UmTRX preselector

Andrey Sviyazov andreysviyaz at gmail.com
Mon Aug 13 09:08:29 UTC 2012


Hi all.

I have question about preselector improving:
Do we need on-board eeprom for identification?
It also can contain band and IF freq values, T'C look-up table for SAW, etc.

Best regards,
Andrey Sviyazov.



2012/8/9 Andrey Sviyazov <andreysviyaz at gmail.com>

>
> 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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