Medical article tracking with injection probe providing magnetic near field dominance

A method for tracking medical articles stored in the interior volume of a container, the interior volume of the container having a size selected to receive a plurality of medical articles each of which has a wireless identification device associated therewith that has individual identification data, and each wireless identification device configured to respond with identification data upon receiving activation energy, the method comprising:

• shielding the interior volume of the container from the passage of electromagnetic (“EM”) energy from the passage of electromagnetic energy both into and out of the interior volume, whereby the interior volume is isolated to keep activating RF energy within the container so that RFID tags located outside the container are not activated and read;
• injecting activating radio frequency (“RF”) energy into the interior volume in an energy pattern with an injection probe located within the EM shielding to fill the interior volume with an EM field, wherein the injection probe comprises a main conductive element having capacitive coupling across at least one slot of the main conductive element thereby forming an isolated electric field that fills the interior of the container, and wherein the main conductive element is located in relation to a ground plane to thereby form a robust magnetic field that is orthogonal to the electric field and that also fills the interior of the container;
• delivering activating RF energy to the injection probe from a signal source;
• controlling the signal source to deliver the activating energy to the injection probe for injection into the interior volume, and controlling the signal source to stop delivering activating energy to the injection probe, whereby responsive identification signals from activated identification devices located in the interior volume can be received.

A tracking system for medical articles stored in an interior volume of a container, each of the medical articles having a wireless identification device that is configured to respond with respective identification data upon receiving activation energy, the system comprising:

• electromagnetic (“EM”) shielding located about the interior volume of the container to shield the interior volume of the container from the passage of EM energy both into and out of the interior volume, whereby the interior volume is isolated to keep activating radio frequency (“RF”) energy within the container so that wireless identification devices located outside the container are not activated and read;
• an EM energy conducting injection probe located within the EM shielding, the injection probe located and configured to inject activation RF energy into the interior volume having an energy pattern directed to fill the interior volume of the container with an EM field, wherein the injection probe comprises a main conductive element having capacitive coupling thereby forming an isolated electric field that fills the interior volume of the container, and wherein the main conductive element is located in relation to a ground plane to thereby form a robust magnetic field that is orthogonal to the electric field and that also fills the interior volume of the container wherein both fields are circularly polarized;
• a signal source producing activation RF energy and coupled to the injection probe;
• and
• a processor connected with the signal source and with the injection probe, the processor being programmed to control the signal source to deliver the activation RF energy to the injection probe for injecting into the interior volume of the container to activate identification devices in the interior volume, the processor further being programmed to stop the signal source from delivering RF energy to the injection probe to allow identification signals from activated identification devices in the interior volume to be received wherein the processor receives the identification signals from activated identification devices in the interior volume through the injection probe.