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Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
Many hand calculations and simulations for antennas ignore the resistivity of the metal at least for initial designs because it is frequently negligible. You could think of the antenna as a two-port connected to free space on its output - the unloaded antenna may have an infinite Q but when you connect it to free space you end up with a loaded Q because energy will be flowing into space as the antenna resonates. The fundamental definition of Q is the ratio of stored energy to energy lost per cycle. If you "disconnected" the antenna from free space by putting it into a resonant cavity you would end up with some sort of cavity resonator, and you would indeed have an enormous Q if you were using superconductors.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Mattski wrote ...
Many hand calculations and simulations for antennas ignore the resistivity of the metal at least for initial designs because it is frequently negligible. You could think of the antenna as a two-port connected to free space on its output - the unloaded antenna may have an infinite Q but when you connect it to free space you end up with a loaded Q because energy will be flowing into space as the antenna resonates. The fundamental definition of Q is the ratio of stored energy to energy lost per cycle. If you "disconnected" the antenna from free space by putting it into a resonant cavity you would end up with some sort of cavity resonator, and you would indeed have an enormous Q if you were using superconductors.
Hm... better think of a different thing to work on in the future then... I was planning on trying to make induction efficient... I guess I'll study lightning then :P
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Yeah, sorry for confusing everyone. As it happens, superconducting resonator cavities could be used for novel applications, however the inverse square law still applies even to a laser. This is why laser beams aren't used for wirelessly sending power, the beam spreads out far too much over any sensible distance.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
Conundrum wrote ...
Yeah, sorry for confusing everyone. As it happens, superconducting resonator cavities could be used for novel applications, however the inverse square law still applies even to a laser. This is why laser beams aren't used for wirelessly sending power, the beam spreads out far too much over any sensible distance.
-A
Lasers do spread out but it's better than microwaves. I think a bigger problem is the low efficiency of generating optical laser power and turning it back into electricity. Microwave power can be generated at high efficiency with magnetrons or similar devices, and a well-designed rectenna array can turn it back into electricity at >70% efficiency.
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Wireless power breakthrough?
