[USRP-users] USRP Calibration Routine

Jason Abele jason at ettus.com
Wed Apr 4 17:52:14 EDT 2012


On Wed, Apr 04, 2012 at 12:04:53PM -0400, Dan CaJacob wrote:
> Hi Josh,
> 
> In some of the documentation for the three calibration utilities, you
> have indicated that the RF ports on the daughter-card being
> calibrated should be disconnected.  I have always done that, but I
> was wondering if 50 Ohm terminations on the connectors would be of
> any benefit?  Thanks.

It won't hurt anything, but I doubt it will change much.  The most
likely change would be in RX DC/LO which is not statically calibrated,
instead, it is handled by an average and subtract operation in the FPGA.

During cal, the TX is switched away from the TX antenna into the
"closed" switch port, where it leaks into the RX which is listening to
the TX/RX antenna.

So termination on RX2 should have no effect as that port is already
unused in calibration.

However, the calibration code is open-source and there is no real reason
you can't experiment with other configurations or use the concepts
within it to fit the calibration routines to your application/system
design.  It is important to note that transmitting close to full-power
directly into the receiver is likely to result in hardware damage, so
be careful of your settings and power-levels if you modify the
calibration routines.

Jason



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