(12) United States Patent ao) Patent No.: us 6,707,376 Bi
Patterson et al. (45) Date of Patent: Mar. 16,2004
A method to power a radio frequency identification (RFID) reader to increase multi-tag reading capability and increase the reading range of a passive tag without maximizing the continuous transmitted power level is provided. The RFID reader transmits a pulsed interrogation signal until an RFID tag response is received, and then switches to a continuous and pulsed power scheme. The continuous power emitted maintains the power supplied to the RFID tags so the tags will not reset due to loss of power. The pulsed signal permits reading the tags at longer ranges, especially when there is a plurality of tags in the area.
6 Claims, 4 Drawing Sheets