  We show the physical realization and experimental demonstration of an
exceptional point of 6th order degeneracy in a triple ladder (or three-way)
microwave waveguide realized using three coupled microstrips on a grounded
dielectric substrate. This threeway waveguide supports six Bloch eigenmodes and
all coalesce onto a degenerate single eigenmode at a given frequency. The
three-way waveguide is gainless, and this exceptional point is associated to a
vanishing group velocity and its multiple derivatives. Indeed the
wavenumber-frequency dispersion diagram, that we call 6th order degenerate band
edge (6DBE) has six coalescing branches. We provide the experimental
verification of a 6th order exceptional point by evaluating the degenerate
wavenumber-frequency dispersion diagram from the measurement of scattering
parameters of a six-port unit cell. We also show the resonant behavior of a
cavity made of the three-way waveguide with finite length. The unique
properties of 6DBE can be exploited in designing innovative high-Q resonators,
oscillators, filters, and pulse shaping devices.
