System for minimizing coupling nulls within an electromagnetic field

摘要

A system is disclosed for avoiding and/or minimizing coupling nulls between an electromagnetic field derived from one or more sources and a plurality of randomly oriented RFID tags. The plurality of tags is arranged to move relative to the filed such that no tag is persistently located in a coupling null relative to the field. The or each tag may be translated and/or rotated relative to the electromagnetic field. Alternatively, the electromagnetic field may be translated and/or rotated relative to the tags. In a further aspect coupling nulls may be avoided by orienting a main axis of the or each source of electromagnetic radiation obliquely relative to a direction of movement of the plurality of tags.