Single frequency low power RFID device
Methods, systems, and apparatuses for a reader transceiver circuit are described. The reader transceiver circuit incorporates a frequency generator, such as a surface acoustic wave (SAW) oscillator. A reader incorporating the reader transceiver circuit is configured to read a tag at very close range, including while being in contact with the tag. The transceiver can be coupled to various host devices in a variety of ways, including being located in a RFID reader (e.g., mobile or fixed position), a computing device, a barcode reader, etc. The transceiver can be located in an RFID module that is attachable to a host device, can be configured in the host device, or can be configured to communicate with the host device over a distance. The RFID module may include one or more antennas, such as a first antenna configured to receive a magnetic field component of an electromagnetic wave and a second antenna configured to receive an electric field component of an electromagnetic wave. The RFID module may include a detector that is configured to determine if the RFID module is positioned in proximity to an object, such as a RFID tag. The detector may operate as a trigger for the RFID module, to enable or trigger a function of the RFID module.
1. A radio frequency identification (RFID) system for communicating with RFID tags, comprising:
a host computer; and
an RFID module coupled to the host computer, wherein the RFID module includes
a transceiver,
a protocol processor configured to process RFID tag data,
a host interface connector module configured to communicate RFID tag data with the computer,
a plurality of antennas, and
an antenna selector to couple an antenna of the plurality of antennas to the transceiver.
2. The RFID system of claim 1 , wherein the plurality of antennas includes:
a first antenna configured to receive a magnetic field component of an electromagnetic wave; and
a second antenna configured to receive an electric field component of an electromagnetic wave.
3. The RFID system of claim 2 , wherein the first antenna is a loop antenna.
4. The RFID system of claim 3 , wherein the loop antenna is optimized for ultra high frequency (UHF) frequencies.
5. The RFID system of claim 2 , wherein the second antenna is a dipole antenna.
6. The RFID system of claim 1 , wherein the plurality of antennas includes:
an antenna configured to be more efficient at radiating a communication signal into the near field region than into the far field region.
7. The RFID system of claim 3 , wherein the antenna is a near field E-field coupling antenna, a near field H-field inductive coupling loop antenna, or a lossy transmission line.
8. The RFID system of claim 1 , wherein the RFID module is an accessory attached to the host computer.
9. The RFID system of claim 1 , wherein the host computer forms part of a barcode reader.
10. A data capture system for communicating with RFID tags, comprising:
a host computer; and
an RFID module coupled to the host computer, wherein the RFID module includes
a transceiver,
a protocol processor configured to process RFID tag data,
a host interface connector module configured to exchange tag data with the computer,
an electronically configurable antenna system connected to the transceiver, and
means to configure the antenna system to match properties of an antenna of a RFID tag proximate to the RFID module.
11. The data capture system of claim 10 , wherein the RFID module is an accessory attached to the host computer.
12. The data capture system of claim 10 , wherein the host computer is part of a barcode reader.
13. The data capture system of claim 10 , wherein the electronically configurable antenna system includes:
an antenna configured to be more efficient at radiating a communication signal into the near field region than into the far field region.
14. The data capture system of claim 13 , wherein the antenna is a near field E-field coupling antenna, a near field H-field inductive coupling loop antenna, or a lossy transmission line.
15. The data capture system of claim 10 , wherein the electronically configurable antenna system comprises a plurality of antennas.
16. A radio frequency identification (RFID) reader, comprising:
a transceiver; and
an antenna coupled to the transceiver;
wherein in a first mode, the antenna is tuned to a first frequency;
wherein in a second mode, the antenna is in contact with a RFID tag, wherein in the second mode, the antenna is configured to be tuned for a second frequency different from the first frequency due to a load of the RFID tag in combination with a characteristic impedance of the antenna;
wherein a radiation efficiency of the reader is optimized for the second frequency.
17. The RFID reader of claim 16 , wherein the transceiver utilizes a fixed frequency for a carrier frequency.
18. The RFID reader of claim 16 , wherein the transceiver is configured to perform frequency hopping.
19. The RFID reader of claim 16 , wherein in the first mode, the antenna is configured to radiate a radio frequency (RF) signal having a first energy level, and in the second mode, the antenna is configured to radiate an RF signal having a second energy level, wherein the first energy level is greater than the second energy level.
20. The RFID reader of claim 16 , wherein an equivalent isotropically radiated power (EIRP) level radiated in the first mode is greater than an EIRP level radiated in the second mode.
21. A radio frequency identification (RFID) device for communicating with RFID tags, comprising:
an antenna configured to radiate a RF signal receivable by an RFID tag in a far field region;
a transceiver coupled to the antenna;
a proximity sensor that outputs a proximity signal indicating whether the antenna is proximate to an object; and
a tuning module configured to tune the antenna if the proximity signal indicates that the antenna is proximate to an object.
22. The RFID device of claim 21 , wherein if tuned by the tuning module, the antenna is configured to radiate an E-field radio frequency (RF) signal receivable by a RFID tag in a near field region.
23. The RFID device of claim 21 wherein the antenna is configured to be tuned by contacting the antenna with a RFID tag.
24. The RFID device of claim 21 , wherein an output power radiated by the antenna prior to being tuned is greater than an output power radiated by the antenna when tuned.
25. The RFID device of claim 21 , wherein a power level of an RF signal output by the transceiver to the antenna is reduced if the proximity signal indicates that the antenna is proximate to an object.