PXIe-5663e block diagram

[HansAnders]

Hello,

I have a question regarding the block diagram of the VSA 5663e, in particular of the 5601 RF Downconverter (see attached file).

There is an amplifier that can be switched on, but I can't find any means of controlling this PA manually. Is it meant to be a preamplifier?

Is this PA switched on automatically by software? If yes, under what conditions? There seems to be no way to retreive the status of the PA from the instrument.

Thanks

[RamonaL]

HI HansAnders,

the only thing you can direclty set is the reference level. You should use the smallest possible level you can (depending on your signal).

Than you have the possibility to change some other settings, so the amplifier will be turned on (or off). I have here two documents which explains how to do that:

Attenuation of the 5663

Downconverter Gain

Unfortunatly I dont have any information about when it is turn on exactly. So this you will have to try. But you will see when you set the attenuation on manual and to zero your noise will be reduced.

I hope this helps,

RMathews

[RFguy001]

Hello RMathews,

thanks for your reply.

The Downconverter Gain seems to refer to the overall system gain of the downconverter module, including all amplifier gains and RF attenuators. I see no jumps in the gain or attenuator value that would indicate a switching of the amplifier. Also if I read the mixer level property, it seems to be  Reference Level minus RF Attenuation. No hint of an additional gain. Coming from low reference levels, switching the amplifier (with a fixed gain) would first increase the attenuation by a large amount to have the same over all gain. But this I ddon't see.

The reason I'm asking about the amplifier switching is that I want to do intermodulation measurements. And an amplifier in the signal path would drastically change the overall TOI of the analyzer and this I would need to know.

Best regards

[RamonaL]

Hi,

well, the thing is that there is no way to change this settings manually. All is done by the driver.

The only thing you can do is working with the RF attenuation and modify it online (while measureing your data), to see what the perfect value for your mesaurement is. The only way is to test it.

Sorry, that I cant tell you any better news.

RMathews

[Anckit]

HansAnders,

I reiterate what RMathews already said in their reply, that the amplifier in the RF Chain cannot be controlled by the user directly.

NI-RFSA driver defines the RFAttenuation = 0 state for PXIe-5601 or PXIe-5663/5663E as all RF Attenuator set to 0 and the RF Amp enabled. Changing between RF Attenuation = 0 and RF Attenuation = a large number, say 20 dB (the RF Amp provides 16 dB of nominal gain) would cause the amplifier switched in and out. Note that this amplified is NOT the first amplifier in the chain and hence the noise floor may not be determined by it. Again since this is not the first Amplifier in the chain, it is NOT referred to as the Preamp nor can be controlled by the Preamp Enabled attribute. Hope this brings more clarity.

If you have more follow up questions, please feel free to post them on this forum.

Thanks,

Anckit Wadhwa