A spectrum analyser and other apparatus for detecting at least one particular frequency component in an electrical signal

摘要

A spectrum analyser for analysing an electrical signal into its different frequency components, first converts the signal into surface acoustic waves. These surface acoustic waves are separated spatially into different frequency components by, for example, using an interference effect (Fig. 1 not shown) or by using a refraction technique Fig. 4. Referring to Fig. 4 the signal to be analysed is applied to a transducer 16A, 16B and 17, which launches surface acoustic waves along a silicon member 15. Different frequency components of the surface acoustic waves are focussed by a dispersive lens 22 onto respective different focal spots 18 and generate voltages in a piezoelectric layer 20. These voltages are rectified by diodes formed integrally in the member 15 to produce rectified D.C. outputs at terminals f1, f2, f3, and f4. IMAGE