| 摘要 |
1,110,938. Elastic wave transmission systems. WESTERN ELECTRIC CO. Inc. 6 Oct., 1965 [6 Oct., 1964], No. 42345/65. Heading H3U. An elastic wave transmission system comprises means for launching an elastic wave for propagation in a given direction along a transmission path, the path including a body of non- conductive ferromagnetic material having gyromagnetic properties for shaping the front of the wave, the body being magnetized with components of magnetization parallel to said given direction that vary in strength with radial distance away from the centre of the transmission path. In a particular application the system functions as a delay line and the magnetic field strength increases with the radial distance to cause the front of the propagated wave to be more delayed at the centre than at the edge whereby the wave front has a convex form so that the transmitted energy is focused towards the receiving end of the transmission path and less energy is lost by interacting with the boundary of the path. The underlying theory is described. An embodiment of a delay line, Fig. 1, comprises a transmission path formed of two cylindrical bodies 10, 10<SP>1</SP> of glass or metal alloy and bonded respectively, to input and output piezoelectric transducers 11, 12. The diverging propagated wave front 19 is focused into a concave wave front 20 by means of a cylindrical body 14 of ferromagnetic material having gyromagnetic properties, e.g. yttrium iron garnet, lithium ferrite, europium iron garnet, this body being bonded to the bodies 10, 10<SP>1</SP>. A solenoid 15 having a short axial length compared with its diameter produces a field having components parallel to the path axis 13, this field increasing in intensity with radial distance away from the axis (Fig. 2, not shown). The field may alternatively be formed by a permanent magnet (Fig. 5, not shown). |
