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From: Oleg Sollogub, RZ4HL
Date: 16 Jun 1999
Time: 14:54:13
Remote Name: 195.128.145.174
Hi, Ken,
There are some US patents (and other countries' patents) related to contra-wound antennas. See US Patents 4622558, 5442369, 56654723, 5734353...
You may have seen a reference to the West Virginia University's patent in a document dated June 19, 1996 and found at www.iascom.com/press/... It might be either US patent 5442369 (dated 1995) or 4622558 (dated 1986) which is mentioned in the document.
It cannot be considered a pure CFA, at least not as we use to think of it. But this depends on definitions. And I believe these kinds of antennas should work. The idea behind this, as I see it, is that E field can be created by a loop of "magnetic current". It means that instead of creating a tower to excite E field we can create a horizontal (i.e. low) toroidal structure which creates E field indirectly, through H field (somehow opposite to Mr.Hately's "antenneX"-published CFA where H field is created by E field). Depending on dimentions of toroidal structure, operating frequency, windings number and spacing and feeding, etc., antennas of this type may produce E and H fields in various spatial and phase and magnitude relations (and pure E field too), resulting in various polarizations and radiation patterns. And some specific configuratons may work more or less like CFA. It is not just my guess; "the cross-field properties of the toroidal embodiment of the invention" are also mentioned in patent 4622558 (see column 10 line 53).
Of course, any antenna is CFA. Without crossed fields, no radiation can occur. But let us call a CFA
an antenna, which radiates most of its radiated energy through crossed E and H fields found in a close proximity to it, rather than in a far-field zone (as it is understood traditionally).
Now we only need to formally define "most of radiated energy" (in percentage) and "proximity" (in terms of wavelength).
How do you like this definition? I think it is better than requiring special separate elements for E and H fields, because sometimes it may be difficult to separate one part of a conductive structure (wire, for example) from another, and to tell which part is for which field. For example, contra-wound helical toroids may produce rotating field, and the same part of antenna may excite E field at one moment and H field at the next moment. In other words, H field and E field excitation spots may move or rotate along antenna structure.
I will appreciate any further comments on the issue.
Best regards, Oleg