| 摘要 |
<p>A focussing apparatus essentially comprises a truncated outer cone and a coaxial inner cone which between them define a narrow annular passageway through which signals can be transmitted from and to a transducer. The arrangement tends to create a substantially parallel beam of radiation and the focussing apparatus has very good directional characteristics. The transducer is mounted on a pillar within a transducer housing collar resulting in a very compact design. The inner cone is held in place by a number of radiating ribs so that the apex of the cone lies on the plane of truncation of the truncated cone.</p> |
