The present invention comprises a radio frequency identification device
that utilizes multiple operating frequencies. In one embodiment of the
present invention, one frequency (e.g., an ultra-high frequency such as
915 MHz, 800 MHz, 915 MHz, or microwave frequency such as 2.45 GHz) is
used for data transmission, and another frequency (e.g., a low or high
frequency such as 13.56 MHz) is used for field penetration. In another
embodiment, one frequency is used for reading information received from
the multi-frequency identification device, and another frequency is used
for writing to the multi-frequency identification device. In an
additional embodiment, the multi-frequency identification device utilizes
one antenna for all frequencies. In another embodiment, the
multi-frequency identification device utilizes two or more antennas for
different frequencies, and one common memory. In other embodiments, one
or two digital parts, analog parts, antennas, and memories can be used.