[USRP-users] ADC signal level

mleech at ripnet.com mleech at ripnet.com
Fri Sep 12 10:03:03 EDT 2014


-15dBm -- don't confuse the dBFS that your FFT routines, or Gnu Radio
gives you with the actual signal level at the antenna connector. 

You'll have to determine the range experimentally, since it varies over
frequency and gain setting and also device to device. 

 When the magnitude of the signals are approach 1.0 (when using
floating-point on the host side) then you know you have 

 approached saturation in the ADC. 

On 2014-09-11 23:54, Sam mite wrote: 

> Thanks for the response. So you are suggesting that input at the USRP WBX input should never exceed -15dB? Also, I want to know the input signal levels (extremes) to WBX for which :
> * Peak of the Signal is deriving the ADC into saturation .
> * Peak of the Signal is touching minimum level that can be sampled by ADC. 
> On Thu, Sep 11, 2014 at 11:20 PM, <mleech at ripnet.com> wrote:
> I think the reference level is set to about 2VP-P, and with 14 bits I'd guess about 120uV as the minimum input level. 
> But you're going to be limited to about -15dBm at the input plane to the WBX, regardless of what you set the gain on the WBX, unless you 
> have attenuation in front to limit signals to less than about -15dBm, to prevent damage to the LNA. 
> On 2014-09-11 13:56, Sam mite via USRP-users wrote: 
> I am thinking of putting an AGC in front of USRPN210 with WBX. I know that N210 ADCs have dynamic range of 84dB (14bit ). I am going to set rx gain of WBX at 0. I want to know that what are maximum and minimum signal level that should be present at the input of N210 ADC to use its full dynamic range as well as avoid saturation ? 
> -- 
> Regards,
> Sam 
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