Closed enclosure with probe for identifying contents of enclosure
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 data identified with each article. An RFID scanner receives the transmitted RFID tag identification data and a processor compares the received identification data to a data base. The data base associates the identification data with data concerning the medical article to which the RFID tag is affixed, such as the name of the medicine, the size of the dose, and the expiration date. The processor is also programmed to keep track of the number of articles of a particular type remaining in the enclosure, to note receipt of an article in the enclosure, and to note removal of the article.
1. A system for reading a data carrier that is attached to an article, the data carrier being responsive to electromagnetic (EM) energy of a frequency f 1 in response to which the data carrier provides unique identification data, the system comprising:
an electrically-conductive enclosure having electrically conductive walls, the enclosure having a natural frequency of resonance f 2 wherein the frequency f 1 is different from the natural frequency of resonance of the enclosure f 2 and wherein the enclosure is configured to be large enough to hold the article to which the data carrier is attached; and
a probe mounted at one of the walls of the enclosure, the probe configured to inject EM energy into the enclosure, the position of the probe being selected so that reflected phase of EM from the walls is equal and in phase at the probe position wherein the position of the probe in relation to the walls of the enclosure is selected to optimize power transfer into the enclosure.
2. The system of claim 1 further comprising an impedance matching circuit configured to more closely match impedance of the probe to impedance of the enclosure.
3. The system of claim 2 wherein the impedance matching circuit comprises an active impedance matching circuit.
4. The system of claim 1 further comprising a drawer adapted to move into and out of the enclosure.
5. The system of claim 4 wherein a portion of the drawer forms a portion of the electrically-conductive enclosure when the drawer is in a predetermined position in relation to the enclosure.
6. The system of claim 5 wherein the drawer is non-electrically conductive except for a portion of the drawer that forms the portion of the electrically-conductive enclosure.
7. The system of claim 5 wherein the drawer is slidable into and out of the enclosure through an opening in the enclosure, the drawer having a front panel that is electrically conductive and that contacts the electrically-conductive enclosure when the drawer is slid to a predetermined position within the enclosure.
8. The system of claim 1 wherein the walls of the enclosure are metallic.
9. The system of claim 1 wherein the walls of the enclosure form a Faraday cage.