Detection of multiple articles

US5519381A · kind A · utility

Assignee

• British Technology Group Limited · GB

Inventors

• Michael J. C. Marsh · Johannesburg, ZA
• Andrzej Lenarcik · Johannesburg, ZA
• Clinton Aiden Van Zyl · Pretoria, ZA
• Andries Christoffel Van Schalkwyk · Pretoria, ZA
• Marthinus Jacobus Rudolph Oosthuizen · Pretoria, ZA

Key dates

• Filing date: Nov 18, 1993
• Grant date: May 21, 1996
• Expiry date: Nov 18, 2013

Classification

• Technology area (CPC G): Physics
• CPC primary: G01S13/87
• WIPO field: Control
• WIPO sector: Instruments

Abstract

An identification system comprises an interrogator and a plurality of transponders. The interrogator includes a transmitter which transmits at least two independent interrogation signals to the transponders, and a receiver for receiving response signals from the transponders. The interrogator also includes processor means for identifying the transponders from data in the received response signals. Each transponder comprises receiving means, a code generator, and transmitter means connected to the code generator. On receipt of at least one of the transmitted interrogation signals the transponder transmits a response signal containing data which identifies it. The interrogation signals may be transmitted continuously or intermittently. In a preferred embodiment, the interrogation signals are relatively narrow bandwidth signals at different frequencies. The receiving means of each transponder has a relatively broad reception bandwidth so that the transponder is responsive to one or more of the interrogation signals.