1. Field of Invention
The present invention relates to a radio frequency identification (RFID) reader using a plurality of antennas for reading data from Tags, and more particularly to a RFID reader using a plurality of antennas applied to multi-dimensional objects, such as three-dimensional jigsaw with multimedia sound and light effect, to distinguish the orientation of the three-dimensional jigsaw unit between right and wrong.
2. Description of Related Arts
Radio Frequency Identification (RFID) systems are used for identification and/or tracking of equipment, inventory, or living things. RFID systems are radio communication systems that communicate between a radio transceiver, called a RFID reader, and a number of inexpensive devices called Tags or transponders. In RFID systems, the RFID reader communicates to the Tags using modulated radio signals, and the Tags respond with modulated radio signals. Conventional RFID systems are designed a) to identify an object passing into range of the RFID reader, and b) to store data onto the Tag and then retrieve that data from the Tag at a later time in order to manage inventory or perform some other useful application. In this application, the transmit and receive antennas have the same bandwidth. In fact, transmit and receive frequently share the same antenna, using a circulator to separate the transmit and receive paths.
As described in the U.S. patent application Ser. No. 11/062,815, filed on Feb. 23, 2005, a radio frequency identification (RFID) reader comprising a plurality of antennas could be applied to multi-dimensional objects, such as three-dimensional jigsaw with multimedia sound and light effect, Monopoly board game, . . . etc. However, in this prior art each of antennas in the RFID reader is positioned in a central region of each plane of multi-dimensional objects such as three-dimensional jigsaw. In order for the RFID reader to sense the identifier, the polarizations of the electromagnetic fields generated by the antennas in the RFID reader and Tag must be aligned. In most real-world implementations, however, the orientation of the Tag, and, hence, the polarization of the field generated by the Tag's antenna, is unknown. Therefore, the RFID reader could not distinguish the orientation of the three-dimensional jigsaw unit between right and wrong because the modulated radio signals are non-direction signals. In other words, the RFID reader could not distinguish the orientation of the three-dimensional jigsaw unit between right and wrong even though the three-dimensional jigsaw unit aims at the right position. Therefore, there is a need in the art for a RFID reader that can read Tags and also distinguish the Tags' orientations.