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Voltage induced on a metal plate in free space??

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boltzmann69

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Hi All,

Looking for some ideas or techniques as I would like to measure the voltage induced on a square metal plate in free space. Its not so much about the measuring equipment but more how I can couple to the plate. I considered cutting a slot in the plate and basically turning the thing into a slot antenna and measuring across the feed point. But I guess if the plate is large with respects to wavelength then the whole thing needs to be covered in lambda/2 slots spaced accordingly, and then all the voltages summed. Then of course this becomes polarisation and frequency dependent.
I'm guessing some form of transformer or loop coupling to the plate is the way to go but I'm not sure how this might be achieved?

Any ideas/input would be great.

Thanks,

Stu.
 

E Kafeman

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Induced voltage is depending on plate orientation and size relative to signal source placement and wavelength. Peak voltage will be highest if measurement point relative to reference point is lambda/2 + x wavelengths multiples apart. A simple meter of this voltage is a diode peak detector.
 

boltzmann69

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Induced voltage is depending on plate orientation and size relative to signal source placement and wavelength. Peak voltage will be highest if measurement point relative to reference point is lambda/2 + x wavelengths multiples apart. A simple meter of this voltage is a diode peak detector.
Hi and thanks for the response.

I understand what you're saying and I know that I can simply rectify the voltage induced upon the plate but my main query is how would you couple any such meter/circuitry to the plate. Now I'm thinking some form of transformer coupling might be an option? Just can't quite see how I would implement this yet.
 

E Kafeman

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Resulting measurement is a DC voltage. Assume your detector is placed in one end of the plate and probing the other end. Depending on frequency can different solution be possible to transfer measured voltage to somewhere else without affecting "free space". For low frequencies can probably a LP filter be enough. A bit more complicated is to modulate a LED, which can be read from distance or over fiber.
 

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