Mirror Scanners for Panoramic Millimetre Wave Radars

To ensure that a vehicle mounted panoramic radar continues to illuminate the ground even in the case of base motion (roll and pitch) it is necessary to broaden the elevation beamwidth to generate a fan beam and maintain a reasonable swath width. This paper examines methods to achieve this for a 94 GHz swash plate scanner. Because of their rotational symmetry, swash plate scanners with flat mirrors produce pencil beams so some mechanism to widen the beam in elevation is required. This paper examines various methods to achieve this and concludes that shaping the mirror is the best option. A simple PCAAD-6 model was developed to predict this elevation beam spread based on the mirror curvature. Measurements were then made using both smoothly curved and stepped zone-plate mirrors that confirm the good accuracy of the predictions.