A 43.2 μW 2.4 GHz 64-QAM Pseudo-Backscatter Modulator Based on Integrated Directional Coupler

This paper proposes a 2.4 GHz ultra-low power pseudo-backscatter modulator with an integrated directional coupler for wireless sensor network applications. In order to improve the performance of backscatter modulator for multilevel modulation, an integrated directional coupler is employed to isolate the radio frequency carrier wave from the modulated signal. As a result, the carrier wave can be modulated in radio frequency domain independently without being affected by reflection coefficient of a conventional backscatter modulator. For further reducing power dissipation, the modulator only employs buffers for output and implements modulation by passive circuits. The proposed modulator is demonstrated in a standard 40 nm CMOS 1P10M process and it achieves 64-QAM modulation at 3 Mb/s data rate by consuming only 43.2 μW with a supply voltage of 0.8 V.