[USRP-users] The receiver ADC goes into saturation

Marcus Müller marcus.mueller at ettus.com
Sat Oct 25 09:23:38 EDT 2014


Hi XD,

On 25.10.2014 14:28, w xd via USRP-users wrote:
> Hi all:
>        Environment:USRP N210,14bit ADC
>        According the formula:DR(dynamic range):6.02*14=84.28dB.
That is the theoretical formula for the maximum dynamic range you get
from an ADC.
Most daughterboards have, like yours, adjustable gain. You'd need to add
that gain range to the ADC dynamic range to get the upper boundary of
dynamic range that your receiver system can deal with.

>        And now two USRP N210 close to each other,while one is used for
> transmitting and the other is used for receiving.The amplitude of the
> signal which to be send is 1.The gain in the transmitter I set
> 31.5dB.And the gain in the receiver I set also 31.5dB.The
> 31.5dB*2=63<DR(dynamic range).Why the receiver goes in saturation so
> easily?The signal saturates the ADC and gets clipped.Can someone
> explain it to me?
Yes. Dynamic range but defines the ratio between the strongest
detectable and the weakest detectable signal amplitude. Obviously,
you're overdriving you ADC -- why don't you just reduce the RX gain? The
multiplied gains of RX and TX tell you nothing about the strength of the
signal reacing your RX USRP.

Greetings,
Marcus

>        Thank you.
> Best regards,
> xd
>
>
>
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