HP 8753E User Manual page 345

A c t u a l
D i r e c t i v i t y
A f t e r
Figure 6-38. Measured Effective Directivity
Next, a short circuit termination whose response is known to a very high degree is used to
establish another condition (see F'igure 6-39).
Figure 6-39. Short Circuit Termination
The open circuit gives the third independent condition. In order to accurately model the phase
variation with frequency due to fringing capacitance from the open connector, a specially
designed shielded open circuit is used for this step. (The open circuit capacitance is different
with each connector type.) Now the values for Enr , directivity, Esr , source match, and ERF,
reflection frequency response, are computed and stored (see Figure 6-40).
6-64 Application and Operation Concepts