Slow-wave substrate integrated waveguide with partially polyline loading

In this letter, a novel slow-wave substrate integrated waveguide (SW-SIW) structure partially loaded with microstrip polyline is presented and experimentally demonstrated, and some interesting slow-wave propagation effects are obtained. The SW-SIW enables the cutoff frequency reduction without sacrificing its performance at the same lateral dimension. Specifically, with different central microstrip widths, a cutoff frequency reduction of 16%, 26%, 31% are achieved compared to the conventional SIW counterpart at the same lateral dimension. At the same time, the guided-wave phase velocity is reduced linearly as well, which could be easily realized and appropriate for phase shifters with uniform size at the feeding networks.