Re: [Discuss-gnuradio] Need info regarding USRP Front End protection/vulnerability

[Matt Ettus]

On 01/27/2010 03:53 PM, William L. Bahn wrote:
> We will be using the USRP in an environment where it will be engaged by
> an Electronic Attack system capable of putting out about 40MW of EIRP in
> the form of pulses that are on the order of 4ns (possibly longer) but
> with very fast rise times on the order of 500ps. Our system will be
> using just the simple vertical whip antennas sold by Ettus. We are
> looking at using pretty much all of the Flex series of daughterboards
> and possibly the XCVR2450 and WBX boards as well.
>
> What I need to determine is what the maximum power is that can be
> present at the antenna in order to avoid damaging the front end so that
> we can determine the minimum range to the jammer during the exercise.
>
> Thanks.


Wow... that's a lot of power.  In any case, the parts are all spec'ed in 
terms of maximum CW input power, so you'll need to take into account 
center frequency, pulse width, duty cycle, duration of test, bandwidth 
of your filters, etc.

Based on the part datasheets, the absolute maximum input power for the 
RFX boards is -10dBm.

The chip in the XCVR2450 specs +10 dBm.

For the WBX it will depend on your gain setting.  At maximum gain it 
will be -15 dBm, and at minimum gain it is about +15 or +20 dBm.  If you 
remove the small granddaughterboard, you'll lose about 18 dB of gain but 
would have a higher safe input power of nearly a watt as long as you 
have the maximum attenuation set.

You can probably exceed these for brief periods, but I'm not sure, as 
I've never tried anything over -10dBm on any of these boards.  Please 
let me know how this goes for you!

Matt