Mechanical Phase Shift by Moving a Dielectric Block in the Divider for Single-layer Slotted Waveguide Arrays

1. Introduction This paper proposes beam scan by moving dielectric blocks mechanically in the feed waveguide of single-layer slotted waveguide arrays as shown in Fig.1. Millimeter-wave antennas with beam scan are desired in various systems such as collision-avoidance car radars [1-3]. Electrical scanning is the best but mechanical one is still attractive in terms of cost, efficiency, heat-radiation and reliability if the antennas and the movable parts are light in weight and small in size. Single-layer slotted waveguide arrays [4] are planar antennas that keep high efficiency at a range of high gain even in millimeter-wave band and have simple structure suitable for mass production. This array with mechanical scan is a candidate in the above-mentioned point of view. Previously, we discussed mechanical phase shift by a movable metal plate in the power divider of the feed waveguide [5]. An amount of 86 degrees were obtained experimentally at 4GHz band, which corresponded 10-degree beam shift. However the metal plate for this phase shift was so long that the design including the adjacent coupling windows was required. In this paper, the metal plate is replaced with a dielectric block. The size of the block can be reduced to 42.3% of the length of the metal plate for equal amount of phase shift at 4GHz band. The reduction is enough for the block to be designed alone.