trans-receiver system using PXI

[Sharmi]

Hi,

I need to build a trans-receiver system using PXI. For the transmission part I can use a PXI 5652 to generate a single tone continuous waveform. 

For the receiver part, I need an antenna to capture the signal transmitted by 5652 (which will have a transmission antenna ). The received signal will then be down converted by PXI 5601 (RF OUT of 5652 is connected to LO IN of 5601). The intermediate frequency will be then digitized by PXI 5622 (IF OUT of 5601 is connected to IF IN of 5622). 
But my question is these connections are already there between the slots/chassis.(The next stage has I/Q demodulation but I want to get clear on this part first). But there is not output port on the PXI 5622, so how can I check the digitized output?

 I have attached a file for reference.

Thanks,
Sharmi

[Sharmi]

Hi,

I need to build a trans-receiver system using PXI. For the transmission part I can use a PXI 5652 to generate a single tone continuous waveform. 

For the receiver part, I need an antenna to capture the signal transmitted by 5652 (which will have a transmission antenna ). The received signal will then be down converted by PXI 5601 (RF OUT of 5652 is connected to LO IN of 5601). The intermediate frequency will be then digitized by PXI 5622 (IF OUT of 5601 is connected to IF IN of 5622). 
But my question is these connections are already there between the slots/chassis.(The next stage has I/Q demodulation but I want to get clear on this part first). But there is not output port on the PXI 5622, so how can I check the digitized output?

 I have attached a file for reference.

Thanks,
Sharmi

[Sharmi]

Could anyone please help me on the above problem ?

Thanks,

Sharmi

[Sarah_Y]

Hi Sharmi,

Are the cards you showed in your document the only ones you have available to you or do you have another 5652 by chance?  

The NI 5663 vector signal analyzer is made up of 3 PXI cards--the 5601, 5652, and 5622.  The 5601 receives an RF signal through the RF IN connection.  It then downconverts the signal to a lower frequency using mixers.  The frequency of the mixers are controlled by an external local oscillator, the 5652.  You cannot use the 5601 without an external LO source such as the 5652.  After the signal has been downconverted, it is then sent to the 5622 to be digitized.  Once the signal is digitized, the data is sent across the PXI backplane to the PXI controller and can then be collected using LabVIEW or the RFSA Soft Front Panel.  

The NI 5673 vector signal generator is also made up of 3 PXI cards--the 5611, 5652, and 5450.  To generate a signal, a bitstream is generated using LabVIEW, sent across the PXI backplane to the 5450.  The 5450 converts it from a digital signal to an analog signal, sends it to the 5611, and the 5611 upconverts the signal to an RF frequency.  The 5611 upconverts the signal using mixers and the frequency of the mixers is controlled by an external LO, the 5652.

I am a bit confused how you are communicating with your PXI system since your drawing shows 1394 and GPIB.  What is your PXI controller?  You should be able to use the NI-RFSA and NI-RFSG drivers to control the hardware.

[Sharmi]

Hi Sarah,

Thanks for the reply.

We have a vector signal analyzer with 5652, 5601 and 5622, a vector network analyzer with 5630 and a vector signal generator with 5450, 5611 and 5652 like you said.

Please ignore the 1394 and GPIB, which are part of the previous implementations not in PXI. Sorry for the confusion.

Below are my further questions

• Is the data, after it is down converted and digitized by the 5622 is automatically sent to 5450?
• 5450 has “400 MS/s I/Q Signal Generator” written on it, so does it generate I and Q channel data separately?
• Also 5611 has “I/Q Vector Modulator” written. So, can it demodulate a signal (after it is split into I and Q components by 5450) and then combine the resultant output?

Sorry for too many questions.

Thanks so much,

Sharmi

[Sarah_Y]

Hi Sharmi,

To address your questions:

• Is the data, after it is down converted and digitized by the 5622 is automatically sent to 5450?

No, the data is not automatically sent to the 5450.  The digitized data is sent to the backplane and can be accessed on your controller/laptop through LabVIEW or the RFSA Soft Front Panel.  The 5450 is used to take digital signals generated by LabVIEW and turn them into an analog signal.  It is not used in any part of the downconversion process.  

If you want to take the data that you receive from your 5663 VSA and send it to your 5673 VSG, you will need to do so using software.  There are RFSA and RFSG examples that ship with the driver that you can use as a starting point on how to acquire a signal and send a signal using LabVIEW.  These examples can be found by going to Start » All Programs » National Instruments » NI-RFSA (or NI-RFSG for generation examples) » Examples.

• 5450 has “400 MS/s I/Q Signal Generator” written on it, so does it generate I and Q channel data separately?

The 5450 does generate IQ data on 2 separate channels.  LabVIEW is used to generate an IQ bit stream.  The IQ data is combined after being upconverted with the 5611.

• Also 5611 has “I/Q Vector Modulator” written. So, can it demodulate a signal (after it is split into I and Q components by 5450) and then combine the resultant output?

The 5611 is an upconverter and is used to take the IQ signals generated by the 5450, combine them, upconvert them from some IF frequency to an RF frequency and transmit them.  It can be used to do some basic types of modulation, but not demodulation.  The NI RF Signal Generators Help ( Start » All Programs » National Instruments » NI-RFSG » Documentation) has a section about the 5611 that includes the hardware block diagram and a more detailed explanation about each part of the block diagram.  This is where you can find out more about what basic types of modulation the 5611 is capable of performing.

Let me know if you have more questions, I'd be happy to help.

[Sharmi]

Hi Sarah,

I have looked into RFSG examples like RFSG Single Tone Generation (since we have 5652 I could execute the continuous waveform example only). I also went through RFSA help to learn how to configure RFSA through soft front panel.
I learnt that RF OUT on 5652 can be connected to RF IN on 5601 to view the waveform in RFSA soft front panel. What if I want to view the digitized data RFSA on as well? I did not find an output port on 5622 from where I could take the  digitized output.

Also we have only niRFSG folder in Start » All Programs » National Instruments » NI-RFSG » Examples. I went through some of them but I don't know which example tells us about acquiring data from RFSG in RFSA and pass that digitized data to 5450.

Could you please tell me which examples to look for in order to access the digitized data from 5622 in  to 5450.

Thanks so much,

Sharmi

[Sarah_Y]

Hi Sharmi,

I think I am a bit confused on what your overall application is and what you are trying to do with these devices.  Could you explain what your end goal is and the system that you need?  Are you trying to read in a signal with your receiver and then transmit the received signal?  

RFSG stands for RF Signal Generators and RFSA stands for RF Signal Analyzers.  So you will not acquire data from an RFSG device, only from RFSA devices.  If you want to transmit the signal that you receive from your RFSA, you can try combining example to write the waveform you acquire with your RFSA to the RFSG device.  I attached some code that you can take a look at.  It may or may not be what you need for your application.

When you view the data from the RFSA device in the soft front panel, you are viewing the digitized data from that device.  There is not an output port of the 5622--all of the digital data is sent to the PXI backplane.  You then need to use your laptop/PXI controller to access the data using software.  You can use an RFSA example to gather the digital data on your computer. 

[Sharmi]

Hi Sarah,

Sorry if I confused you.

I have made a flow chart kind of thing with bullet points for my project below

• Transmit an microwave signal (5652 of VSG 5673) via an antenna
• Receive the modulated signal with an antenna to down-convert into IF frequency (5601 of VSA 5663)
• Since the received signal is modulated, we need to demodulate the same using IQ demodulation technique (we have 5611 which you said cannot be used for demodulation, so do we need another component to demodulate the signal?)
• Re-transmit the signal via VSG.

I need to pass the signal received by VSA (5601) for subsequent demodulation after down conversion. To do this, do I need to write the waveform once I acquire in VSA?

(when I said “about acquiring data from RFSG in RFSA”, I meant waveform generated by RFSG and viewed in RFSA. Sorry if it was not clear.)

Thanks so much,

Sharmi

[Sarah_Y]

Hi Sharmi,

Thanks for the clarification.  Hopefully I can help answer your questions better now.

Part 1:  Transmitting the signal

• Using the 5652 should work fine if you just need to send out a sinusoidal wave.  If you need to modulate the signal that you are sending out, I would recommend connecting the 5652 to the 5450 and the 5611 to have the full 5673 VSG configuration.  Using these 3 cards together will allow you to send out more complicated modulated signals to your antenna.  The 5652 can send out a sin/cos wave and perform OOK and FM modulation, but that's all.

Part 2:  Receiving the signal

• The signal from your antenna is going to go into the RF IN port of the 5601, which is also connected to a second 5652 as well as the 5622 to for a 5663.
• The signal is going to be downconverted from an RF signal and digitized, then sent to the backplane of the PXI chassis.  Then you can use LabVIEW to collect the data.  When the digitized signal is read back in with LabVIEW, you can read either the IQ signal, or a power spectrum of the signal
• The 5601 along with the 5622 will downconvert the RF signal as well as split it back into IQ pairs

Part 3:  Demodulating the signal

• After the signal is in LabVIEW, you can manipulate the digitized data to demodulate it
• The example I attached to my last post should be a good starting point for how to send the data back to your VSG to be transmitted after it is received with the VSA

Questions for you:

• Were you planning on using hardware to demodulate the signal?
• What type of modulation are you using?

[Sharmi]

Thank you so much Sarah for the last post and the example. They helped a lot. Now I have an idea of the data flow in the system. 

 I downloaded and looked into the example in my laptop but I need to have the example in the PC which is connected to PXI. However,if I go to Start » All Programs » National Instruments » NI-RFSA » Examples, I don't see any Labview examples for RFSA. But there is a folder on NI PXI 5660 under niRFSA which has Labview examples like "ni5660 Demodulate AM" and "ni5660 Demodulate FM". I guess I need to copy the RFSA examples in this system.

Also in Start » All Programs » National Instruments » NI-RFSG » Documentation, it says that the documents aren't there in this release.

For the questions 

• The transmitter only needs to send a continuous waveform which will be modulated by external sources, not part of this PXI.
• I need to apply a Digital Quadrature Demodulation technique to demodulate the signal.

Thanks so much,

Sharmi