[time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer

[Chuck Harris]

Hi David,

Since I apparently have no cred, I can give you a quote from Jasik:

"A right hand helical antenna transmits or receives right-hand
polarization while a left-hand helical antenna will transmit or
receive left-hand polarization."  Jasik, "Antenna Engineering Handbook",
First Edition, p17-3.

Which seem fairly clear to me.

In my experience, there really is no confusion about that among
*competent* antenna engineers... among those less schooled in the
subject, any amount of confusion is not only possible, but probable.

I could see how one could be confused about the definition, as it is
purely a matter of convention.  That RHCP is defined as the wave
propagating in the clockwise direction as viewed from the source could
just as easily have been defined as being viewed looking towards the
source... but, since the current convention was defined by the IRE
more than half a century ago.  It shouldn't be all that controversial
anymore.

-Chuck Harris



Dr. David Kirkby wrote:
> On 06/ 5/12 04:06 PM, Rex wrote:
>> I took a scan through Kraus "Antennas" since he did much of the
>> definitive work on Helical antennas. In his chapter on Wave Polarization
>> he gives a mathematical definition of Left- and Right-circular
>> polarization, then quickly mentions that the IEEE definition is the
>> opposite. He has a footnote: "This IEEE definition is opposite to the
>> classical optics definition."
>
> That's basically what Wikipedia says about the optics. They don't reference it, so if
> it is referenced in Krauss, that would be a worthwhile reference.
>
> Most antenna people seem to accept the standard definitions as being "IEEE Standard
> Definitions for Terms of Antennas IEEE Std 145-1983"
>
>> So it seems our current antenna engineering uses the IEEE definition for
>> RHCP and LHCP, but earlier work on EM wave theory had defined
>> right-circular and left-circular exactly reversed from IEEE. So, combine
>> that with the reflection flipping and it is not hard to think why there
>> might be confusion.
>
> I'm not saying Chuck is wrong about one needing the same sense at each end, but I
> would disagree with him when he says "I guarantee you it doesn't cause any
> controversy among those that use circularly polarized antennas." There certainly is a
> lot of confusion over this topic, even among people who design them. I don't think
> the confusion is related to reflections (everyone seems to know that) and I don't
> think it's related to different conventions either.
>
>
> I was going to try to simulate this by putting two helix antennas and coupling them.
> But setting that up is a lot more difficult for me than just building three antennas.
>
>> I looked all around for a simple definition of the RH, LH quality of the
>> wave from a helix antenna. I assume I might have extracted it from pages
>> of formulas and theoretical explanations, but why not just clearly state
>> it in a book that is largely about helical antennas. Somewhere else (in
>> Kraus) I read that the IEEE definition of a RHCP or LHCP wave from or to
>> a helical antenna had the same handedness as the helix of the antenna.
>
> Quality of polarization is a very complex topic. See the paper:
>
> "The definition of cross polarization"
> Antennas and Propagation, IEEE Transactions on
> Date of Publication: Jan 1973
> Author(s): Ludwig, A.
> California Institute of Technology, Pasadena, CA, USA
> Volume: 21 , Issue: 1
> Page(s): 116 - 119
>
> I've reprinted the abstract below for completeness, though you can read it on the
> IEEE site without paying.
>
> ---------------
> Abstract
>
> There are at least three different definitions of cross polarization used in the
> literature. The alternative definitions are discussed with respect to several
> applications, and the definition which corresponds to one standard measurement
> practice is proposed as the best choice.
> ---------------
>
> I printed off a copy of that paper with the intension of trying to understand it. I
> think the maths gets a bit heavy for me, but the more difficult problem is I was
> unable to read the small symbols on A4 paper. So it looks as though I'll have to read
> it on a computer and hope the quality is good enough.
>
>> Unfortunately in that writing he did not bother to explicitly mention
>> what he meant by the handedness of a helix. I assume he meant it to be
>> the same as the handedness of a screw, but he didn't say that, so once
>> again, a missed opportunity.
>>
>> I'm not arguing with you, Chuck, just pointing out why there might be
>> room for confusion in some circles. (Pun intended.)
>
> One method of logically arguing for both antennas to be the same is reciprocity
> theorem. So I think Chuck is right on the engineering facts, but is wrong about the
> level of confusion it causes. I wish I could find the post on the EDA forum, as there
> were many people making arguments for both cases.
>
> Dave
>
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