Specifications

Both three port completion steps will start with a two port calibration

(first 12 terms) and will use the same isolation measurement steps to

get the last 4 terms. The two methods differ in how they find the

middle 8 terms in the above list

As one might expect, the SOLT version first proceeds by performing a

one port cal on port 3 by measuring an open, a short and a load. These

measurements allow the computation of source match, directivity and

reflection tracking terms. The remaining thru line measurement(s)

allows the computation of load match and the required transmission

tracking terms to complete the model.

The TRX method follows in the path of the LRL/LRM/TRM methods

and exploits some of the data redundancy in the standard SOLT

approach. The thru line measurement allows the direct computation of

directivity, load match and some of the transmission tracking terms.

The short measurement allows direct computation of the source match

and the completion of calculation of the remaining tracking terms.

Since the 24-term model is shared between the two methods, the

calibration will be applied in the same way for both via a matrix

equation system. Figure 7-7 illustrates the three port error model. An

error box is associated with each port that contains the coefficients

describing that port’s non-idealities.

MEASUREMENT 3-PORT TRANSMISSION

CALIBRATION AND REFLECTION CALIBRATION

MS462XX OM 7-25

perfect VNA

physical port 1

physical port 2

physical port 3

ax,bx

ay,by

az,bz

a1,b1

a2,b2

a3,b3

Figure 7-7. Three-Port Error Model