Terahertz Massive MIMO System Evaluation with Virtual Antenna Arrays at 300 GHz

This paper presents an experimental study of a terahertz (THz) massive MIMO (M-MIMO) system utilizing virtual antenna arrays in indoor Line-of-Sight (LoS) environment. Using a VNA-based THz measurement system with a 60 GHz bandwidth spanning 240 GHz to 300 GHz, we emulate a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">25× 25</tex> THz M-MIMO system by creating <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5× 5</tex> uniform planar arrays (UPA) at both transmit and receive sides, with half-wavelength inter-element spacing, similar to scenario-generic on-chip antenna arrays. The system is evaluated by assessing the MIMO channel capacity and correlation while also exploring some sub-array configurations towards inter-element spacing optimization. The analysis demonstrates strongly correlated channels accompanying the employment of the system in the multipath-poor LoS environment, which highly decrease the achievable system spectral efficiency compared with shannon upper bound. A minor capacity enhancement ratio of about 1.8 is achieved by employing all systems antenna elements with a maximum channel capacity of 1019 Gbps. This study presents a first experimental evaluation of such large-scale MIMO system implementing virtual antenna array concept in the WR-03 frequency band.