Re: NEC-LIST: Negative driving point impedances in phased arrays

I have observed this situation many times over many years when designing
phased array antennas. It results simply from not having the phases and/or
amplitudes of the near fields properly combining - proper in the sense of forcing the
element currents to achieve the values necessary for the formation of the
desired pattern. My experience does not suggest that it indicates any significant
underlying physics, which would certainly warrant trying to enhance the
"intuitive" physical analysis of the fields. I would say that it is simply a case
of having phases that are way to far off of target.

I have probably read every significant book on antenna theory published in
English, and I don't recall any discussions of this issue. That is because it is
not a case of anything highly significant, any more than simple resonances
are, and there is little to be learned by looking for any deep meaning. If
someone finds some new enlightenment, however, I would certainly like to hear about
it. But for now, I am satisfied knowing that power flow (in/out of array
elements) is what matters and there are really no phase angles that are golden
numbers at the basic physics level.

The Yagi array actually has negative mutuals, which nicely expresses the
power flow into the parasitic elements.

Eric von Valtier K8LV

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