| 摘要 |
<p>A radar lens 14 is made from a conventional Fresnel lens 10, but replaces the conventional curved surface 32 with a stepped approximation thereto 22, 24, 26, preferably of three steps. The thickness of the stepped lens 14, at each step, is a half-wavelength or a multiple half-wavelength of the radar operating frequency in the medium of the lens 14. The half-wavelength or multiple half-wavelength separation of the steps 22, 24, 26 causes reflections from the front 16 and rear 18 surfaces to cancel, thereby minimizing the (undesirable) standing wave between the lens 14 and the feed horn or feed horns 46, 48, 50. This avoids the necessity of reducing the standing wave by presenting the curved or stepped side 18 forward. The planar side 16 of the lens 14 (unlike the stepped side 18) doesn't need to be protected from road debris. The lens 14 can therefore be molded as an integral unit of a radome, desirable in the automotive setting. This lens 14 is also thin enough (and, therefore, light enough) that it can be moved side-to-side very rapidly, preferably by a combination of cams 42, 52 and springs 44, 54. This allows a very fast scan, albeit over a limited field of view. Gimballing 56 the lens 14 and feed horns 46, 48, 50 together provides a slower scan, but gives an unlimited field of regard. Combining the two gives a fast scan and unlimited field of regard, desirable in the missile setting. <IMAGE></p> |
