  Metamaterial-based reconfigurable holographic surfaces (RHSs) have been
proposed as novel cost-efficient antenna arrays, which are promising for
improving the positioning and communication performance of integrated sensing
and communications (ISAC) systems. However, due to the high frequency
selectivity of the metamaterial elements, RHSs face challenges in supporting
ultra-wide bandwidth (UWB), which significantly limits the positioning
precision. In this paper, to avoid the physical limitations of UWB RHS while
enhancing the performance of RHS-based ISAC systems, we propose a multi-band
(MB) based ISAC system. We analyze its positioning precision and propose an
efficient algorithm to optimize the large number of variables in analog and
digital beamforming. Through comparison with benchmark results, simulation
results verify the efficiency of our proposed system and algorithm, and show
that the system achieves $42\%$ less positioning error, which reduces $82\%$
communication capacity loss.
