| 20110210824 | SIGNAL CANCELLING TRANSMIT/RECEIVE MULTI-LOOP ANTENNA FOR A RADIO FREQUENCY IDENTIFICATION READER - In an inductively coupled radio frequency identification (RFID) system deployed in animal and livestock applications, reading system efficacy can be compromised by animal movement on, around, or near metal structures prone to producing sonic frequencies. Such is the case, for example, when a walk-by antenna is mounted at the entry door of a livestock transport trader, and animals transit on a metallic ramp and metallic trader floor. Associated with the observable acoustic noise are subtle disturbances in the magnetic field surrounding the antenna due to vibrating metal altering the reluctance of the antenna's magnetic field. This acoustic noise manifests itself as an electrical noise phenomenon that interferes with the signals of certain types of identification tags which rely on amplitude modulation. The detrimental effects of acoustic noise from metal structures can be mitigated by using a multi-loop antenna that limits the spatial distribution of the transmitted magnetic field and cancels close by magnetic field disturbances. | 09-01-2011 |
