[USRP-users] Improving Sensitivity of the Radio.

Kyeong Su Shin ksshin at uw.edu
Tue Nov 14 22:31:15 EST 2017


Dear Marcus D. Leech:

Thank you for the reply.

Is the only advantage of the TwinRX the pre-selector filter bank? Or, can
the superheterodyne design of the radio also affect the data quality in
some ways?

We do turn down the gain to get optimal results. (The 'noise figure' that I
mentioned was the noise figure that is observed by us, after such
adjustments). We will definitely try adding filters.

Regards,
Kyeong Su Shin

On Tue, Nov 14, 2017 at 7:12 PM, Marcus D. Leech via USRP-users <
usrp-users at lists.ettus.com> wrote:

> On 11/14/2017 10:00 PM, Kyeong Su Shin via USRP-users wrote:
>
> Hello Everyone:
>
> We are using USRPs for spectrum sensing (on pretty much any frequencies).
> Before asking my faculty to order a TwinRX daughterboard, however, I would
> like to see if there are any ways to improve the sensitivity of the
> hardware that we currently own (UBX/SBX/CBX/WBX).
>
> Our USRP + UBX configuration works well, except that we cannot really
> increase the gain level much without putting the RF frontend into the
> nonlinear region. Because of this, the noise figure of our data is about
> ~30dB in the worst case. I believe that the main problem is that we are
> using a wideband outdoor discone antenna for this - dumping quite a lot of
> RF energy to the RF frontend.
>
> In this case, what could I try to improve the sensitivity of the radio? I
> think one option could be adding additional filters to the chain (when we
> know that we are only looking at a certain frequencies), but I wonder if
> there are anything else that I can try.
>
> Also, I wonder what differences we can expect if we switch our
> daughterboard to a TwinRX. Would it be worth it? What noise figures did
> people experience when a wideband outdoor antenna was connected to the
> board?
>
> Regards,
> Kyeong Su Shin
>
>
> _______________________________________________
> USRP-users mailing listUSRP-users at lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
> In the case of overload, the noise-figure is NOT the dominating factor in
> determining system sensitivity.
>
> If you are "sensing" across a limited band, then a filter that covers that
> band, and that band only, will definitely help keep the very first gain
> stages,
>   which are "wide open" from going into overload.
>
> The TwinRX has some significant advantage here, since it has pre-selector
> filters, but those filters may or may not have band edges that correspond
>   adequately to the band that your are "sensing".
>
> Basically, there's a "tension" in small-signal RF amplifiers.   They can
> either have very high dynamic range, or they can have very-low noise figure.
>   That general axiom still applies, although things are getting somewhat
> better in this regard.    But taking the output of an outdoor disc-cone
> antenna
>   in a normal urban environment is pretty-much begging for
> non-linearity.    You might try turning *down* the gain.
>
>
>
>
>
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>
>
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