I am using an ENA E5071c vector network analyzer for two port microwave measurements. I am trying a TRL (Thru-Reflect-Line) calibration for the first time using four standards: Thru, Reflect and two Lines. I always perform thru, then reflect, then the lines (low frequency and then higher frequency defined). After I complete the calibration, I have no idea what to look for in terms of the S-parameters to verify the calibration was sufficient. Right now I end on a line, but I do not know what the line should look like on the smith chart (still learning all of this). Please enlighten me!

Thanks!

The line should look like the true response of the line, meaning it should have a slope that follows the curve Loss=Af^b where A and b are constants. For a coaxial airline, the value of b is 0.5. For microstrip on PCB it is more like .8 . You should normally see a smooth loss function. If you see ripple, you calibration is not so good.