[USRP-users] Possible Causes of This Spurious Signal?

Kyeong Su Shin ksshin at uw.edu
Wed Jul 26 10:52:52 EDT 2017


Hello,

I observe a spurious signal in the PSD estimates that are obtained using a
USRP, which I cannot identify the cause. Could someone help me identifying
the cause of this?

Plots are shown below.

*Hardware*:
-USRP N200 r4 + UBX-40 v1
-Agilent FieldFox SA, as the reference.

*Software*:
-Windows Server 2012
-UHD 3.9.3
-GNURadio 3.7.10.1

..and also on a UHD-based (non-GNU Radio) spectrum scanner script that I am
working on.

*Setting*:
Gain : 0
lo offset : 0
Samp rate : 25MS/s (100e6/4)
Antenna: RX2

*The Spurious Signal:*

@ fc = 641.25 MHz (reproducible at 642 / 641 MHz)

​
Goes away @ fc = 630MHz.

​
*+- 25MHz*:

No, I don't see any signal that could get aliased; I believe this is not
due to the aliasing from the DDC.



​
*1/2 fc (315MHz):* Clean (no signal observed).


​

Regards,
Kyeong Su Shin
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