Such combined transmissions, sometimes called ‘swipt’ for ‘simultaneous wireless information and power transfer’, are proposed to interface one powered fixed point with multiple wireless IoT sensor nodes that no longer need local power sources.
Pulse position modulation is used in the scheme, and it involves “an integrated information decoder and energy harvester architecture where the received RF signal is first rectified before being used for information decoding,” according to the KMOU. “Such architecture eliminates the need for energy-consuming RF components such as local oscillators and mixers.”
The receiver (see diagram) has a rectifier diode at the front, so the signal is transmitted as a series of high amplitude pulses to make best use of the diode’s non-linear energy-harvesting characteristics while keeping average power low – Electronics Weekly has asked what the na(t) term and adder at the front end represent if there are no mixers.
Information detection requires no coherent technique, just finding the position of pulses with a certain symbol duration.
“Theoretical, numerical and experimental results highlight the benefits of the proposed PPM scheme,” said the university.
KMOU worked with Imperial College London.
The work was published as ‘Wireless information and power transfer for IoT: Pulse position modulation, integrated receiver, and experimental validation‘ in the IEEE Internet of Things Journal
Electronics Weekly feels the need to point out that such schemes tend to dissipate power at the transmit end.
