Wirekess capacitive power coup;ing

Well, for starters, a capacitor is not a "short". The displacement current in a given circuit (for a given capacitor) increases as frequency increases. Both capacitive and inductive coupling may be used, but the inductive mode is far superior; look at the equations and the constants involved.

Earth? Ground? What is that: Einstein said it is all relative (aunts,uncles, etc). For the not-so practical capacitive coupling case, the coupling to be considered (first rough approximation) is the capacitance between the devices. Then add in the losses == capacitance (coupling) to earth ground (or chassis ground).

Perhaps more digging into theory is needed.

Oh, BTW, i forgot to mention the capacitor/capacitance (in question) is BETWEEN those plates. The loss part is BETWEEN each plate and ground/chassis.

It isn't, really.

You would need to have a pair of plates on each device. You'd do best to drive the plates on the transmitting device differentially around some center voltage, and receive the same way.

For reasonably thick dielectric and reasonably small plates you'll need unreasonably large voltages -- for this reason alone I suspect that for most practical applications your best bet would be to dispense with capacitive coupling and use inductive coupling instead.

As Father Guido Sarducci has explained."Ground is everywhere."

You don't want current flowing everywhere; that's radio broadcasting and is simply bad manners from a user interface point of view, if it doesn't cook or kill.

You could localize the current flow by providing a superior local capacitive return, driven exactly out of phase. This could cancel external currents at lower frequencies.

RL

As has been pointed out, no, it isn't.

Not a guru, but here's my US$0.02 anyway.

Consider an ordinary air-gap capacitor with a large air gap, connected to a freestanding (ungrounded) AC power supply. The capacitor is thus the loa d for the power supply and it dissipates power per its reactance (somewhat oversimplified).

You have a device that you want to charge, and it requires current at the same frequency that you're feeding the capacitor. Take its input leads and attach metal plates to each one (on opposite sides of the device to be cha rged) and suspend it within the capacitor gap so that none of the plates to uch.

You now have two air-gap capacitors in series with the impedance of the d evice to be charged between them.

You don't need to establish any ground in that case.

Now consider the original large-air-gap capacitor to have one plate attac hed to something we'll call "ground", be it the actual physical Earth or so me metallic object to which one end of the power supply is also attached, w ith its other plate suspended above whatever you're using as a ground plane .

Now place one of the attached plates of the device to be charged on the g rounded plate, and you have the original capacitor in series with the imped ance of the device to be charged.

How close the plate is to ground, and the spacing between the plate and d evice will determine the voltage the device to be charged sees, so there wi ll need to be some converting done.

Now ground one end of the power supply and attach a metal terminal to the other end- it creates an AC field that "reaches out" to any grounded point ; the field's intensity obviously drops off with distance. You can then tak e your device to be charged anywhere such that one of its terminals is grou nded and the other is in the air so as to "catch" some of the created field , but distance will kill the charge rate.

This is essentially Tesla's original idea for wireless power transmission , except he believed it was due to longitudinal waves rather than Hertzian transverse waves.

He was wrong on this point, of course.

Mark L. Fergerson

A flux capacitor will do what you need!

Jamie

Oh I also forgot, along with that Flux capacitor, you also need a biocylic feedback reverberating diode.

Jamie