| 摘要 |
<p>1005218 Semi-conductor devices WESTERN ELECTRIC CO Inc 18 April 1962 [26 April 1961] 15002/62 Headings H1K H3U UN U22 U30 U34 U29Y U28 and U29B A travelling-wave amplifier for acoustic waves of micro-wave frequency comprises a transmission body 11 of Piezo-electric material, e.g. an X-cut quartz slab, and an electrically biased layer 21 of semi-conductive material, e.g. N or P-type silicon or germanium. The input and output transducers 12, 13 are in the form of electromagnetic coaxial cavities, the ends 25, 26 of the quartz slab being arranged opposite the ends of the inner conductors 15, 16. The slab is shaped to focus the wave into a beam concentrated near the face of the slab to which the semi-conductor layer is attached. Thus, the electric fields associated with the acoustic beam penetrate the layer 21 and interact with the current carriers. A condition for gain is that the ratio of the velocity of the carriers V o to that of the acoustic wave v 1 should exceed unity. Thus, for optimum gain at 1 kmc/s., # o /# s = 1À1 and at 10 kmc/s., # o /# s = 1À5. The velocity of the carriers is proportional to the bias voltage of source 22. The Specification refers to the alternative use of transverse waves in an A.C.-cut quartz bar and to the possibility of using surface (Rayleigh) waves.</p> |
