# Resolution of USRP N210 and N200

**URL:** <https://www.ruby-forum.com/t/resolution-of-usrp-n210-and-n200/237273>\
**Category:** GNU Radio\
**Created:** [November 2, 2013, 8:23am UTC](https://www.ruby-forum.com/t/resolution-of-usrp-n210-and-n200/237273 "2013-11-02T08:23:39Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\
**Post date:** [November 2, 2013, 8:23am UTC](https://www.ruby-forum.com/t/resolution-of-usrp-n210-and-n200/237273/1 "2013-11-02T08:23:39Z")

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Hi,

Both of USRP N210 and N200 have 14 bit ADC, which means a range of  
+/-2e13=+/-8129.

However, as I tested a N210 with LFRX, I got values from -32704 ~ 30073,  
close to +/-2e15=32768.

Last year, I also tested a N200 with LFRX, I got values from -16357 ~  
16241,  
close to +/-2e14=16384.

The sampling rate was set to 4 MHz.

So why does the ADC has a real resolution higher than 14 bit, and are  
N210  
and N200 the same?

I’m really new to the world of ADC, so some basics would be very  
helpful.

Thanks!

Wu

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**Author:** ![Ting\_Wu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/3bc359/32.png) [@Ting\_Wu](https://www.ruby-forum.com/u/Ting_Wu)\
**Post date:** [November 5, 2013, 8:35pm UTC](https://www.ruby-forum.com/t/resolution-of-usrp-n210-and-n200/237273/2 "2013-11-05T20:35:58Z")

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Ting -

This question really isn’t GNURadio related. If you resend it over the  
USRP-Users list, though, we will help explain things quickly!

[http://lists.ettus.com/mailman/listinfo/usrp-users\_lists.ettus.com](http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com)

Cheers,  
Ben

On Sat, Nov 2, 2013 at 12:22 AM, Ting Wu \<

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**Author:** ![Ting\_Wu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/3bc359/32.png) [@Ting\_Wu](https://www.ruby-forum.com/u/Ting_Wu)\
**Post date:** [November 6, 2013, 1:14am UTC](https://www.ruby-forum.com/t/resolution-of-usrp-n210-and-n200/237273/3 "2013-11-06T01:14:39Z")

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Hi Ting -

Sorry, there really wasn’t a good reason for me to not answer your  
question, regardless =)

So the ADCs are indeed 14 bits, but those samples go through a lot of  
processing on a number of different platforms, and get sent over a few  
different buses. At any of these stages, depending on your system  
parameters, there might be conversions and scaling factors applied to  
the  
data, which changes the representation. Remember that since the ADC is a  
14-bit ADC, you are never really getting more precision than those  
14-bits;  
they are just different ways of representing that data.

Does that help, at all?

Cheers,  
Ben

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**Author:** ![Ting\_Wu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/3bc359/32.png) [@Ting\_Wu](https://www.ruby-forum.com/u/Ting_Wu)\
**Post date:** [November 6, 2013, 6:23pm UTC](https://www.ruby-forum.com/t/resolution-of-usrp-n210-and-n200/237273/4 "2013-11-06T18:23:29Z")

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To add to what Ben has wrote, if decimation is involved in the  
processing  
stages it is possible to get a higher resolution than that of the  
initial  
samples. For example, a decimation by a factor of two can increase the  
bit  
precision by one. So in this case, it could depend on where the  
interface  
is being defined. Perhaps the ADC chips being used are indeed 14 bits,  
as  
per the spec sheet, but the implementations of the different LFRX  
versions  
may have different post-ADC processing stages. If this is the case,  
while  
the precision of the ADC chips is 14 bits, the output of the LFRX could  
have a higher resolution.

For those wanting to learn more, this is the principle behind  
sigma-delta  
ADCs [http://en.wikipedia.org/wiki/Delta-sigma\_modulation](http://en.wikipedia.org/wiki/Delta-sigma_modulation).