Beam Steering in Narrow-Wall Slotted Ridge Waveguide Antenna Using a Rotating Dielectric Slab

A beam-steering technique in narrow-wall slotted ridge waveguide at X-band is proposed. An array of inclined slots cut in the narrow wall of a rectangular ridge waveguide is employed. Beam steering is achieved by rotating a dielectric slab inside the waveguide. The change of wavelength at different rotation angles of the slab is used as the phase shifter. To confirm the usefulness of this method, a short nonresonant 20-slot waveguide array antenna with an element spacing of d = 0.44λ0 has been designed, built, and tested. It is shown that the main beam can be steered from near broadside (0 = 6°) toward end fire (0 = 42°) by rotating the dielectric slab by 90°. A directivity variation of 2.8 dB and a half-power beamwidth increase of 3° are observed over this scan at the design frequency. The gain varies from 11.17 to 12.47 dB over the scanning range. Due to the relatively short length of the prototype, losses in the terminating load have limited the radiation efficiency to values between 43% and 86%. The E-plane radiation patterns measured at the operation frequency of 9.35 GHz and compared very well with the simulated results.