RFSA generates internal interferring signal

[LVFan]

I'm evaluating the PXI-5660.
When I use the RFSA Demo Panel to examine the spectrum, I can see multiple single frequencies, even if I terminate the RF input with 50ohms (see attached file). Even if I changed the CF the picture is the same (peak by CF, CF+14Hz, CF+46,8MHz). If I change the attentuation from 20dB to 0dB the signals are increased correspondingly.
Therefor, I think these disturbing peaks were generated internal by the LO's.
I'm not sure if this is normal, but selfcalibration and selftest returns no error.

Is it possible to suppress these peaks by adjusting the filter and attentuator settings.

(Following my HW/SW-configuration:
PXI1000B
PXI5610+PXI5441=RFSG
PXI5600+PXI5620=RFSA
RFSG-Driver1.1.0
RFSA-Driver1.5.0
MT3.0
SMT1.1)

PS.: The RF input has an inscription "0V DC max". Does this mean as a precaution I have to use a DC-blocker against damage by DC signals.?

[Watermann]

hello LVFan,

if the peaks are the same for every measurement I think a filter would do the job. but for the fact I never have done anything with your software nor rfsa or rfsg I could only provide you this link.
sorry, hope there is anyone who could help you more...

greets!

[JSflow]

I'll post my message here as well, since I'm having a similar issue.

I havn't connected anything to the RFSA's input, but as you can see from the
captured image of RF SoftFrontPnel, there are very high peaks in between
7MHz to 17MHz. Also, due to this, I get Signal Overload!!!

Here are my settings:
cf: 12MHz
span: 10M
rbw: 10k
ref level: 10 dBm


Thanks

[JSflow]

I have another screenshot that shows when the Ref level changes to
40 dBm. (when other settings remain equal)
It still shows "Signal Overload".

I don't see this behavior at any other frequency.

[Andy_Hinde]

Hello JSFlow and LVFan,
I believe you are experiencing different behavior so let me respond to you both here:

JSFlow,
Your screenshot looks like it is exhibiting the behavior for which we include a Note to Users in the current 5660 shipping kit. I will post this to this thread. The behavior should not be present when you tune the 5660 to 20 MHz or above. When you are < 20 MHz, the settings indicated by the note to users should correct the issue. Can you verify this to be the case and also try the proposed settings for the < 20 MHz use case?

LVFan,
Have you tried moving the 5660 to different slots in the PXI chassis? The only reason I ask this is to help determine if the culprit here is indeed the 5660. If you can move the unit around and see the exact same behavior, then the behavior you are seeing is out of spec and the HW you are using for evaluation purposes is not delivering the same performance as a fresh production unit would.
If this ends up being the case, I would contact your local NI sales rep and inform him of this and National Instruments will get you a better unit for evaluation. Please let me know if you need help.

Regards,
Andy Hinde
RF Staff Product Support Engineer
National Instruments

[abedi]

Bonjour,

J ai aussi un probleme similaire, a l entree NI 5600 je connecte un antenne qui fonctione a 900Mhz/2000Mhz, mais en utilisant le demosRFSA, je n obtiens aucun pick en sortie(regardez l image ci-dessous),.

je ne comprends pas pourquoi?

Merci pour vos suggestions.

[abedi]

Bonjour,

J ai aussi un probleme similaire, a l entree NI 5600 je connecte un antenne qui fonctione a 900Mhz/2000Mhz, mais en utilisant le demosRFSA, je n obtiens aucun pick en sortie(regardez l image ci-dessous),.

je ne comprends pas pourquoi?

Merci pour vos suggestions.

[Andy_Hinde]

Hello Abedi,
Unfortunately I don't speak French, so is there a way you can post a translated version of your question?

Thanks,
Andy

Message Edited by Andy Hinde on 08-04-2005 01:03 PM