Short Piezo VLF Antennas

Thread Starter

joeyd999

Joined Jun 6, 2011
4,291
I found this article interesting -- even though I don't understand it. Maybe someone can explain it to me?

https://www.electronicdesign.com/analog/piezo-based-approach-dramatically-shrinks-vlf-antennas

I think it is saying that the physical resonance is greatly amplifying the AC voltage applied to the antenna, therefore somehow improving efficiency. But is not one still limited to the low efficiency of a short dipole? And, the energy equation still has to balance, no?
 

nsaspook

Joined Aug 27, 2009
6,704
Ok...so you posted a similar article. But I still don't understand it.
Yes, it's a mainly near field device that uses the high Q resonator to increase the concentrated (the crystal converts the electrical signal into a acoustic wave that travels much slower than a EM wave inside the crystal making the resonator electrically longer) e-fields physical cross-section in space so a larger fraction of the reactive energy can be converted to radiative near field (Fresnel region) energy for far-field radiation. The phase shift across space is still small and the radiation resistance is very low. So while the efficiency is better, it's still poor when compared to a physical dipole.
 

Thread Starter

joeyd999

Joined Jun 6, 2011
4,291
Yes, it's a mainly near field device that uses the high Q resonator to increase the concentrated (the crystal converts the electrical signal into a acoustic wave that travels much slower than a EM wave inside the crystal making the resonator electrically longer) e-fields physical cross-section in space so a larger fraction of the reactive energy can be converted to radiative near field (Fresnel region) energy for far-field radiation. The phase shift across space is still small and the radiation resistance is very low. So while the efficiency is better, it's still poor when compared to a physical dipole.
So, essentially a (local) large alternating E field with a non-existent H field. Correct?
 

nsaspook

Joined Aug 27, 2009
6,704
So, essentially a (local) large alternating E field with a non-existent H field. Correct?
It has a very low H radiated field (hence low power) due to the spacial size limitations on the electrical length limiting the phase shift across the antenna even with the enhanced temporal effects of the Piezo resonator dielectric on antenna electrical size at the VLF range.

https://phys.org/news/2015-04-electromagnetism-enable-antennas-chip.html
The researchers determined that the reason for this phenomenon is due to symmetry breaking of the electric field associated with the electron acceleration. In physics, symmetry is an indication of a constant feature of a particular aspect in a given system. When electronic charges are not in motion, there is symmetry of the electric field.

Symmetry breaking can also apply in cases such as a pair of parallel wires in which electrons can be accelerated by applying an oscillating electric field. "In aerials, the symmetry of the electric field is broken 'explicitly' which leads to a pattern of electric field lines radiating out from a transmitter, such as a two wire system in which the parallel geometry is 'broken'," said Sinha.

The researchers found that by subjecting the piezoelectric thin films to an asymmetric excitation, the symmetry of the system is similarly broken, resulting in a corresponding symmetry breaking of the electric field, and the generation of electromagnetic radiation.
https://en.wikipedia.org/wiki/Dielectric_resonator_antenna

This is at microwave frequencies.
 
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