I just recently purchased an SMA cal kit where the manufactured provided s1p files of the open, short and load standards, but only gave an offset delay and offset loss for the female-to-female and male-to-male thru standards. I'm looking to write an algorithm to do data-based error correction. Finding the one-port error terms is straightforward, but I don't understand how to find the two-port error terms for a defined thru. I consulted Joel Dunsmore's book and he talks about the case involving defined thrus in Section 188.8.131.52 but doesn't provide much detail about the actual process. Any ideas how to proceed?