  Within the framework of tight binding models, aperiodic systems are mapped to
a renormalized lattice with a dimer defect. In models exhibiting
metal-insulator transition, the dimer acts like a resonant cavity and explains
the existence of the ballistic transport in the system. The localization in the
model can be attributed to the vanishing of the coupling between the two sites
of the dimer. Our approach unifies Anderson transition and resonance transition
and provides a new formulation to understand localization and its absence in
aperiodic systems.
