Surface acoustic wave passive transponder having amplitude and phase-modifying surface pads
First Claim
1. In a passive transponder adapted for use in an interrogation system for transmitting a reply signal containing coded information in response to the receipt of an interrogating signal, said transponder comprising:
- (a) a substrate having a substrate surface defining a plurality of paths of travel for surface acoustic waves, each path of travel having a different length from its beginning to its end; and
(b) electric circuit means, disposed on said substrate, for propagating surface acoustic waves along said paths of travel, from said beginning of each path to said end thereof;
the improvement comprising a plurality of selectively removable surface acoustic wave delay pads of prescribed width disposed on the surface of said substrate at prescribed locations along a plurality of said paths of travel to increase the surface acoustic wave propagation time by prescribed increments from said beginning of each of said plurality of paths to said end thereof, the number of said pads in each travel path determining said increase in acoustic wave propagation time along that path,whereby the number of said pads in each travel path may be selected to impart said coded information to said reply signal.
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Accused Products
Abstract
A passive transponder for use in an interrogation/transponder system comprises a substrate having a substrate surface defining a path of travel for surface acoustic waves; a launch transducer element arranged on the surface for converting interrogating signals into surface acoustic waves which propagate along the path of travel; a plurality of tap transducer elements arranged on the surface at spaced intervals along the path of travel for converting surface acoustic waves into respective output signals; and a circuit, connected to the tap transducer elements, for combining the output signals of these transducer elements to form reply signals. In order to control the delay time from transducer element to transducer element, one or more "delay pads" are provided on the substrate surface between these transducer elements.
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Citations
10 Claims
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1. In a passive transponder adapted for use in an interrogation system for transmitting a reply signal containing coded information in response to the receipt of an interrogating signal, said transponder comprising:
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(a) a substrate having a substrate surface defining a plurality of paths of travel for surface acoustic waves, each path of travel having a different length from its beginning to its end; and (b) electric circuit means, disposed on said substrate, for propagating surface acoustic waves along said paths of travel, from said beginning of each path to said end thereof; the improvement comprising a plurality of selectively removable surface acoustic wave delay pads of prescribed width disposed on the surface of said substrate at prescribed locations along a plurality of said paths of travel to increase the surface acoustic wave propagation time by prescribed increments from said beginning of each of said plurality of paths to said end thereof, the number of said pads in each travel path determining said increase in acoustic wave propagation time along that path, whereby the number of said pads in each travel path may be selected to impart said coded information to said reply signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification