[USRP-users] 10 MHz reference signal on B210

mleech at ripnet.com mleech at ripnet.com
Tue Oct 3 11:52:44 EDT 2017


You'd have to look at the detailed specs of the ADF4001 PLL chip that is
used to steer the VCTCXO. 

That chip doesn't, as far as I know, have a "reference quality metric"
output, and if it does, UHD doesn't expose it. 

On 2017-10-03 11:44, Dario Fertonani via USRP-users wrote:

> I'm testing the behavior of B210-based systems, comparing the performance with "internal" and "external" (10 MHz) clock source. Expect for the following "is the 10 MHz input actually present" check running when the app starts, the two branches share the same code. 
> 
>> rfBoardPtr->set_clock_source( "external" ); 
>> sleep( 2 );//give board time to lock 
>> if ( rfBoardPtr->get_mboard_sensor( "ref_locked" ).to_bool( ) == false ) 
>> { 
>> throw std::runtime_error( "Unable to find a valid 10 MHz reference signal. Please check that the signal source is properly plugged in." ); 
>> } 
>> rfBoardPtr->set_time_unknown_pps( 0.0 );
> 
> Besides that check, is there a way of measuring the quality of the signal via (UHD) software API, ideally in a more granular way? The check above "passes" even when the input signal is poor, which I see by validating through external instruments the quality of the radio signal emitted by the board. Ideally, I'd want an API that tells me about such problems before I actually check the radio output. To be clear, these are relatively-minor radio issues, but are sufficient to reduce the DL peak rate of my LTE system from 150 Mbps to 50-100 Mbps with respect to a fully-functional board (either fed by "internal" clock source, or by a proper 10 MHz source). The quality of the radio output varies noticeably (at least when measured with advanced full-stack metrics) when I change the amplitude of the 10 MHz reference, which is surprising since said changes are within the recommended range of the 10 MHz reference. Could someone please confirm said specs, in terms of (peak-to-peak) amplitude
and waveform (square, sine, ...)? 
> 
> Thanks, 
> Dario 
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