Plenary
Will We Ever Communicate via Evanescent Wave?
Conventional antenna arrays typically have a planar Cartesian structure with half-wavelength spacing between antennas. So far no one has made a convincing case for closer spacing or for a 3D structure. Propagating (homogeneous) plane-waves have a maximum wavenumber in any direction of two-pi-over-lambda, for which half-wavelength spacing provides Nyquist sampling. Shorter spacing enables the creation of evanescent (inhomogeneous) plane-waves, which have a horizontal (e.g., parallel to the array) wavenumber greater than two-pi-over-lambda, and an imaginary-valued wavenumber normal to the array. Normal to the array, evanescent waves decay exponentially fast and carry only reactive power. However, parallel to the array, evanescent waves can transport real power and they do not decay exponentially. In principle, evanescent waves can be harnessed for super-directive gain – but in end-fire operation only. To create evanescent waves in any arbitrary direction would require a 3D array. In short, everyone has been looking in the wrong direction to observe the possible benefits of sub-half-wavelength spacing.
Thomas L. Marzetta is Clark Distinguished Chair Professor in the ECE Department of the University of Maryland. Born in Washington, DC, he received the PhD and SB in Electrical Engineering from Massachusetts Institute of Technology in 1978 and 1972, and the MS in Systems Engineering from University of Pennsylvania in 1973.
He was a Distinguished Industry Professor at NYU Tandon School of Engineering, ECE Department from 2017 until 2025, and director of NYU WIRELESS.
Prior to joining NYU he had three industrial research careers: petroleum exploration (Schlumberger-Doll Research, 1978–1987), defense (Nichols Research Corporation, 1987–1995), and telecommunications (Bell Labs, 1995–2017). At Bell Labs he directed the Communications and Statistical Sciences Department within the former Mathematical Sciences Research Center, and he was made a Bell Labs Fellow. He originated Massive MIMO, the most spectrally efficient wireless scheme yet devised and a foundation of the fifth generation of wireless. He is lead-author of the book “Fundamentals of Massive MIMO”.
Marzetta was elected a member of National Academy of Engineering in 2020. Additional recognition includes the 2025 IEEE Eric E. Sumner Award, the 2019 Radio Club of America Armstrong Medal, the 2017 IEEE Communications Society Industrial Innovation Award, the 2015 IEEE W. R. G. Baker Award, the 2014 GreenTouch 1000x Award, the 2013 IEEE Guglielmo Marconi Prize Paper Award, and the 1981 IEEE Acoustics, Speech, and Signal Processing Society Paper Award . He was elected a Fellow of the IEEE in 2003 and he received an Honorary Doctorate from Linköping University, Sweden, in 2015