Tunnel emitter: tunnel diode based low-power carrier emitters for backscatter tags

Backscatter enables transmissions at orders of magnitude lower energy consumption when compared to conventional radio transmitters. Backscatter tags achieve this by the reflection or absorption of carrier signal generated from emitter devices. However, backscatter systems are limited by these emitter devices, as they are significantly energy-expensive when compared to the tags. While backscatter tags can operate without requiring batteries, relying on the minuscule amounts of energy harvested from the ambient environment. However, the emitter devices, are commonly tethered to an external power supply or operate on large batteries.

We present Tunnel Emitter: a tunnel diode oscillator based system that enables the generation of carrier signals at a peak biasing power of tens of µW. Thus, for the first time, it allows battery-free emitter devices. The key enabler to the design is a phenomenon exhibited by tunnel diode oscillators that we call back injection, and we are the first to demonstrate. Back injection enables the emitter devices to amplify (up to 20 dB) and relay the backscattered signal. Our results show that Tunnel Emitter when operating together with a tag from long-range backscatter system, facilitates multifloor communication. Tunnel Emitter, due to the back injection phenomenon, achieves this with a carrier signal that is orders of magnitude weaker than used in state-of-the-art systems. We believe Tunnel Emitter overcomes the key constraint restricting backscatter systems and thus can make backscatter systems ubiquitous.