N5224 PNA VNA Automation using Labviw via GPIB | S21 extraction

[AbdulJabbar15]

Hi
I am trying to get S21 parameter across different angular positions of a rotator (having antenna attached)
from N5224A PNA (VNA) using Labview.
Although I am able to get S21 and saving it continuously in a text file in Labview. However, the problem is that there are certain readings after 3 to 4 correct readings, where received s21 gives a glitch, e.g., -200 power level (which is meaningless).

For example, power level -42 dB, -42.15, -38, and then -200, -200,-200, then again correct readings in the range. 

I guess there is some issue in the code or subVI which is causing these glitches.

If someone could please share a Labview code for getting S21 from Keysigth N5224A VNA.

Note that i am connecting a motor(rotator) for moving antenna, and measuring the radiation pattern using S21 from VNA.

See the attached text file with obtained S21 from VNA , as an example.

The Labiewcode file is also attached.

Any help in this regard would be highly appreciated. THANKS

[cstorey]

Ok, there's a few contradictions between your goal and your code:

1) the code configures a 201 point frequency sweep (s21 vs freq) but you mention extracting s21 at a specific power?  Which is it s21 vs freq or s21 vs power?

2) why are you averaging the data? (and calling it s22)

3) You are trying to make automated measurement, but triggering is manual. it should be IMM, you also want to wire the trigger to Channel 1.   You do want to have the program trigger a new measurement everytime you change the motor position, right?  

As for the code, you shouldn't be initiating/closing communication and configuring the instrument inside the loop.  Those operations are slow, and don't need to be done every iteration.  See attached.

Craig

[AbdulJabbar15]

Hi Caraig, Thanks a lot for reply.

Fortunately, glitches have removed recently, and code is working fine now. The issue was sweep type, it has to be linear. Earlier I was using Logarithmic which caused those glitches.
Else, S22 is just written there but I am getting S21 actually, using two ports. For automation, another Labview file runs parallel which actually controls the motor and scan angle. So for a fixed frequency, I am able to get full scan angular power pattern between transmit and receive antennas.

A beautiful plot you can see as attached, for instance.

 

[cstorey]

Glad its working.

The sweep must match your calibration (type and # of points) because if you are trying to do a measurement where you haven't caibrated it won't give you a valid result.

You should probably merge the two programs to control the motor and make s-param measurements. 😉

Cheers,

Craig