A null-zone control method for RFID systems

A null-zone control method-which converts a null zone into a readable zone using only the standard antennas of a radio-frequency identification (RFID) reader-was developed. Outdoor evaluation of the method implemented in a RFID tag-reader system demonstrates the validity of the method; namely, it converts the null zone into a readable zone and attains high RFID-tag readability in the near field of the reader antenna.