Re: NEC-LIST: Re: resonance and Q of an antenna and scattering system

If using a CAD package is the solution to computing stored energy, then it
would be interesting to know what approach the people that design/build CAD
packages use to compute the stored energy. Any ideas?

Malcolm M Bibby

----- Original Message -----
From: <wadavis_at_vt.edu>
To: <nec-list_at_gweep.ca>
Sent: Thursday, January 02, 2003 12:04 AM
Subject: Re: NEC-LIST: Re: resonance and Q of an antenna and scattering
system

> There is not a simple way to compute the stored energy needed for this
> computation. It has been the subject of work for several years and led
> about a half-century ago to the "fundamental limits" of antennas. The
> limits computed are based on lower bounds of the stored energy and thus
> give a lower bound on the Q. To get a smaller Q, you have to add loss,
> that of course cuts into the efficiency and results in a false measure of
> performance.
>
> At resonance, the stored energy acts much like a tuned circuit where the
> energy simply varies between the field components in time and maintains
> the stored energy as constant. About the only way to get at the Q for a
> specific situation is to compute the energy in a CAD package or to
> estimate it by a measure of the impedance bandwidth.
>
> Bill Davis
>
> > Happy new year, everyone.
> >
> > A dicussion of the definition of Q for an antenna is helpful to us.
The
> > conpect of the ratio of energy stored to the energy dissipated per cycle
is
> > according to the definition of the circuit theory. John B. Wood pointed
out
> > that in the case of an antenna, the energy "dissipated" consists of
that
> > dissipated as heat in the antenna structure and radiated into the
medium, and
> > the stored energy is that contained in the reactive near field of the
antenna.
> > The other important problems are what is the definition of resonance of
an
> > antenna or an antenna array, and how to determine the stored energy
contained
> > in the reactive near field of the antennas. Thank you for you kind
attention.
> >
> > Sincerely
> >
> > Long Li
> --
> The NEC-List mailing list <nec-list_at_gweep.ca>
> http://www.gweep.ca/mailman/listinfo.cgi/nec-list

-- 
The NEC-List mailing list <nec-list_at_gweep.ca>
http://www.gweep.ca/mailman/listinfo.cgi/nec-list