Planar slotted ridged waveguide antenna arrays with dielectric layer

The paper simulates the options available to move operating range of slotted waveguide antennas downward in frequency without changing the waveguide cross-section, and suggests the ways for designing linear waveguide-slotted elements based on rectangular and ridge waveguides with air and partial dielectric filling. The critical frequency of the fundamental mode of a 16x8 mm rectangular waveguide moves by ridging from 9.5 to 6.5 GHz. Partial dielectric filling of the cavity of the ridge waveguide makes it possible to additionally shift the operating range downward in frequency by 6-10% without making changes to antenna design. The antenna characteristics of linear arrays based on a dielectric-filled ridge slotted waveguide have been compared in terms of gain and voltage standing wave ratio to similar designs of arrays on rectangular and air-filled analogues. Based on the obtained structures of linear elements, simulation models of planar arrays have been constructed so that they have the similar area of total surface. Simulated frequency dependence of the realized gain for planar arrays has demonstrated a shift of the operating range downward in frequency. The analysis of the directivity characteristics of planar arrays for various phase shifts between the linear elements has been carried out. The simulation results have shown that the use of a dielectric-filled ridge waveguide gives an advantage in phase scan angle of the main beam of the radiation pattern. With the same phase shift, in planar arrays of dielectric-filled ridge waveguides, the main beam scans for a larger angle while keeping side lobes at low level. Thus, the use of a ridge slotted waveguide with a dielectric layer inside makes it possible to expand the phase scan angle.