Patent Application
20070001851
This invention relates to Radio Frequency Identification (RFID) systems.
According to some aspects, this invention provides a calibrated simulator RFID tag system or so-called “Golden Tag System”. The invention allows for the evaluation of various emerging RFID protocols. Such a system allows abstraction from the variability of an RF environment, as well as tag-to-tag variation in the case of single chip tags, in order to allow for the objective evaluation of an RFID protocol, or a candidate reader implementation of an RFID protocol, in the presence of a physical communication channel. Such a system, according to embodiments of the present invention, may be used, e.g., to establish benchmarks for vendor implementations of different protocol standards. The Golden Tag Systems according to the present invention allow measurement of RFID systems (referred to herein as system(s) under test) to determine if the systems under test are compatible with a given protocol specification, and/or to extract performance measurements from the system under test.
A Golden Tag System according to embodiments of the present invention enables:
The invention is better understood by reading the following detailed description with reference to the accompanying drawings in which:
As used herein, the following terms have the following meanings. These terms are defined here to be used in describing exemplary embodiments, and are not meant to limit the scope of the invention in any way:
EPC refers to an Electronic Product Code which provides a numbering standard.
FPGA means a Field Programmable Gate Array which is generally an array of logic gates that can be hardware-programmed to fulfill user-specified tasks.
SMA refers to Sub-Miniature version A connectors for radio-frequency circuits.
UHF means ultrahigh frequency and generally refers to a range of the radio spectrum in the band extending from 300 MHz to 3 GHz.
A Golden Tag
A tag unit 10 also includes a detector 14 and a modulator 16, each connected to the FPGA/microcontroller 12. An RF I/O port/connector 18 (such as an SMA connector) provides for external RF connection of the tag unit 10. In addition, the tag unit 10 may interconnect with other tag units via bus 20. The bus 20 may be, e.g., an RS-485 bus, and preferably the connection to the bus is via an RS-485 port. The bus 20 may also be used to supply power to modules of the tag unit. The bus 20 may also provide external signals to the tag unit, such as a reset signal to restart the tag simulator, if necessary.
The FPGA/microcontroller 12 connects to the bus 20 through a level converter 22 which functions to interface the FPGA and/or microcontroller's logic levels to the bus 20's logic levels. This may also include optical isolation or other means of preventing radio frequency interference between the tag unit 10 and other such units or the attached computer.
A power supply unit (PSU) 28 connects to the bus 20 to extract power to operate tag unit 10 from the bus power, if desired.
The detector 14 connects to the RF I/O port 18 via a two-way power splitter 24 and an attenuator 26. The modulator 16 also connects to the RF I/O port 18 via the two-way power splitter 24 and the attenuator 26. In presently preferred embodiments, the attenuator 26 is a 40 dB attenuator. In some embodiments, the attenuator 26 may be a variable/adjustable attenuator, so as to allow for the simulation of various read ranges and signal strengths The I/O port 18 is connectable to the RF ports of an RFID reader or some other device (not shown in figure).
In operation, a read signal (from a reader—not shown) is received via the RF I/O port 18. The detector 14 provides the power level of the received read signal to the FPGA/microcontroller 12, preferably as an analog signal. Additionally, the detector 14 provides information from the reader (reader-to-tag information, shown in the drawing as R->T bits) to the FPGA/microcontroller 12. In response, and based at least in part on the signals received from the detector 14, the FPGA/microcontroller 12 may return an EPC code (or some identifier) stored therein.
If the FPGA/microcontroller 12 does respond to a read signal, the value it provides (shown in the drawing as T->R bits) is modulated (by modulator 16) and sent to the RF I/O port 18 for transmission to an RFID reader (not shown) connected thereto.
A Tag Population
A tag population simulator is made up of a collection or bank of tag units/simulators such as those described above with reference to
Each tag unit 10-k in a tag population simulator 30 is connected (via its respective RF I/O port) to a variable/programmable delay/attenuator mechanism 32-k. Thus, as shown in
A golden tag population simulator according to embodiments of the present invention provides/supports some or all of the following features:
In some embodiments, the tag units may be implemented on two inch by three inch PCBs with a stacking bus connector, allowing a varying number of tag units to be interconnected to a backplane module which is in turn connected to a PC via a serial port interface.
Simulator Software
The computer 32 connected to the golden tag population runs simulator software 33 which implements/supports at least some of the following features:
In operation, a tag population simulator according to embodiments of the present invention provides a calibrated simulation of a large population of tags, e.g., for the purpose of measuring EPC reader performance.
The simulator software is not limited to the above-mentioned functionality, and one skilled in the art will realize that additional and/or different functions may be provided by the simulator software. Furthermore, the simulator software may by customized for specific protocols.
In some embodiments, some or all of the simulator software's functionality may be provided via a command line interface (CLI). In this manner, the test commands may be used as part of a script which executes a suite of tests in sequence, making manufacturing tests, acceptance tests, and performance benchmarking of new reader devices as simple as possible. In addition to the command line interface, some embodiments may provide a graphical user interface that would provide intuitive access to the test modes for bench testing.
In some presently preferred embodiments, the tag units in a population include EPC Class 1 UHF simulator tags and/or EPC Class 1, EPC Class 1 Generation 2, and Class 0 UHF simulator tags and/or EPC HF simulator tags. The EPC Class 1 UHF simulator tags are preferably capable of running the full Auto-ID UHF EPC Class 1 protocol, including Class 1 Generation 2 support, and each such tag is microprocessor-based and includes an RS232 Port, an RS485 Port, a basic API, an antenna Port and calibrated RF performance. The EPC Class 1 and Class 0 UHF simulator tags are capable of running the full UHF EPC Class 1 and EPC Class 0 protocols, and the EPC HF simulator tags are capable of running the HF EPC protocol.
In some presently preferred embodiments, the population simulator boards are capable of connecting up to 30 HF or UHF tags (including mixed populations). Some embodiments of the present invention provide the ability to connect multiple boards to the host PC.
Golden Tag Simulation and Test System
A test application running on the computer 44 executes some or all of the following tests by interacting with the reader under test (RUT) via the Ethernet network. (Most of the interaction consists of configuration tasks, reader queries and performance benchmarking):
The computer test application may set up the tags in various configurations in order to enable certain tests, and may read certain measurements from the tags after completion of the tests. To avoid unpredictable interactions between the test software and the reader under test, the computer application preferably only interacts with the tags before and after an experiment. The PC application may provide some or all of the following functionality relative to the tags simulators (Golden tags):
While one skilled in the art will realize that any number of hardware configurations are possible using the simulator tags and tag population simulators of the present invention, a presently preferred hardware configuration includes the following:
The present invention thus provides, in some aspects, so-called “golden” RFID tags and related systems and methods. There is an acute need for such systems, e.g., when developing, testing, and benchmarking RFID readers. They are also valuable tools for tag protocol development, since each tag population board may contain a microcontroller or FPGA implementation of the protocol being developed.
While some aspects of the invention have been described as being implemented in hardware or software, one skilled in the art will realize that certain elements may be implemented in hardware, software or combinations thereof.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
