Abstract: A unidirectional transducer for a surface acoustic wave (SAW) device. In one embodiment the device includes (1) a defined area on a piezoelectric substrate within which is located an open circuit reflector perpendicular to the SAW direction of propagation; and a pair of low reflectivity transducer electrodes located within the defined area and connected to opposing bus bars, the electrodes perpendicular to the direction of the SAW propagation and positioned with the excitation center of the pair of electrodes located about seven-eighths of a Rayleigh wavelength at a center frequency of the SAW from the reflector.

Abstract: The invention provides a method of manufacturing piezoelectric wafers of surface acoustic wave (SAW) identification tags. In one embodiment, the method includes: (1) using a master reticle to form, on each of the piezoelectric wafers, wafer-independent patterns that encode digits of a first significance for SAW identification tags; and (2) using different ones of a library of coding reticles to form, on each of the piezoelectric wafers, wafer-dependent patterns that encode digits of a second significance for SAW identification tags.

Abstract: Embodiments of the invention provide a tamper indicating system using surface acoustical wave tag devices. This is achieved by the use of at least two surface acoustical wave tag devices. In one embodiment, a first surface acoustical wave tag device returns an identification signal in response to an interrogation and a second surface acoustical wave tag devices returns an indication of tampering in response to an interrogation. An antenna assembly is provided comprising conducting elements each of which are deformed to form a partial helix.

Abstract: The present invention provides a system for avoiding code collisions from multiple SAW identification tags and a method of operating such system. In one embodiment the invention provides for (1) focusing an interrogation pulse to within a defined space; and (2) discriminating between coded responses returned from tags located within such defined space.

Abstract: A surface acoustic wave (SAW) identification tag and methods of operating and manufacturing the tag. In one embodiment, the tag includes: (1) a piezoelectric substrate having a SAW transducer located thereon, (2) a group of slots arranged by both pulse position and phase position on said substrate; and (3) a number of reflectors distributed among the slots such that the reflectors encode a number by both pulse position and phase position.

Abstract: A unidirectional transducer for a surface acoustic wave (SAW) device. In one embodiment the device includes (1) a defined area on a piezoelectric substrate within which is located an open circuit reflector perpendicular to the SAW direction of propagation; and a pair of low reflectivity transducer electrodes located within the defined area and connected to opposing bus bars, the electrodes perpendicular to the direction of the SAW propagation and positioned with the excitation center of the pair of electrodes located about seven-eighths of a Rayleigh wavelength at a center frequency of the SAW from the reflector.

Abstract: Surface acoustic wave (SAW) identification tag discrimination methods including, in one embodiment (1) detecting a signal emanating from an electronic device operating within a SAW tag frequency band; (2) identifying a null period in a transmission pattern in the signal; and (3) effecting communication of information during the null period.

Abstract: A method of accommodating code collisions from multiple SAW identification tag coded response pulses. In one embodiment, the method includes: (1) separating probable candidates by time-domain; (2) classifying the probable candidates by code-division separation; (3) employing known coded identification signals to adjust the probable candidates; and (4) correlating the multiple SAW identification tag coded response pulses to identify the probable candidates for further processing.