# Is it possible to read the ADC samples before the downconversion from the USRP?

**URL:** <https://www.ruby-forum.com/t/is-it-possible-to-read-the-adc-samples-before-the-downconversion-from-the-usrp/222163>\
**Category:** GNU Radio\
**Created:** [August 15, 2012, 6:39pm UTC](https://www.ruby-forum.com/t/is-it-possible-to-read-the-adc-samples-before-the-downconversion-from-the-usrp/222163 "2012-08-15T18:39:34Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\
**Post date:** [August 15, 2012, 6:39pm UTC](https://www.ruby-forum.com/t/is-it-possible-to-read-the-adc-samples-before-the-downconversion-from-the-usrp/222163/1 "2012-08-15T18:39:34Z")

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Hi,

I want to collect the samples of the USRP at the IF instead of the  
baseband, so is there any way to read the ADC samples directly without  
downconversion, at the PC?  
I do not want to touch the FPGA.

–

Alex,  
_Dreams can come true just believe._

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**Author:** ![akeem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/54ee81/32.png) [@akeem](https://www.ruby-forum.com/u/akeem)\
**Post date:** [August 15, 2012, 6:53pm UTC](https://www.ruby-forum.com/t/is-it-possible-to-read-the-adc-samples-before-the-downconversion-from-the-usrp/222163/2 "2012-08-15T18:53:00Z")

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There is generally no IF on a USRP: it’s all baseband, even at the ADC.  
That said, you need decimation in order to fit the full-speed baseband  
data  
over the 1Gbit (or USB) link. There is an existing user FPGA  
modification  
somewhere that buffers full-speed baseband data into the SRAM on an N210  
for later retrieval. What exactly are you trying to do?

–n

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<div class="post-metadata">

**Author:** ![akeem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/54ee81/32.png) [@akeem](https://www.ruby-forum.com/u/akeem)\
**Post date:** [August 15, 2012, 9:25pm UTC](https://www.ruby-forum.com/t/is-it-possible-to-read-the-adc-samples-before-the-downconversion-from-the-usrp/222163/3 "2012-08-15T21:25:32Z")

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In short, I want to get the samples right after the ADC, without any  
down-conversion, decimation, and filter, etc.

On Wed, Aug 15, 2012 at 11:52 AM, Nick F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > Hi,
> > 
> > * * *
> > 
> > USRP-users mailing list  
> > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> > [http://lists.ettus.com/mailman/listinfo/usrp-users\_lists.ettus.com](http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com)

–

Alex,  
_Dreams can come true just believe._

---

<div class="post-metadata">

**Author:** ![akeem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/54ee81/32.png) [@akeem](https://www.ruby-forum.com/u/akeem)\
**Post date:** [August 16, 2012, 2:54pm UTC](https://www.ruby-forum.com/t/is-it-possible-to-read-the-adc-samples-before-the-downconversion-from-the-usrp/222163/4 "2012-08-16T14:54:22Z")

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Exactly what I want, thanks!

On Wed, Aug 15, 2012 at 2:48 PM, Josh B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > > That said, you need decimation in order to fit the full-speed baseband
> > > 
> > > > _Dreams can come true just believe._
> 
> [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> [http://lists.ettus.com/mailman/listinfo/usrp-users\_lists.ettus.com](http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com)

–

Alex,  
_Dreams can come true just believe._