Exploiting Tunneling Reflection Amplifiers for Amplitude and Phase-Shift Keying Backscatter Communications

This paper proposes and explores the idea of using low-power reflection amplifiers, made with tunnel diodes, to perform amplitude and phase-shift-keying (APSK) modulation for backscatter communications. Past work used tunneling reflection amplifiers for backscatter range extension and binary-phase shift keying (BPSK) with two different voltage biasing states to generate one bit per symbol. It is advantageous to exploit the different reflection states from different applied biasing voltages to perform multi-bit backscatter communications. This work sweeps these amplifiers’ biasing voltages within a 225 mV range (below a maximum 300 mV of applied voltage) to modulate the amplifiers’ reflection coefficients and generate distinct APSK symbols from these coefficients for low-power backscatter communication applications. The implementation of APSK allows for the transmission of more than 1 bit per symbol. Unlike previous passive multi-symbol modulation schemes, the use of tunnel diode reflection amplifiers allows for creation of multiple symbols with just one device that can generate different load impedance states and reflection gains above 0 dB to allow for a greater range of magnitudes to place APSK symbols and extend read-ranges between tag/modulator and reader/receiver. These tunnel diode reflection amplifiers allow for scaling of modulation order and versatility of implementing different modulation schemes that are amplitude and phase-based.