give a -112 dBm noise.
>
> Cheers,
>
>     Sylvain
Yes, your computation confirm that we can get  noise flour -109 dBm in
summary.
But I can't understand this stupid requirement.
Really blocker it is mobile signal, therefore it will make direct jumming
due to GMSK spectrum mask.
What do you think about it?

Best regards,
Andrey Sviyazov.
(Sent from my mobile client)
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