We present a method for the mitigation of
quantization lobes in single-bit reconfigurable reflective surfaces (RRSs).
Typically, RRSs are planar beamforming structures consisting of hundreds or thousands
of antennas with integrated tunable switches. Under plane-wave illumination,
single-bit RRSs suffer from undesired side lobes or quantization lobes, which
are caused by the periodicity of the errors due to the limited number of bits
used in phase quantization. In this work, we present a topology that suppresses
the quantization lobes using single-layer, 1-bit RRSs, by implementing a fixed
but random phase delay in every unit-cell. The introduction of phase
randomization breaks the periodicity of the quantization errors, thus reducing
the quantization lobe level (QLL). We carry out a theoretical analysis to
demonstrate the effect of phase randomization in RRSs, and for the first time,
provide the condition for choosing the range of randomization required to
achieve the lowest sidelobe level (SLL). Leveraging this condition, we design a
single-layer, 1-bit 30×30 randomized RRS at 222.5 GHz. The reflective surface
is fabricated on a thin, low-loss alumina ribbon ceramic wafer from Corning Inc.
using a simplified fabrication technique suitable for large-scale production of
mmWave/THz RRSs. Finally, we present the radar cross-section (RCS)
characterization results obtained from a quasi-optical measurement setup
validating the mitigation of quantization lobes using the proposed
randomization technique.
Implantable computer-controlled adaptive multielectrode positioning system