LNA and Noise Figure improvement

Jean-Samuel Najnudel - BJT PARTNERS SARL jsn at bjtpartners.com
Thu Nov 1 23:48:15 UTC 2012

Hi Andrey,

Would you have some updates about your NF calculations in both 900
(MGA-13116) and 1800 (MGA-13216) bands ?

This information would be very interesting to figure out if we need an
external 1st stage LNA in front of the UmSEL Rx path.
Thanks a lot for your kind help regarding this front-end related question.

Best regards.


On Tue, Oct 30, 2012 at 5:02 PM, Andrey Sviyazov <andreysviyaz at gmail.com>wrote:

> HI Jean-Samuel.
> Not really sure to do UmTRXv3 right now.
> On my opinion now we should found as much issues as possible with v2.
> For example, now I am working with power consumptions.
> I have to think a bit about NF improvement you suggest.
> I'll let you know my calculations by tommorow.
> Best regards,
> Andrey Sviyazov.
> 2012/10/30 Alexander Chemeris <alexander.chemeris at gmail.com>
>> Forwarding to the mailing list.
>> ---------- Forwarded message ----------
>> From: Jean-Samuel Najnudel - BJT PARTNERS SARL <jsn at bjtpartners.com>
>> Date: Tue, Oct 30, 2012 at 6:25 PM
>> Subject: LNA and Noise Figure improvement
>> Hi Andrey,
>> I understand you plan to prepare the UmTRXv3.
>> I would need to discuss about the Rx Noise Figure improvement.
>> With UmSEL, according to your calculations, NF would be around 0.7 dB
>> (excluding duplexer IL) with the MGA-13116.
>> It would be interesting to try to improve this figure with a very
>> first stage LNA based on the MGA-633P8. This would let us reach a NF
>> as low as about 0.4 dB.
>> Adding this very first stage LNA in the Rx path brings a few questions.
>> 1/ To improve isolation with the other RF parts, would we need to have
>> this LNA in a separate shielded enclosure ?
>> If yes, we would need a 5V power supply for this LNA. To have a better
>> shielding between the voltage regulator circuitery and the LNA, it
>> should be nice to have the 5V voltage regulator outside of the LNA
>> enclosure. To make this possible, it would be very useful to add a 5V
>> voltage regulator and connector on the UmTRXv3.
>> If not, we do not need specific modifications on the UmTRXv3 but we
>> would need to add an MGA-633P8/634P8 as a very first stage in the
>> UmSEL.
>> 2/ Whatever external or on the UmSEL, this extra LNA will increase the
>> total gain. Considering your calculation, the UmSEL IIP3 is already as
>> low as around 1 dBm. If we add a very first stage LNA, this IIP3 will
>> go down to about -15 dBm. This could be a problem for inband blockers.
>> Even if, in real life situation in the field, I am not sure it will be
>> a very big problem, it will be a problem to pass the spec.
>> Would you have another idea to improve the NF ?
>> If not, could you please let me know what NF we could expect with the
>> current design (UmSEL with MGA-13116/13216) in both 900 and 1800 bands
>> ?
>> Best regards.
>> Jean-Samuel.
>> :-)
>> --
>> Regards,
>> Alexander Chemeris.
>> CEO, Fairwaves LLC / ООО УмРадио
>> http://fairwaves.ru
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