question about Rf harvesting

[slashx15]

Pls enlighten me about this topic...

I keep on reading about rf harvesting from ambient environment sadly now all of it is jumbled up T_T

When they say environment, does that mean anywhere?

What frequency do they use? why 900Mhz and not use 2.4Ghz or viceversa..

What battery could you recommend for this system, i am planning to use a capacitor bank and try to charge a cellpone or laptop.

Which type of antenna would fit it best?

Do you have a circuit of a charging system, its kinda confusing tnx ^^

 

[dick_freebird]

It's all about the environment and the envelope. What RF
energy is expected to be present, and "how big a net" are
you allowed to fish with?

Expect that in most cases there will not be enough field
strength / power to do the kind of charging you imagine -
energy harvesting is for circuits that have very sparse "on"
periods and plenty of time to work on their tan.

 

[klystron]

Remember that the electromagnetic path loss is proportional to 1/(RxR) (R being the distance between the EM source and the receiver) The path loss is also proportional to 1/f (higher frequencies are more attenuated.) To maximize the engery : be as close as possible to source ; use as big as possible antenna ; use as low as possible a frequency (but you will need a suitable source at that frequency)