Apple's AirPower wireless charger feels like a relic from an earlier age, which gives an idea of how fast things move in the tech sector. In fact it was announced less than four years ago - in September 2017 - and officially cancelled in March 2019.

But rumours continued to follow the project. In March last year it was reported that Apple was re-engineering the device, and only last month Bloomberg's Mark Gurman claimed the company was developing a wireless charger along the same lines as AirPower.

Now a new patent has emerged that adds fresh fuel to rumours about the charger that won't die. The patent is called Wireless power system with device movement detection and was registered in February 2020, and spotted by AppleInsider.

It describes technology to enable a wireless charger to handle devices that are moved around on its surface. If they are lifted off the plate, power is shut off; but if they merely move across its surface, power remains on.

"In response to the wireless power receiving device being lifted away from one or more coils, the control circuitry causes the inverter circuitry to halt wireless power transmission; and in response to at least one movement of the wireless power receiving device along the charging surface, the control circuitry does not cause the inverter circuitry to halt wireless power transmission," the patent reads.

"When movement is detected, appropriate action can be taken. For example, the control circuitry may use coil inductance measurement circuitry to gather updated coil inductance measurements. By analysing the coil inductance measurements, the control circuitry can determine which coils to switch into use in transmitting the wireless power to the wireless power receiving device."

This is one of the major problems that AirPower tried, and failed, to solve - namely to be able to put a device anywhere on a charging plate and not have to place it on a specific sweet spot.

Whether this patent will lead to a spiritual sequel to AirPower in the future remains to be seen. But if it does, you'll read about it first in our AirPower news hub.

This article originally appeared on Macworld Sweden. Translation and additional reporting by David Price.