On 03/24/2021 05:10 PM, Jerrid Plymale wrote:
The devices are operating using direct connection via coax cables.
You absolutely need to put a 30dB attenuator in-line to prevent RX
destruction in the case of "ooops" moments from setting the TX
power output too high.
The target frequency is 1.57542 GHz, and our current bandwidth is 4
MHz. We will need to increase the bandwidth to 20 MHz soon for further
system development.
The TX and RX gain are maxed on the receiving hardware. The TX gain of
the transmitting hardware is set to 0, as at max the noise strength
increases to ~ 20 dB.
Attached are images of the FFT provided by the Frequency Sink in
Gnuradio. Hopefully these give a visual aid for the problem at hand.
When I have the transmitter USRP turned off (image 1), it would seem
like the noise floor coming into the USRP is around -94 dB. When the
transmitter is turned on and the flowgraph is started with the
transmitted signal muted (I am using a python block with code to
create custom signals that is then connected to a mute block that then
connects to the UHD USRP sink block to be able to mute the signal
during runtime), the noise floor increases to around -78 dB.
Best Regards,
Jerrid
You are likely just seeing the LO leakage, along with the inevitable
phase-noise curve of the LO.
*From:* Marcus D Leech <patchvonbr...@gmail.com>
*Sent:* Wednesday, March 24, 2021 11:58 AM
*To:* Jerrid Plymale <jerrid.plym...@canyon-us.com>
*Cc:* USRP-users@lists.ettus.com
*Subject:* Re: [USRP-users] Strong noise added to signal transmitted
by X310 with a UBX 40 daughterboard
Is the j B is over-the-air or direct connection?
What frequency? Bandwidth?
Do you have TX and RX gain turned all the way up?
Can you share your flow-graphs, or minimum
Graphs that show the problem?
Sent from my iPhone
On Mar 24, 2021, at 12:20 PM, Jerrid Plymale
<jerrid.plym...@canyon-us.com
<mailto:jerrid.plym...@canyon-us.com>> wrote:
Hello All,
I have been running tests in which I am transmitting a signal from
one USRP X310 that’s using a UBX 40 daughterboard, and that signal
is being received by another USRP X310 using a UBX 40
daughterboard. I have noticed that when I have the receiving USRP
running with the Gnuradio flowgraph active, as soon as I start the
transmitting USRP’s Gnuradio flowgraph, there is a jump in the
noise floor as it is seen by the receiving USRP, and its roughly a
14 dB increase. This occurs even if I have the signal being
transmitted muted. Does anyone have any idea what the source of
this added noise could be? It is something that I need to mitigate
as much as possible for the tests I am running using these USRPs.
Any feedback will be greatly appreciated, thanks!
Best Regards,
Jerrid
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