Seattle: In a major breakthrough in the smartphone technology, researchers at the University of Washington have announced successful tests of a battery-free cell phone.The phone harvests radio wave energy from a wireless base station (such as Wi-Fi) and converts light through miniature photo-diodes. It used very low power (microwatts) to transmit back to the base station. As a result, the phone does not have a battery, and thus never needs to be charged.
The researchers demonstrated voice call and even skype calls using this battery-free phone.
However, at a time when a smartphone needs to be charged every day, and when third-world countries lack basic utilities such as electricity, a phone that requires no charging at all could have a significant social impact.
Instead, the battery-free cellphone takes advantage of tiny vibrations in a phone’s microphone or speaker that occur when a person is talking into a phone or listening to a call.
An antenna connected to those components converts that motion into changes in standard analog radio signal emitted by a cellular base station. This process essentially encodes speech patterns in reflected radio signals in a way that uses almost no power.
To transmit speech, the phone uses vibrations from the device’s microphone to encode speech patterns in the reflected signals. To receive speech, it converts encoded radio signals into sound vibrations that that are picked up by the phone’s speaker. In the prototype device, the user presses a button to switch between these two “transmitting” and “listening” modes.