Re: NEC-LIST: antenna isolation and Maximum Coupling calculation

>This is how I did the calculation:
>I give antenna 1 a 1.0 V voltage source and no load. Antenna 2 has a
>load of 50 ohm (no voltage source). The current in the source
>segement of antenna 1 gives me Y11, the current in antenna 2 Y21.
>regards,
>
>Rogier van Aken.

Hello, Rogier. You're not determining the y (admittance) parameters
correctly. At a given frequency two closely-coupled antennas can be
treated as a two-port passive network. The admittance (y) parameters
are determined as follows:

  y11 = i1/v1 with v2 = 0 (antenna #2 feedpoint is short-circuited)

  y12 = i1/v2 with v1 = 0 (antenna #1 feedpoint is short-circuited)

  y21 = i2/v1 with v2 = 0

  y22 = i2/v2 with v1 = 0

Note that for this network y12 = y21. At no time should you be
terminating either antenna feedpoint with 50 ohms. Following a
determination of the y parameters, the maximum coupling may be
calculated as follows:

  Max Coupling = [1-Sqrt(1-L^2)]/L

where L = MAG(y12*y21)/[2*Real(y11)*Real(y22) - Real(y21*y21)]

Of course if you change frequency you will have to use NEC to obtain
a new set of y parameters. Hope this helps. Sincerely,

-- 
John Wood                               (202) 767-2608
Code 5550                               (202) 767-3377 (FAX)
U.S. Naval Research Laboratory          e-mail: wood_at_itd.nrl.navy.mil
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