EH antenna for real?
Would those of you with a theoretical background be able to comment on
the following. Looks interesting, but I have never seen the principle applied. http://www.eh-antenna.com/library/EH...DEFINITION.pdf Here is a quote from the article: "Next we see the EH antenna is created by shifting the phase of the applied current relative to the applied voltage. This causes H to be delayed an additional 90 degrees, and is now 180 degrees relative to the applied voltage. H has also been delayed 90 degrees and is now in phase with the applied voltage." Can the effect described be achieved in practical terms, and if so, what would be the simplest way to demonstrate it? IOW how is the phase shift described actually implemented in terms of basic hardware? Thank you for your reply. Klaus Jensen |
EH antenna for real?
"Klaus Jensen" wrote in message
... http://www.eh-antenna.com/library/EH...DEFINITION.pdf It's pretty bogus. His analysis is over-simplistic: Sure, if you look at the fields close to a Hertzian antenna, they're *nearly* (but not exactly) 90 degrees out of phase, and thus most of the energy present is just circulating around rather than radiating, but whatever energy *does* end up radiating is already present in that near field! It's just that the equations for the vector magnitudes of the E and H fields have different dependencies on R, so what you "see" changes as you move away from (or up and down) the dipole. An antenna with a given applied terminal voltage and radiation resistance radiates the identical power as any other antenna with the same voltage and radiation resistance -- the only thing you can change is the *pattern* of that radiation. Similarly, loss in an antenna comes about from the finite resistance of the materials constructing it. It's true that this can vary from one antenna to another, since you can modify the current distribution on the material and loss is I^2*R, but the paper cited only discusses terminal voltage and currents (and not current along the antenna itself), so the claim that it's inherently less lossy is quite dubious. I'm not suggesting that the "EH antenna" isn't useful, just that the theory presented is wrong. The deal here is that, in a certain sense, signals *like* to propagate, and it's surprising what you can string up and still get to work OK, even though what's *really* going on isn't what you think. See, e.g.: http://www.w8ji.com/e-h_antenna.htm -- or just Google around some. |
EH antenna for real?
Klaus Jensen wrote:
Would those of you with a theoretical background be able to comment on the following. Looks interesting, but I have never seen the principle applied. http://www.eh-antenna.com/library/EH...DEFINITION.pdf Here is a quote from the article: "Next we see the EH antenna is created by shifting the phase of the applied current relative to the applied voltage. This causes H to be delayed an additional 90 degrees, and is now 180 degrees relative to the applied voltage. H has also been delayed 90 degrees and is now in phase with the applied voltage." Can the effect described be achieved in practical terms, and if so, what would be the simplest way to demonstrate it? IOW how is the phase shift described actually implemented in terms of basic hardware? Thank you for your reply. Klaus Jensen Klaus, I make antenas all the time. my site is www.fwt.niat.net these are not EH antennas but an innovative form of dielctricl embedded antennas with dielctric shaped wave front forming. This antenna use a phase shifted (90 degree) signal to drive the H field singal when compared to the E fieled driving point. This creates an antenna that can be consider a two element phased array. if you have an antenna elemnt, and you add a second element and control its electrical phase as well as it physical spatial phase, when you observe the effectvie radiated signal you can get higher gain, or lower sidelobs by adjusting the phase. Clearly this unit will be of narrow bandwidth as a constant 90 phase over a wide frequency band is typically band limited. a constan length of feedline has a phase that increase proportionate with frequency... Best Regards, marc |
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