Google wants its self-driving cars to be wireless, too. Recently uncovered Federal Communications Commission documents suggest that Google's parent company Alphabet is testing out wireless charging for its self-driving cars.

The filings hint that Google is keen on completely cutting the autonomous cars' charger cables and replace them with wireless charging systems.

The documents show that two companies recognized for wireless vehicle charging have obtained FCC's authorization to set up such charging systems at the firm's headquarters in Mountain View, California.

Hevo Power, a startup from New York, initially sent its systems in February last year. Similarly, Momentum Dynamics, which is headquartered in Philadelphia, Pennsylvania, got permission to deliver their chargers for installation later in July. The former allegedly sent its prototype charger named Alpha while the latter's system was not mentioned in the documents.

What's interesting is the address on Momentum Dynamics' filing matches the secretive X division in which Google's autonomous cars are presently being made. According to IEEE Spectrum, Google is already testing chargers from Momentum Dynamics at its headquarters in Mountain View and at the Castle Commerce Center, which is the former United States Air Force base, in Atwater.

Reportedly, the charging systems beam up energy originating from a transmitter set in the ground to the receiver on the underneath of the driverless cars, by means of the resonant magnetic induction principle.

The FCC document [pdf] says that Hevo's prototype charger delivers "1.5 [kilowatts] of power from the wireless power transmitter to a wireless vehicle receiver." Momentum Dynamics, however, says that it has already produced wireless transmitters with power ratings of up to 200 kilowatts.

Hevo Power and Momentum Dynamics have yet to confirm their participation in the development of Google's driverless cars.

To date, there are already wireless charging products intended for electric vehicles such as the Chevy Bolt and Nissan LEAF.

In the meantime, we earlier reported that Google is all set to test its autonomous cars in Kirkland, Washington later this month. This makes Kirkland the third city in the U.S. to host Google's testing of its self-driving cars, next to Austin and Mountain View.