# Wideband Lorenz Resonance Reconfigurable Metasurface for 5G+ Communications
###### Abstract  
Reconfigurable intelligent surfaces (RIS) have been considered as a promising solution to enhance the spectrum and energy efficiency of the 5G+ and future 6G wireless communication systems. The performance of RIS will become the key metric of these communication systems. In this paper, we proposed a wideband Lorenz resonance-based metasurface reconfigurable reflectarray (MSRRA) realization scheme with low energy consumption targeted at the center frequency of 28 GHz. A compact voltage bias network for the varactor diodes is carefully designed to reduce losses in RF current and the influence of the bias circuit on the radiating element effectively. An equivalent circuit model for the MSRRA unit cell is also introduced to predict the properties of the MSRRA system, which can be used to optimize the MSRRA design efficiently. In the experimental tests, the proposed MSRRA system can be optimized to cover a dynamic reflection phase range of over 300\({}^{\circ}\) with a bandwidth of 3.83 GHz, which is consistent with the simulation results. The measured single-scattering beam bandwidth is 1.85 GHz at the center frequency of 28 GHz, which can fully cover the whole n257 channel of 5G NR. The proposed continuous tunable MSRRA can support 5G+ and 6G indoor, short-range links, and outdoor point-to-point communications.  
reconfigurable intelligent surfaces (RIS); reflectarray; equivalent circuit model (EC); metasurface; radar cross section (RCS); scattering beam reconfiguration; transmission line (TL) +
Footnote †: journal: Electronics  
of the RIS unit cell in the millimeter-wave band is much smaller than the lower-frequency band, it is a great challenge for system design and integration [25; 26; 27]. Another system implementation issue that needs to be addressed is the high energy loss of RIS. When the unit cell of the RIS is working at the resonant frequency, it absorbs a large amount of energy of the incident electromagnetic wave and reduces the reflection efficiency of the RIS. In [28], it was reported that the attenuation at the resonant frequency is more than 10 dB and the attenuation difference between the maximum and the minimum exceeds 15 dB. With such a great attenuation loss and fluctuation in the bandwidth, the RIS communication efficiency degrades a lot. Moreover, the reported typical communication bandwidth of the single beam in current RIS based on resonance mechanisms at the millimeter-wave band is hundreds of megahertz [29], which is very limited and cannot meet the high data rate requirements in millimeter-wave communication systems. To overcome the problems addressed above, a wideband MSRRA realization scheme with low energy consumption is proposed as a reflector in this paper. An equivalent circuit model for the MSRRA unit cell is introduced to predict the properties of the MSRRA system. We have designed a compact integrated voltage bias network to support the system's optimization iteratively. The dynamic reflection phase-tuning range of the proposed MSRRA system can reach over 300\({}^{\circ}\) at a bandwidth of 3.83 GHz in the 28 GHz frequency band. The power consumption of our MSRRA is only about 2.8 W, which can work for about 4 h with a 12 V@1 Ah lithium battery. Scattering beam reconfiguration and a communication bandwidth as high as 1.85 GHz are obtained with the help of the well-designed DC-bias network and the tunable varactors soldered on the surface. With such a wide single-beam bandwidth, the aperture of the MSRRA can be greatly reduced and a significant increase in the data rate of the indoor RIS-aided communication system can be attained.