NEC-LIST: RE: NEC-LIST:Simulations of Q and the Chiu-Harrington Limit

Hi Chip,

I'm assuming that you are considering antenna designs that are
self-resonant (series resonance - dX/dw is positive) at or below some
small KA (KA < 0.5). If so, you should be able to design an antenna
with a lossless Q that is at least within 1.5 times the fundamental
limit. Small antennas with Qs at these levels have been described in
the literature.

The only place to be cautious is at frequencies near an anti-resonance
(parallel resonance - dX/dw is negative). Near an anti-resonance, the Q
of the antenna may approach zero. For this reason, Q cannot be
approximated from 1/BW (BW being the 1/2 power or conductance bandwidth)
or from the reactance formula: Q = (w/2R) (dX/dw + |X|/w).
Additionally, in the anti-resonance regions, you should cautious as to
how you interpret the relationship between Q and the fundamental limit.

Steve Best

> -----Original Message-----
> From: nec-list-admin_at_gweep.ca
> [mailto:nec-list-admin_at_gweep.ca] On Behalf Of Fractenna_at_aol.com
> Sent: Wednesday, November 27, 2002 7:56 AM
> To: nec-list_at_gweep.ca
> Subject: NEC-LIST:Simulations of Q and the Chiu-Harrington Limit
>
>
> Hello All,
>
> I am doing a literature search on electrically small
> antennas, as preparation
> for publication. Right now, I am trying to see the best that
> has been done in
> finding low Q antennas at small values of KR.
>
> I am aware of Altshuler's Mar 2002 paper in Transactions, as
> well as other
> sources including the APS 2002 presentation of Gionvatorrio
> and Rahmat-Samii.
> As we have new data that will prove of interest, it is
> important that we do
> our best to report all that has been known on low Q antennas
> at small values
> of KR, so that issues may be definitely addressed and
> answered. In other
> words, what are the best known designs that approach the
> Chiu-Harrington
> limit?
>
> If you are aware of simulations that beat Ed Altshuler's 5
> wire or a (self
> similar) conic section, I would appreciate a citation or
> information before
> publication (which will, of course be properly attributed).
>
> Many thanks!
>
> Chip N1IR
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