  Dynamic metasurface antennas (DMAs) arise as a promising technology in the
field of massive multiple-input multiple-output (mMIMO) systems, offering the
possibility of integrating a large number of antennas in a limited -- and
potentially large -- aperture while keeping the required number of
radio-frequency (RF) chains under control. Although envisioned as practical
realizations of mMIMO systems, DMAs represent a new paradigm in the design of
signal processing techniques (such as beamforming) due to the constraints
inherent to their physical implementation, for which no complete models are
available yet. In this work, we propose a complete and
electromagnetic-compliant narrowband communication model for a generic DMA
based system. Specifically, the model accounts for: i) the wave propagation and
reflections throughout the waveguides that feed the antenna elements, ii) the
mutual coupling both through the air and the waveguides, and iii) the insertion
losses. Also, we integrate the electromagnetic model in the conventional
digital communication model, providing a complete and useful framework to
design and characterize the performance of these systems. Finally, the accuracy
of the model is verified through full-wave simulations.
