Electro-magnetic ultrasonic wave converter

: Huebschen, G.; Hickethier, M.

Abstract
An electromagnetic ultrasonic wave transducer for exciting transversal waves polarized perpendicular to the plane of incidence, said transversal waves having a unilateral directional characteristic, consists of an arrangement of rows of permanent magnet segments (2, 12, 22, 32) and at least one high-frequency coil (3, 13) which is arranged in segments below the permanent magnet segments. At least four rows of permanent magnet segments (2, 12, 22, 32) are provided, whereby two adjacent rows of magnetic segments (2, 12; 12, 22; 22, 32; 32, 2) are displaced by a quarter of a periodicity of individual permanent magnets (1) of every row (2, 12, 22, 32) along their longitudinal axis. Furthermore, for each of the adjacent permanent magnet arrangements (2, 22 and 12, 32), a separate high-frequency coil (3 or 13) is provided, said high-frequency coils being applied with an ultrasonic signal shifted by 90 degrees between the two high-frequency coils (3, 13). This achieves the situation that the ultrasonic wave transducer has a unilateral directional characteristic both as a transmit transducer as well as a receive transducer with a principal beam direction, so that the result is an improved signal-to-noise ratio during the non-destructive material test.