Parity-Time Glide-Symmetry and Third Order Exceptional Degeneracy in a Three-Way Microstrip Waveguide

A microstrip-technology three-way waveguide has been conceived to display exceptional modal degeneracy in the presence of periodic gain and radiation losses satisfying parity-time (
$PT$
) glide-symmetry. A third order exceptional point of degeneracy (EPD) is obtained in the modal dispersion relation, where three Floquet-Bloch eigenmodes coalesce at a single frequency, in their eigenvalues and polarization states. In the proposed structure,
$PT$
-glide-symmetry is achieved using periodically spaced lumped (radiation) loss and gain elements, each shifted by half a period. This particular degeneracy can be utilized in the design of devices such as radiating arrays with distributed amplifiers, arrays of oscillators, and sensors.