Harmonic Reflection Amplifier for Widespread Backscatter Internet-of-Things

The highly power-efficient backscattering communication scheme holds solid potentials to lead the Internet of Things technologies. However, the asymmetric radio frontend architectures that ensure cheap and pervasive communicating things and tags at one end of the link, overburden the other end of the link (“reader”) with complicated and expensive hardware. This turns out to prevent the integration of the technology in the wide spectrum of consumer electronic devices (e.g. RF smartphone platforms). By separating TX and RX frequency bands, the harmonic backscattering scheme drastically loosens the technological constraints toward integration. We propose here the use of a single tunnel diode to build a harmonic reflection amplifier (HRA), using the nonlinear behavior of the negative differential resistance region to both generate harmonics and amplify the signals. The circuit also behaves like a common backscatter, with the same-frequency backscattering modulation for operation with legacy readers. Operating below 150 mV, the HRA drains 144-μW dc power with a measured positive conversion gain of 18 dB.

I. Introduction

With the emergence of the fifth-generation (5G) technologies, the year 2020 came across 30 billion connected devices, or 5.1 connected devices per person on average [1], which anticipates a proliferation of Internet-of-Things (IoT) platforms that could range from small portable electronics devices such as smartphones and sensors to large electric vehicles. Backscatter communication is a promising technology toward true ubiquitous IoT, as it simplifies the many “thing” complexity [2]. In this asymmetric communication scheme, the RF signal is generated on one side only (the reader), whereas the tag backscatters the modulated signal to the reader with identification and other preferred information [3].