HP 8753E manual Measured Effective Directivity

A c t u a l

Directlvity

Tof L o a d (r,)

Measured

D i r e c t i v i t y

Before

Correctlo”

CD,)

‘\

‘--Efiechve Directlvity

A f t e r CorrectIon

(DA- D, = -I-,)

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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).

V 5,lA=11180'

s(-~)(ERF)

II,,,, = EDF+____

~-EsF(-~)

J

Figure 6-39. Short Circuit Termination

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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