Radiated Power ?
The energy is transferred with a pure magnetic field, not to be confused with radiative systems or radio waves.
The effective radiated power, responsible for the range of radio’s, originates from the far-field component from the magnetic and electric fields.
With Wireless Energy, these far-fields and the radiated power are almost zero, far below the RF-radiation limits for industrial equipment.
One of the design challenges of antenna’s for wireless energy, is generating strong local magnetic fields, while the remote field is far below the EMC-limits on any harmonic frequency.
Electric power is coupled from transmit-coil to receiver-coil by pure inductive coupling.
The coupling-factor, defined as the part of the transmit-flux which passes at the receiver-coil, can be very low compared to transformers, usual between 1% and 10%.
The low coupling-factor is compensated with low loss, or resonance with high Q-factors in both coils.
With precise matching of the coils the power-efficiency is substantially higher than the coupling-factor.
Total power-efficiencies of 90% can be achieved with coils at a distance approximately equal to their size.
Comparable with Qi or PMA ?
With these popular Wireless-energy standards, the coils are not tuned in resonance. These systems are like switching converters, where the transformer is split apart in 2 parts, primary and secondary. A necessary high or fixed coupling-factor limits the distance between the primary and secondary coil of the transformer in both parts.
Our wireless-energy solutions operate at one fixed frequency where resonance with high Q-factors is a part of the system.
Our antenna’s are made for a larger range with lower coupling-factors, and are not compatible with the standards.
Magnetic resonance not only compensates the effects of low coupling-factors, but also limits the emission-spectrum to one single working-frequency, where the harmonics originating from drivers and rectifiers are filtered.
At ISM-frequencies like 6.78MHz and 13.56MHz more radiation and magnetic fields-strengths are possible without interference to other systems.
The power from the magnetic field is only available within a limited distance around the antenna. This range is determined by its size and shape. Outside this range the field-strength will decrease rapidly with distance in the 3rd or 4th power, as long as the effective radiated power is zero. At a distance equal the size of the antenna´s, an overall power-efficiency of 90% or better is possible, and with 50% efficiency, the distance may be a multiple of that.
With advanced antenna-design, the magnetic field can be zero at specified distances and directions, to prevent unwanted couplings to sensitive electronics.
We can make wireless-energy systems for any distance, greater than antenna-size, and different from any standard.