Huygens’ Meta-Waveguide With Arbitrarily Reduced Cutoff Frequency

We present a simple yet effective method for realizing compact waveguides that support efficient below-cutoff propagation with user-defined modal characteristics. The design incorporates a Huygens’ metasurface (HMS) as one of the waveguide walls, engineered to transform a cutoff mode into a propagating one by satisfying suitable boundary conditions. By tuning the metasurface’s local electric and magnetic responses, the propagation constant can also be independently controlled. We validate this concept both numerically and experimentally around 4 GHz in a waveguide of height 15 mm, well below the 10-GHz cutoff of a conventional counterpart, and show that it supports user-defined phase constants.