Frequency Modulation using RFSG NI PXIe 5654

[aLAM73]

Hi,

I'm trying to use RFSG NI PXIe 5654 to generate a pulsed frequency modulated signal at 1.2GHz center frequency. Following is my test setup:-

1. FM Modulating Signal (A DC Voltage in my case) from a function generator which generates a pulsed DC Voltage.

1 a. The RFSG settings are as follows :

a. Pulse on  b. Modulation : FM, Wideband, Sensitivity : 100 % , DC Voltage : 870mV

2. The pulse signal and the FM Modulating Signal (mentioned in point 1) are fed to RFSG 'Pulse in' & 'FM in' port.

3. RF out signal is connected to RFSA NI PXIe 5665 VSA. The spectrum is monitored on a RFSA soft Panel.

4. For test purpose, when I feed in a pulsed DC voltage (FM Modulating Signal) to RFSG, it generates a bandwidth as shown in the picture below. whereas I expected a " tone shifted from the center frequency " as shown in picture below.

5. I have tried the same on Agilent E4428C ESG Analog Signal Generator  and found the results as expected.

Modulating SignalRFSG Actual ResponseRFSG Expected REsponseRFSG Configuration

         Kindly guide if I'm configuring the device in correctly or is there any issue / limitation.

[WillyWad]

aLAM73,

It sounds like you have the RFSG settings configured correctly.

What are you doing to generate the signal in the image "RFSG Expected Response"?

-Will

[aLAM73]

Hi,

   Actually the final output which I want is a Linear Frequency Modulated Pulse. For that I would have to give the "FM Modulating Signal" in the form of a pulsed linear ramp and adjust the sensitivity of RFSG to get the desired Bandwidth. However, to start with I have made this test setup to ensure that RFSG performs similar to a Agilent / any other signal Generator. The results are pretty different from that of RFSG and the Agilent Signal Generator as depicted in the first post. 

Following are my further queries:

1.  Does RFSG takes a DC Voltage similar to that of linear ramp?

2. Can RFSG generate Linear Frequency Modulated (LFM) Pulse?

3. If not, any similar device which can generate LFM Pulse?