Hello all,

I need to perform a TRL calibration on a Coplanar Waveguide. The CPW is tapered to increase the impedance. The gap (see figure) is where the DUT will be put.

My question is regarding the characteristic impedance that we need to provide at the time of the TRL calibration. Since the test fixture (CPW + tapered CPW) is non uniform and thus have a varying Zc, how do I find or define the characteristic impedance of each port?

A second issue that is boggling me is concerning the definition of the characteristic impedance. My design is leading to 3 different values for the impedances (Zpv Zvi and Zpv). My concern is which of these definitions is the most appropriate to use with the VNA measurements ?

Thanks in advance!

mil

I need to perform a TRL calibration on a Coplanar Waveguide. The CPW is tapered to increase the impedance. The gap (see figure) is where the DUT will be put.

My question is regarding the characteristic impedance that we need to provide at the time of the TRL calibration. Since the test fixture (CPW + tapered CPW) is non uniform and thus have a varying Zc, how do I find or define the characteristic impedance of each port?

A second issue that is boggling me is concerning the definition of the characteristic impedance. My design is leading to 3 different values for the impedances (Zpv Zvi and Zpv). My concern is which of these definitions is the most appropriate to use with the VNA measurements ?

Thanks in advance!

mil

What is the desired reference impedance for your measurements?

What structures will you use for cal (Thru, Line, reflect? Will the thru and the line be in the hi-Z case?).

In general, you do not need to know your impedance value, you only need to ensure that the Thru and the Line have the same value. If you want S-parameters (reflection relative to your ref impedance) that's it. If you want impedance, then the value of your thru and line z0 will set the center of the chart.