Ding Nie and Bertrand Hochwald from the University of Notre Dame developed new bandwidth bounds for coupled loads that are applicable to MIMO communication systems. Electromagnetic coupling between antennas can benefit bandwidth. They define a power reflection ratio to measure matching for coupled loads and derive a bound on bandwidth in terms of the poles and zeros of the load's scattering matrix. Applying the bound, they show that coupling can maximize bandwidth at around a quarter wavelength spacing for dipole antennas. Broadband matching networks are needed to achieve the bounds for coupled antenna designs.