<p>Space-time-modulated metasurfaces can manipulate electromagnetic waves
in space and frequency domain simultaneously. In this paper, an analytical design
of space-time- modulated metasurfaces with modulation elements composed of two
paths, In-phase (I) and Quadrature (Q), is proposed. The model is derived analytically,
<a>the space/frequency domain</a> manipulations are achieved
by designing the dimension and time sequence of I and Q paths.<a> In the specular reflection direction, an objective frequency
shift of the reflected first order harmonic can be obtained. While, in other
directions, the opposite first order harmonic can be easily controlled by
changing the dimension of I/Q paths and the objective first order harmonic
remains unchanged.</a> Furthermore, with a small dimension of I/Q paths, the
first order harmonic can be used for beam scanning by pre-designing the start
time of the modulation element. To realize the space-time-modulated metasurface
with the required periodically time-varying responses, 2-bit unit-cells loaded
with dynamically switchable pin diodes are employed as I/Q modulation. Both
analytical and numerical results demonstrate that space and frequency domain
manipulations of the reflected fields by the first order harmonics can be
simultaneously obtained. The proposed designs have potential applications in
wireless communications, radar camouflaging, and cloaking.</p>
Characterizing the polarization and cross-polarization of electromagnetic vortex pulses in the space-time and space-frequency domain
