Directivity

Directivity is one of the measurements available in the Manage Curves dialog box of a Graph Tab and represents the directivity value of a directional coupler. The equation is modified to create negative directivity values, which are more convenient when plotting with negative S-parameters. Directivity is a measure of the ability of a coupler to isolate forward and backward traveling waves. The equation used to calculate the directivity is:

Directivity = Sij – Smn  (dB).

Where,

i = The “To Port” you entered in the Isolation Ports section (this should be your isolated port)

j = The “From Port” you entered in the Isolation Ports section (this should be your input port)

m = The “To Port” you entered in the Coupling Ports section (this should be your coupled port)

n = The “From Port” you entered in the Coupling ports section (this should be your input port and the same as j)

Please see the Measurement Properties topic for an explanation of each field in this dialog box.