RF VNA

[Titanium]

How to implement a LAbVIEW TRL calibration of RF VNA? 

[A_Donfigulation_Error_Has]

Hi Titanium,

An example of this can be found in the Example Finder for the NI PXIe-5632 VNA. Go to LabVIEW and navigate to Help >> Find Examples. Then click on the Browse tab and navigate to Hardware Input and Output >> Modular Instruments >> NI-VNA >> niVNA_TRL_CALvi. 

Regards,

Jason L.

[Titanium]

ok, thanks.

in the VI, What does the number of points means? Also the IF bandwidth??

What reference plane is the typical? end or middle of Standard1? any difference??

What is "band break point type"? Manual breakPoint Frequency?

why there is 2 bands?

lastly, can we access the TRL Cal settings, or see the equations or computations behind the DLL that computes the result...

[Titanium]

Does NI provide TRL Calibration Standard Kit or need to outsource to other suppliers??

[A_Donfigulation_Error_Has]

Hi Titanium

The number of points refers to the number of points to sweep through for the Calibration/VNA. Typically you can provide a Min/Max sweep frequencies such that the number of points will determine the frequency step sizes that the VNA will use.

IF Bandwidth - Please go to the NI Vector Network Analyzers Help file that can be found on the Start Menu of your computer. Navigate to NI Vector Network Analyzers Help >> Devices >> NI PXIe-5632 >> NI 5632 Block Diagram and Theory of Operation for more information. In general, increasing the IF bandwidth improves the speed of the sweep measurement, but it introduces more noise. Decreasing the IF bandwidth yields more accurate measurements but at a lower speed. Valid values for the 5632 are the following: 10 Hz, 30 Hz, 50 Hz, 70 Hz, 100 Hz, 300 Hz, 500 Hz, 700 Hz, 1 kHz, 3 kHz, 5 kHz, 7 kHz, 10 kHz, or 30 kHz, 50 kHz, 70 kHz, 100 kHz, 300 kHz, or 500 kHz.

The band breakpoint is the frequency at which the TRL calibration stops using the standards associated with one frequency band and begins using the standards associated with the next band. By setting manual, you can specify this frequency, otherwise the driver will try to determine it on its own.

You cannot access the TRL Cal settings or see the equations or computations behind the DLL that computes the result. The DLL's are not open to the user.

There is no NI TRL Calibration Standard Kit.

Regards,

Jason L

[Andy_Hinde]

Hello Titanium,

Jason L. has done a great job responding to your questions. Let me try to elaborate a bit on a couple of them.

The reference plane is the physical location where the calibration of the system 'ends' and the measurement 'begins'. If you think of a VNA with cables, you attach cal standards to the cable(s) (in a traditional SOLT cal) and you are establishing the calibration reference plane at the ends of the cables. This means everything 'behind' the cables is calibrated out, and everything between the cables is what is being measured. 

The reference plane is just a term used to describe where the calibration physically occurs. A standard reference plane for SOLT cal is the end of the VNA cables. A standard reference plane for a TRL cal is the junction where the VNA cables/connections meet with the Through/Reflect/Line (TRL) standards, usually the junctions of the PCB.

Regards,

Andy Hinde

Senior Systems Engineer

RF and Communications

National Instruments

[Titanium]

Thanks Jason and Andy for the clear explanations.

However, why there is still need to choose 1 or 2 Bands?

What I know is that during calibration, the smaller the bandwidth, the more precise the calibration compared with doing it on a large bandwidth.

Ex: band1: DC-3GHz band2: 3GHz-8GHz is better compared to calibrating one shot from DC-8GHz, is that correct?

In the Front Panel of the VI, there is the length for each standard, what is the length, where to get the value? is it the wavelength of your frequency of operation? or 1/4 of your wavelength?

Can we choose any length for the transmission lines? wavelength depends on Center Freq, so different pairs for each frequency or the cal standard kit is applicable for any freq bandwidth?

What characteristic to follow for TRL standard?

Thru - any length of tx line

Reflect - either Open or Short

Line - longer by 1/4 wavelength than the Thru

Lastly, the line loss value & frequency? How to compute? is it the specification of the material used in doing the Tx Line?

[Andy_Hinde]

Hi Titanium,

It appears you are looking for some tutorial information on TRL calibration in general. I recommend you read this white paper as it should answer most all of your questions:

http://www.anritsu.com/en-US/Downloads/Application-Notes/Application-Note/DWL3555.aspx

Thanks,

Andy

[ASEAN]

Thanks for all the answers, it really helps.

Since NI don't have TRL Calibration kit, can we just use the SOLT standards? Will the results be the same or expect to be less accurate as using transmission lines?

Since it is TRL (Thru, Reflect, Line), Thru is available and the Reflect (Short or Open), what can you recommend for the other Line?

Or how about changing it to TRM (Thru, Reflect, Match) since the counter-part standards are available.

Also, any idea on what are the differences between TRL and TRM? When and where is it good to use for calibration?

Lastly, are there plans for NI to provide TRL kit in the future?

[A_Donfigulation_Error_Has]

Hi,

This whitepaper discusses the disadvantages and advantages of using SOLT calibration vs. the other calibration types: http://www.ni.com/white-paper/14114/

Regards,

Jason L.