PicoVNA 106: Wrong response below 900kHz using SDK (Visual Studio)

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Daniel-dk
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PicoVNA 106: Wrong response below 900kHz using SDK (Visual Studio)

Post by Daniel-dk » Fri Jan 10, 2020 2:51 pm

Hi

In my application, a want to do a frequency sweep from 850kHz to 1150kHz and analyse this data using an application developed in Visual Studio.

Everything seems OK, but the sweep data captured using the GetData() function is not correct below 900 kHz. It seems that the 900 kHz is a "changeover" point of some sort - and it is independent of the sweep range and calibration.

The same sweep is fine when using the PicoVNA2 software.

See the attached pictures of the response in PicoVNA2 and that using GetData() in the visual studio application.
Capture1.PNG
Reponse in PicoVNA2
Capture2.PNG
Response using SDK
The basic functions used in the visual studio application is:

var cal = PicoVNA.SelectCal("..\\..\\..\\picoVNA\\Calibration_850kHz_1150kHz.cal");
var measure = PicoVNA.Measure("ALL");
var getData = PicoVNA.GetData("S11", "real", 0);

It is clear directly from the getData string, that there's a clear shift in the data at 900kHz.

What am I missing? How can I correct this?

best regards, Daniel

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