Design and characterization of periodically-loaded substrate integrated waveguide phase shifters

A substrate integrated waveguide (SIW) phase shifter with tuning capability is introduced in this paper. Transverse slots are placed on the top plane of an SIW and loaded with capacitive elements. This structure has a periodic topology thus exhibits electromagnetic bandgap (EBG) properties. It is shown that the slots can be properly designed to avoid radiation loss. As well, the relationships between transmission characteristics and design parameters such as capacitor value and slot size are investigated through parametric simulations. Several phase shifter prototypes with 6 unit cells were fabricated and evaluated using S-parameter measurements. A very good agreement is observed between measurements and simulations. It is demonstrated that the proposed phase shifter provides the phase tuning range of 230.1° at 15 GHz and yields a ±5° phase bandwidth of 32.5% for the case of 0.3-pF loading capacitor.