Parasitic elements close to driven element.

[dbvanhorn]

I'm familiar with using parasitic elements out away from the driven element as directors or reflectors.

I have seen an antenna that used a parasitic element close in to the driven element. For example if the DE were 1/8" wire then the PE would also be 1/8" wire spaced maybe 1/8" away.
The DE induces current flow in the PE, but does this actually improve radiation, or just double the loss?

 

[VEBill]

There are some types of matching systems that may appear a bit similar (ot really) to a much shorter element. But they're typically connected to the DE near the open end. You may already know this.

Ref: Google Images of Gamma Match

Can you find on-line (or post) an image?

 

[dbvanhorn]

Familiar with those, this is a free floating element that is not connected to the DE but may be identical to it, just very very close, so that it does not act as a reflector or director at this frequency.

 

[VEBill]

Perhaps effectively it just thickens up the driven element making it wider bandwidth. This one actually makes a wee bit of sense. Use the same element wire to save costs; just use another.

Is the 2nd DE the same length as the primary DE? Multiband Yagi antennas can have shorter elements interspersed between the 'normal' elements. Some of them can end up arbitrarily close to the other elements.

I just did a quick search of Google Images using the keywords 'antenna parallel driven element patent' to see if any inventions match your description appeared. Nothing obvious in the first bunch.

Is it a serious antenna? Some of the crazy antenna-like things sold to consumers (e.g. TV) defy any logical explanation.

 

[dbvanhorn]

I have seen other designs that seem related, like the floating sleeve dipole.

It's a serious design, I am working with it at 2.4G in Sonnet. I have the main antenna on top of the PCB, and of course the area on the other side of the PCB is "free".
So, I wondered if there's something useful to be gained here, either by using the change in dielectric to tune the main antenna, or in adding additional radiation. I'm not convinced that it does have a benefit in the far field though since the exciting current had to come from the main antenna, and I know the additional element has some finite loss.

Just playing with ideas at this point.