Re: NEC-LIST: Definition of Gain

At 09.37 02/03/00 -0500, George Hagn wrote:
>So here are several questions:

Personal comments:

>1) Do you believe that the definition of gain (of an antenna), when
>used with no qualifying adjective, should include mismatch loss or be
>defined in terms of a complex conjugate matched antenna?
>
>2) Do you believe that polarization mismatch in a link budget context
>should be part of the definition of gain or treated separately?

No to both. I think that antenna gain is a part of a link budget, as
polarization mismatch, or free space attenuations are. But is the
"antenna" gain.

On the other side, I ask myself whether another, different, definition
should be useful, i.e., a definition related to the antenna behaviour
with repect to its "nominal" specifications. I've seen somewhere a
distinction between

i) directivity
ii) gain (directivity times efficiency due to losses)
iii) realized gain (gain times the efficiency due to the return loss)
and definition iii) can take into account the nominal specification of
the antenna if the feeding line impedance (or the source impedance)
must be equal to the nominal input impedance of the antenna.

In the same way it is possible to include the polarization mismatch
respect to the nominal antenna polarization, using definition iii)
(and maybe with a more descriptive name) extended to include also the
polarization mismatch loss. In any case, I think that all these
definition must be linked only to the antenna, and not to its use.

>3) Do you believe that the definition of gain for a receive antenna
>should be the same as for a transmit antenna?

Absolutely yes. The essence of reciprocity for antennas is that an
antenna behaves in the same way whether transmits or
receives. Therefore I see no reasons to assign different meanings to
the same word, defining an antenna property, depending on how the
antenna is used. (Actually an antenna can be used at the same time as
Tx and Rx; it would be quite funny that such antenna has, at the very
same moment, two different values of gain)

Thanks for this possibility of express my view.

Yours sincerely

Giuseppe Mazzarella

-*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*-
Prof. Giuseppe MAZZARELLA Senior Member, IEEE

Dip. Ing. Elettrica Elettronica Univ. di Cagliari
Piazza d'Armi
09123 CAGLIARI ITALY

Ph. + 39 - 070 675 5884 Fax + 39 - 070 675 5900

E-mail Mazzarella_at_diee.unica.it
Received on Tue Mar 07 2000 - 04:27:51 EST