How Far Is Far? How to maximize wireless power delivery at a distance and minimize energy loss

The answer to optimization and efficiency is retrodirective, radio-frequency-based wireless power delivery.



The question on people’s minds these days with regard to sending power over air is not, “does it work.” Rather, it’s “which wireless power system works the best?” Specifically, we’re hearing questions concerning:

  • Long range vs short range wireless power transmission
  • Power loss over a distance
  • How FCC and other country regulations affect the reach of wireless power
  • The efficiency of retrodirective wireless power delivery using radio waves

Here’s a quick response to each topic.

Long range vs short range wireless power transmission

Charging pads (or Qi charging) have long been considered short range wireless power transmission. A device with a magnetized coil inside rests on or within inches of a transmission pad (or bowl or surface), and the charging begins. Smartphones, electric toothbrushes, digital watches, and more have used this technology for years. But it’s not too much different than plugging in to a USB port. This is very short range.

Longer range wireless power works on radio waves, much like wifi. Devices can be several feet away from a Power Hub, in use, and on the move and still receive power. Using Cota Real Wireless Power as an example, devices can be up to 30 feet from a Power Hub and still receive meaningful levels of power. There can even be walls and other objects in between. Again, much like how wifi works.

Power loss over a distance

Also like wifi, the further you get from the Power Hub (or modem), the weaker the transmission. But in the case of wireless power like Cota, there’s a fix. Cota Power Hubs can be placed anywhere and linked to ensure an efficient and reliable transmission across large spaces, like warehouses, airports, and resorts.

Cota-enabled devices that move out of range from one Power Hub source automatically connect with the next one. No user input required. No interruptions.

How FCC and other country regulations affect the reach of wireless power

The FCC and other countries’ regulatory bodies regulate how far certain technologies can deliver power wirelessly. Cota Real Wireless Power is the only technology that has been globally approved for use at any distance, even when people are present.

Organizations that adopt the Cota system do not need to worry about reach limitations.

The efficiency of retrodirective wireless power delivery using radio waves

Leveraging the innate efficiency of retrodirectivity is what makes Cota so uniquely efficient. IGI Global defines the physics concept: “A retro-directive array is capable of re-transmitting an interrogating signal back to its source without requiring a priori knowledge of its direction of arrival (DoA) or any signal processing.”1

Hatem Zeine, physicist, inventor, and founder of Ossia, has written a couple in-depth articles explaining the science:

Not All Wireless Power Is Created Equal: Retro-directivity vs. Beamforming

How to Make Wireless Power at a Distance Possible

In short, retrodirectivity is the most effective way to send power over air because it:

  1. “Instantaneously determines the phases of the transmitter to deliver power to the device.
  2. Repeats the beacon many times per second to track any motion of the device
  3. Reacts to people walking to the signals, and adjusts instantly.
  4. Feeds the receiver through most optimal paths.”
  5. Works in non-line-of-sight situations.2

Other systems use complex algorithms to ensure a safe connection and safety that slow the transmission process down. Retrodirectivity eliminates the need for these complexities.

If you’re looking for an engineer’s perspective of how the Cota system works at a distance, consider reading Rethinking Wireless Power: A Closer Look at Ossia's Technology by Lee Goldberg of ElectronicDesign.

How far will your products go with Cota Real Wireless Power? Contact us. We’re here to answer your questions.