Importance

Loading Importance Indicators...

Abstract

An identification system is provided for identifying a plurality of randomly aligned object-based transponders (18, 20, 22) passing through a predetermined reading volume. A reader (10) includes multiple transmitting and receiving antenna arrays (12, 14, 16) which are arranged sequentially to transmit interrogating and energizing fields (29) into the reading volume, with each energizing field having a different polarisation. Each transponder (12, 14, 16) is arranged to be powered by at least one of the interrogating and energizing fields, and includes a short term memory module (30) which is arranged to record the successful transmission or otherwise of the identification signal of the transponder (20) and to retain the record in the absence of a power supply to the transponder. The short term memory module has a retention time longer than any predicted interruption of power supply to the transponder via one of the energizing fields within the reading volume. The minimum memory retention time is typically the time period taken for the sequential transmission of all but one of the interrogating and energizing fields (29) during an interrogation cycle.

Loading the Abstract Image...

First Claim