DESIGN AND ANALYSIS OF A 35 GHz 8×8 MIMO ANTENNA ARRAY FOR MILLIMETER-WAVE APPLICATIONS

Abstract

Millimetre-wave (mm Wave) communication systems operating in the 30 300 GHz spectrum range are key enablers for high data rate applications in 5G FR2 and emerging 6G technologies. However, antenna design at these frequencies is faced with a number of challenges such as high conductor losses, narrow bandwidth, low radiation efficiency and high mutual coupling in multi-element MIMO configurations. These limitations hinder the development of compact and high-performance antenna systems for practical applications. In this work, we tackle these challenges by introducing a dielectric resonator-based MIMO antenna architecture which can achieve wide bandwidth, high efficiency and better isolation at 35 GHz. For solving these problems, a microstrip fed cylindrical dielectric resonator antenna (CDRA) with parasitic metallic caps is proposed. The dielectric resonator reduces conduction losses and the parasitic caps enable multi-mode excitation to enhance the bandwidth. The antenna is designed with RT5880LZ dielectric material on a RO4450B substrate and optimized by using full-wave electromagnetic simulations in CST Microwave Studio. The methodology includes unit antenna design, parametric optimization of important geometrical parameters and extension to multi port MIMO system. Each MIMO channel is realized with a 4-element CDRA sub array as a single radiating element and eight such sub-arrays are independently excited to realize an effective 8×8 MIMO configuration. The optimized antenna has a return loss up to -72.9dB and wide impedance bandwidth of 30.9GHz-39.5GHz, which indicates a good impedance matching. High radiation efficiency of about 97% is obtained with stable far-field radiation characteristics. The MIMO system exhibits very low envelope correlation coefficient (ECC) values in the range of 0.0001-0.018 and diversity gain close to 10 dB indicating strong spatial diversity and low mutual coupling. Isolation levels better than -10 dB at all ports further confirm good multi-channel performance. (iv) The designed antenna system is a good choice for 5G FR2 communication, early 6G wireless systems, automotive radar and high-capacity point-to-point links where wide bandwidth, high efficiency and compact multi-element designs are important. In the future, the gain and radiation performance can be further optimized by adding the Artificial Magnetic Conductor (AMC) or Electromagnetic Bandgap (EBG) structure to suppress the surface wave loss and improve the in-phase reflection characteristic. Moreover, the fabrication and experimental verification, as well as the exploration of advanced decoupling techniques and beamforming capabilities, can further boost the system performance and practical applicability.