[USRP-users] SBX Tx output power and Sample rate question

[Baokun Liu]

Hi all,

I am playing with USRP N210 and SBX daughterboard using Gnuradio Companion.
I have two questions here.
1) SBX could give us a TX output power of 16 to 20dBm, and 32dB power
control range. Does that mean the maximum TX output power is about
52dBm? If I use USRP for radar application, what's maximum detection range
approximately?
2) USRP could provide 25MHz maximum bandwidth with 16 bit I/Q samples. Does
this mean the maximum sampling rate I can set is 25MHz when I use USRP for
transmitting a complex signal?The complex signal should have a bandwidth
smaller than 25MHz?

Thanks,

Baokun

[Marcus D. Leech]

Post by Baokun Liu
Hi all,
I am playing with USRP N210 and SBX daughterboard using Gnuradio
Companion. I have two questions here.
1) SBX could give us a TX output power of 16 to 20dBm, and 32dB power
control range. Does that mean the maximum TX output power is about
52dBm? If I use USRP for radar application, what's maximum detection
range approximately?
2) USRP could provide 25MHz maximum bandwidth with 16 bit I/Q samples.
Does this mean the maximum sampling rate I can set is 25MHz when I use
USRP for transmitting a complex signal?The complex signal should have
a bandwidth smaller than 25MHz?
Thanks,
Baokun

The maximum output power is in the 17-20dBm range. The minimum is
(17-20dBm) - 32dB == (-15dBm to -12dBm). A power level of 52dBm would
be about 120 watts out. None of our cards produce anything above
about +20dBm. And if you add amplifiers, you must remember to stay
legal within your region of jurisdiction--it's up to you to
investigate, comply, and acquire any required licenses.

The SBX daughtercard has a noise figure of about 5dB, depending on
frequency chosen. The noise figure of the receiver is one of a large number
of parameters that can help you determine what the performance of
your radar system will be. There's no way anyone can honestly give you
a number like "what is the maximum range I can expect from my radar
system" without having a lot of parameters "filled in", and a lot of
"hand waving".

Yes, 25Msps == 25Mhz bandwidth. Your I/Q signal should be, ideally, no
larger than about 80-85% of that.

[Dan CaJacob]

20 dBm is the maximum power output, period. To achiev this, the
tx-amplitude would have to be maxed (1.0) and the tx-gain would also have
to be maxed (31.5 dB?). Of course, your signal would be very nonlinear at
those levels. Stick to tx-amplitude below, or up to 0.2 and then you can
vary tx-gain as you wish.

Very Respectfully,

Dan CaJacob

Post by Baokun Liu
Hi all,
I am playing with USRP N210 and SBX daughterboard using Gnuradio
Companion. I have two questions here.
1) SBX could give us a TX output power of 16 to 20dBm, and 32dB power
control range. Does that mean the maximum TX output power is about
52dBm? If I use USRP for radar application, what's maximum detection range
approximately?
2) USRP could provide 25MHz maximum bandwidth with 16 bit I/Q samples.
Does this mean the maximum sampling rate I can set is 25MHz when I use USRP
for transmitting a complex signal?The complex signal should have a
bandwidth smaller than 25MHz?
Thanks,
Baokun
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