Metasurface-Based Spatial Phasers for Analogue Signal Processing

A dispersive delay structure, or phaser, is an integral part of analogue signal processor. A phaser is a circuit, whose group delay can be engineered to obtain the desired response as a function of frequency. Traditionally, phasers have been implemented in circuits or waveguide structures, but they can never deal with electromagnetic waves in free space due to limitation of natural materials. To resolve this drawback, a novel metasurface-based structure, spatial phaser, for analogue signal processing in the spatial domain is proposed. A general design theory is put forward to realize the spatial phaser for manipulating the dispersive delay of electromagnetic waves. To demonstrate this method, three spatial phasers with different group-delay responses are elaborately devised and a prototype that exhibits a positive-triangular group delay from 8 to 10 GHz is fabricated. The experimental and simulation results show good agreement. This work will facilitate the development of real-time analogue signal processing in spatial domain for applications in radars, electronic countermeasures, and other related areas.