A Single-Switch-per-Bit Topology for mmWave and THz Reconfigurable
Reflective Surfaces
Abstract
We present novel multi-bit unit-cell topologies for reconfigurable
reflective surfaces –RRSs– (e.g., reflectarray antennas) with compact
designs for millimeter-wave and terahertz (mmWave/THz) applications.
Typically, mmWave/THz RRSs utilize one or multiple
single-pole-single-throw (SPST) switches leading to single- or dual-bit
modulated surfaces. These surfaces utilize the switches to manipulate
the phase of the imping waves, beamforming the reflected waves to the
desired direction. As such, RRSs are leveraged either for imaging or
wireless communication applications, which typically require the
formation of a single beam (no grating lobes) and high gains. The gain
and quantization lobe levels of an RRS is strictly related to the number
of phase bits utilized in the unit-cell. Explicitly, more phase bits
lead to lower quantization errors and better maximum gain/aperture
efficiency. However, increasing the number of phase bits requires more
SPST switches integrated within the unit-cell, leading to complex
designs with high RF losses. Herein, we present, for the first time,
RRSs with up to 4 phase quantization bits (16 states) that maintain one
switch-per-bit topology thus retaining a low-complexity design. The
proposed RRSs is presented alongside a series of analytical and
full-wave simulated results.