| 摘要 |
A focussing apparatus essentially comprises a truncated outer cone (10) and a coaxial inner cone (11) which between them define a narrow annular passageway through which signals can be transmitted from and to a transducer (30). The arrangement tends to create a substantially parallel beam of radiation and the focussing apparatus has very good directional characteristics. The transducer (30) is mounted on a pillar (32) within a transducer housing collar (12) resulting in a very compact design. The inner cone (11) is held in place by a number of radiating ribs (13) so that the apex of the cone lies on the plane of truncation A-A of the truncated cone (10). |
