I am trying to do a one port VNA calibration for measuring filters at the GHz band. The VNA that I am using is Keysight E5063A. However, I am running into some conceptual as well as some practical problems. Any help will be greatly appreciated.
I do not have the calibration kit provided by Keysight. However, I am using a standard open, short, and load (50 Ohm) that I found in the lab I work in.
Open is the standard BNC Open. Short is the standard SMA short. Load is 50 Ohm mini circuits, operating range DC - 18 GHz, Model number: 30918. The band at which I am calibrating is 4 GHz to 6GHz.
I connect a standard ST18 SMA, 36 Inch cable to port 1 of the network analyzer. The purpose of this is to reduce mating cycles. Going into the calibration menu, select one port calibration. I connect BNC Open, and press open calibrate. I connect Short, and press short calibrate. I connect load, and press load calibrate, click done, and I save this calibration.
However, now when I see the results on the smith chart on the network analyzer, I do not see a dot on the edge of the smith chart for short and open. Instead, I see an arc. For the load, I see a dot. I do see open and shorts maintaining a 180 degrees phase separation throughout the 4 GHz to 6 GHz band.
Why is the arc caused in the first place? Is it because of fringing capacitance (inductance) for open (short)?
Can I go ahead and make measurements of filters with this calibration?
I am worried that because of this, the complicated circuit network that I am trying to measure, may not reflect its right characteristics due to calibration errors, if there are any. In such a circumstance, what can I do, to know for sure that what I am measuring is exactly what it is at this band (and there are minimal systematic errors.)