QPSK-modulation Wireless Transmitter Based on Time-domain Coding Metasurface

In this paper, a wireless communication system based on time-domain digital coding metasurface with Quadrature Phase Shift Keying (QPSK) modulation is proposed. The aperture-coupled resonant rings on the metal patches of the metasurface elements create an asymmetry along the x-axis, resulting in a phase difference. The Field Programmable Gate Array (FPGA) is used to change the conduction and cutoff states of pin diodes, which can control the phase responses of the metasurface elements, forming four coding states. Within a certain period, the FPGA dynamically modulates the high and low levels, thus controlling the reflection characteristics of the metasurface. When the information is converted into a binary bitstream and written into the FPGA, represented by high and low levels, the baseband signal is modulated onto the carrier by the metasurface. This system replaces the functionality of mixers in traditional wireless communication systems, further simplifying the architecture of wireless communication systems. The overall system is demonstrated by an experiment with a picture transmitted and received in real time, showing promise in future low-cost wireless communication transmission systems.