# how to design wireless power transmitter?

i need to design a wireless power transmitter and receiver, so that atleast 3 watt (at 5 volt) power is received at receiver section. transmitter and receiver can be at maximum distance of 2 to 4 meters. the transmitting and receiving antenna cant be more than 1 meter. My idea is to generate a high frequency wave, and amplify it using mosfets connected in cascode *connection. then improve the power by *darlington power transistors and transmit it using an antenna . rectify it in receiver by using schotky diodes.

please help me to choose — 1. appropriate operating frequency (please dont suggest microwave) 2. appropriate mosfets, and darlington transistors 3. appropriate antenna design (may be directive or non directive) 4. passive filter in receiver end

can i increase the power strength of signal, simply by using high power amplifiers? and coupling it to antenna by using transformer?

i know that radiated power is proportional to square of antenna current, which is again a function of radiation resistance. entire things goes more and more complicated in this way.

please help me to design such a transmitter( efficiency ca be anything).
###### Asked By: Sthitapragyan Pattanayak
1 year ago

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• Why do you need 3W to traverse 2 to 4 meters? Depending on frequency and terrain, 3W can travel quite a distance, especially if the transmitter [TX] and receiver [RX] can be in fixed locations — if you have line-of-sight between TX and RX, then with a focused antenna system you can reach quite a distance with 3W. But then, I’m assuming you want to use this for communication or data transfer. So…
• What is the actual purpose or application?
• Not sure in what country you want to run this device, but you probably should check local ordinances for radiated power.
• Frequency choice will likely have much to do with laws governing the RF spectrum in your area.

Check out this site for ideas (and even legal implications):

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the receiver is mobile with in a arena of 3*3 square meter area. my actual application is to run a autonomous line follower (which has two 1w motors) by wireless power transfer. i am experimenting this in an area which has neither any public establishments nor any other radio transmitter installed. i can also mount more antenna around the arena for better coverage. it would be better if it cover more distance, but the minimum requirement is 3 meters.

but i want to know the relation between frequency and received power.

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A transmitter for power transmission is likely to need a directional antenna.
The use of MOSFETS is excellent and 5 watts is not a problem either. A single band transmitter will be best and perhaps a crystal oscillator to keep it stable. There is dont forget, the legal requirement for a license for it as it can disrupt other services. Now you mentioned darlington transistors. These are not suitable for RF. A good start would be to have a transistor crystal oscillator, and buffer amp followed by a single ended class C MOSFET amplifier. I suggest a PD55008 by ST. If you need more information pleasse ask.
You did not mention frequency range. That will determine what components are needed
Are you trying to duplicate some of Teslas experiments?.

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i would design the circuit on a perforated board(vero board). thus the wire stray capacitance * would *limit the higher frequency use. i know that E=hf. higher frequency means higher energy. but does it mean that higher frequency transmits higher power? i exactly wants the relation between frequency used and power transmitted. sir please specify the components required, and few details of power amplifer used. whether i would choose a Marconi type antenna or a yagi( parabolic antenna construction is difficult)? my actual application is to run a autonomous line follower (which has two 1w motors) by wireless power transfer. i am experimenting this in an area which has neither any public establishments nor any other radio transmitter installed.

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please choose any frequency so that it would not be affected by wire stray capacitance and interectrode capacitance.

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Try the ARRL amatuer radio handbook You can still purchase these believe it or not Or amatuer radio sites

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I would like you to read some thing more about Testla experiment as people have mentioned
and What you are looking for the amount of wireless power transfer depends lot of parameters
and Also you have to go thru regulation requirement as well
Friis equation will give you a better idea for what you need to do

http://en.wikipedia.org/wiki/Friis_transmission_equation

This is a basic idea for what you need to select for in terms of frequency , antenna and distance

I hope this helps

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Here is a very good link which has good explanation, theory y plus practical experiments

http://www.powerlabs.org/plasmaglobes.htm

Looks like fun : _ The days i can remember which made learning interesting with good group involvement and kept class attention instead of the boring put you to sleep lectures

Here is another link for you if you like that type of science

Also interesting
http://www.coilgun.info/levitation/home.htm

or

http://www.harrington.force9.co.uk/SciencePhysics/Induction%20Heter/High%20Frequency%20Induction%20Heating.htm

If you want more of those type of links goto my home page at this address

http://www.harrington.force9.co.uk/SciencePhysics/Science.htm

Or this link stuff you dont see in class rooms anymore

http://www.coe.ufrj.br/~acmq/electrostatic.html

How to build these magnificant machines

Or you might like this

Real fun

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There is also this site as well quite good

http://www.mos.org/live-presentations/lightning

http://en.wikipedia.org/wiki/Van_de_Graaff_generator

This is where you can buy the belts from i would have thought Indian rubber would be quite good as well for this and a couple of dog bowls tied together to form the dome

Any way theres another link for you
http://www.ensalco.com/urabelt/vandegraffinfo.asp

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And some more Tesla sites with Jacobs ladder etc

http://www.tesla-coil.com/

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Consider that wireless energy transmission has possible health issues. Consider the implications of the electrical system in your body exposed to medium to high density RF energy — is there no affect? Consider that even subtle affects can be significant. Not to mention the cooking power of RF — have you ever touched the antenna out of a 60W 40M CW transmitter while it is keyed? I have — burnings to the bone!!