Abstract: A method of identifying articles, each of which has a data carrier that includes identifying data of the article, the data carriers having an operation frequency, provides a robust electromagnetic (EM) field within an enclosure in which the articles are stored, even when the natural resonance frequency of the enclosure differs from the operation frequency of the data carriers. In one case data carriers comprise, RFID tags. The EM energy at the operation frequency that is injected into the enclosure to form the robust EM field is injected at a selected location in the enclosure so that the reflected phase of the EM energy from enclosure walls equals the location of injection thereby producing a robust EM field to activate and/or detect data carriers. Active impedance matching is also provided.

Abstract: An automatic data collection system tracks articles by providing a robust electromagnetic (EM) field within an enclosure in which the articles are stored. Respective data carriers, such as RFID tags, attached to each article respond to the electromagnetic field by transmitting unique data identified with each article. Where the frequency of the EM field coupled to the enclosure differs from the natural resonance frequency of the enclosure, the placement of a probe to couple energy to the enclosure is selected to have the reflected phase of the EM energy from walls equal at the probe location thereby producing a robust EM field to activate and/or detect data carriers.