RF Energy harvesting for mobile phone charging

Is there any implemented model and circuit of an RF energy harvesting circuit to charge a mobile phone?

Thanks in advance :)

http://www.powercastco.com/
http://energous.com/

Wireless phone charging systems like Qi uses a transmitter power of several Watt at a maximum distance of a few centimeters.

If you look at energy harvesting (using RF that is transmitted anyway), the harvested power is maybe a few mW, in an optimistic scenario. What is the standby power consumption of your phone?

Is it the signal strength ? It is -93 dBm
If not how do I find it out ?

0dBm is 1mW
-93dBm is 0,0000000005 mW

If your rectifier has 100% efficiency (it is less), do you want to charge the phone with a power of 0,0000000005 mW ?

It's not "harvesting" if you bought it yourself (wireless charging
schemes involving a transmitter).

If you intend to "harvest" ambient RF energy then you're looking
at dismal economics (unless you are an academic or an early
rounds funding-seeker, both of these getting paid by an
alternate route).

I wanted some resources that could help me in building one myself or some previous practically implemented research work

The old-fashioned 'crystal radio receiver' needs no power source. It is driven by the radio station's broadcast. If you are close to a transmitter you may generate enough voltage to run your project.

Crystal radio needs a long wire antenna and an earth ground.
Maybe for higher frequencies an ungrounded dipole or other
differential antenna could work. Crystal radio also needs a
very high impedance earpiece and even then is barely audible
(going by recollection from my distant youth, when I was
too broke for buying batteries on the regular, and saved up
for one from the back of Boy's Life magazine).

At any rate there is the issue of tolerable physical envelope,
lying behind the "can it work at all?" basics. The wireless
charging folks are all over that problem. But they have a
transmitter.

You can "feed" your mobile phone with multiple energy sources, like: portable wind turbine generator, small solar power panel, or even a walking power generator.

https://www.amazon.com/Turbine-Gener.../dp/B00ALLUEA4
https://www.ebay.com/itm/19W-Semi-fl...-/162866473738
https://www.bionic-power.com/

You look like Iron Man but you can make long calls wherever you are