touchstone insertion loss calculation in excel
zhonghua_li said:
1.get the complex impedance of ZL,by the equation of S11 = (ZL - Z0)/(ZL + Z0);
2. calculate the S11 with other Z0 (eg. 100ohm) by the equation of S11 = (ZL - Z0)/(ZL + Z0) too.
it's easy to be calculated by matlab's complex operation
In 1-port measurement, you can do that. However, with 2-port measurement, the measured S11 in 50Ohm system is affected by the load on port2.
For a certain network, a unique Z, Y, or T matrix can be used to fully describe the network. While the Zo needs to be defined for the S matrix, which means S matrix can be different with different Zo. Usually, the S parameters measured by a VNA are normalized to 50Ohm. Several ways to renormalize the data to 100Ohm.
1. Use CAD tools. ADS, Ansoft Designer, Microwave Office, and EldoRF are all able to do the renormalization easily. In ADS, the S2P component can have CITI file as input. Let me know what software is available for you, I can show you how to do this.
2. Mathematic tool (matlab, or even in Excel). Transfer the S parameter matrix to either Z, Y, or T matrix. Then transfer them back to S matrix in reference to the new Z0. You may need a reference book on microwave network for the equations, eg Pozar's Microwave Engineering.
Regards,
hititman