Surface-wave filter reflection cancellation
Abstract
Abstract UNDESIRED TIME-DELAYED AND REDUCED-AMPLITUDE OUPUT SIGNAL COMPONENTS, DUE TO REFLECTED SURFACE WAVES ARRIVING AT THE OUTPUT TRANSDUCER OF AN ACOUSTO-ELECTRIC SURFACE-WAVE FILTER, ARE SUBSTANTIALLY INHIBITED OR ESSENTIALLY CANCELLED BY CONNECTING TWO OR MORE ACOUSTO-ELECTRIC SURFACE-WAVES FILTERS IN SERIES. FOR THE CASE OF TWO FILTERS IN SERIES, DIFFERENT EFFECTIVE INTERTRANSDUCER SPACINGS ARE EMPLOYED SO THAT THE SECOND FILTER PRODUCES COMPENSATING REFLECTED SIGNAL COMPONENTS WHICH ARE EQUAL IN MAGNITUDE BUT COUNTERPHASED WITH THE REFLECTED SIGNAL COMPONENTS PRODUCED IN THE FIRST FILTER. THESE SECOND-FILTER-REFLECTED COMPONENTS EFFECTIVELY CANCEL THE FIRST-FILTER COMPONENTS WHEN THE TWO ARE COMBINED IN THE SECOND FILTER, RESULTING IN AN OUTPUT SIGNAL WHICH IS RELATIVELY FREE FROM ANY SPURIOUS COMPONENTS DUE TO REFLECTED SURFACE WAVES IN THE FILTER SYSTEM. THE REQUIRED DIFFERENT EFFECTIVE SPACINGS ARE PROVIDED EITHER BY USING DIFFERENT ACTUAL SPACINGS OR BY PROVIDING FOR DIFFERENT ACCUSTIC WAVE PROPAGATION VELOCITIES IN THE DIFFERENT STAGES. SIMILAR COMPENSATION MAY BE OBTAINED IN A SYSTEM CONSISTING OF THREE OR MORE FILTERS.
Inventors
- 👤 Adrian J Devries
Bibliographic Details
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