Re : Bad level on NI RFSA front panel with 5663

[Choubahulk]

Hello,

We own a PXIe-1075 chassis equiped like this :

Slot 1: PXIe-8108 “embedded controller”

Slot 2: empty

Slot 3: empty

Slot 4: empty

Slot 5: PXI-5650 RF Generator                   

Slot 6: PXIe-5601 RF Down converter       

Slot 7: PXIe-5622 16bits digitizer               

Slot 8: PXIe-5622 16bits digitizer

Slot 9: PXIe-5622 16bits digitizer

Slot 10: empty

Slot 11: PXIe-5622 16bits digitizer

Slot 12: PXIe-5622 16bits digitizer

Slot 13 to 18: empty

Slot 5 – Slot 6 – Slot 7 are coupled to form a Vector Signal Analyzer NI-PXIe-5663

If I want to use rapidly the NI-PXIe-5663, I open NI RFSA front panel, I use an external RF generator that give me CW waveform (500MHz for example) at 0dBm.

So I get this CW waveform on NI RFSA at 500MHz front panel but the level is -40dBm. So I don’t understand why?

So before this, I have test each board separately except the Down converter .I mean PXI-5650 RF Generator and PXIe-5622 16bits digitizer.

Spectral analyze of PXI-5650 RF Generator (tested with NI RFSG front panel) give me the right frequency and the right level, PXIe-5622 16bits digitizer (tested with NI SCOPE front panel displays the right frequency and the right level of an external RG generator.

But I don’t known how to test PXIe-5601 RF Down converter only.

On MAX each board test is right.

Depending on our applications we coupled or uncoupled boards of 5663.

We use LABVIEW 2011 with all update done

Would someone help me to understand this difference of level on NI RFSA front panel?

Best Regard

Choubahulk

[Aurel.Co]

hi Choubahulk!!

Did you respect that your Ref level > Max level signal?

Usually Ref level + 10Dbm = Max level signal.

Best regards

[Choubahulk]

Hello Aurélien

Thank you for your answer

I think we don't understand each other . On NI RFSA front panel you can't set up Ref level ,because NI RFSA use NI PXIe 5663 to display results as spectrum analyzer.

I attach 3 pics:

- the signal supplied by my RF generator

- spectrum analyze of this signal

- the signal on NI RFSA front panel

Ni RFSA and NI PXIe form a spectrum analyzer ,so I think that I had to find the same result like on a real spectrum analyser

Would you tell me ,what do you think about this situation?

Best regards

Choubahulk

[Choubahulk]

Hello,

I think I found my problem but I need confirmation!

I said that NI-PXIe 5663 must give the same results as a stand alone spectrum analyzer.

Or if I want to analyze a CW signal as such frequency= 500MHz 0dBm, a stand alone analyzer displays the same signal minus cable attenuation and the NI-PXIe5663 displays a CW signal such as frequency=500MHz and a level of -40dBm.

So the only thing that I must verify is input matching on PXIe-5601 RF Down converter           .

If  I place an attenuator on the input on PXIe-5601 RF Down converter ,the NI-PXIe5663 displays a CW signal such as frequency=500MHz and the level value  is the value of the attenuator  plus the cable attenuation.

So my conclusion is that the input of input matching on PXIe-5601 RF Down converter is mismatched.

To verify the input impedance, can I place a Vector network analyzer to measure S11?

Or is there another manipulation to confirm this?

On MAX when I control the state of each module, is input impedance controlled?

Would someone help me?

Best regards

Choubahulk