High Frequency RFID Reader ICs Propel New Application Designs
By ShreHarsha Rao, Texas Instruments
According to Moore’s Law, the number of transistors on an IC (integrated circuit) doubles every 2 years. In theory then, the performance and functionality of ICs
Figure 1. Texas Instruments TRF7960 Reader IC Module. |
will continue to increase exponentially. It’s this continual improvement that has created a new generation of reader ICs. These advanced ICs allow for an innovative approach to RF design, and are enabling a host of new radio frequency identification (RFID) applications.
Previous versions of reader ICs presented quite a few challenges for engineers looking to integrate the chips into their designs. One of the main barriers was that reader ICs, specifically 13.56 MHz high-frequency (HF) chips, were unable to be fully integrated into RFID solutions. Multiple ISO/ IEC standards that target different applications presented a challenge because no readers could address all protocols. To create a workable solution, designers needed to include a second chip that could support the additional ISO/ IEC standards. The size of previous reader ICs was another factor limiting its integration and use in new applications; the larger the chip size the more difficult to integrate. With larger chips, the trade off of what a product would gain from embedded RFID compared with the space the chip would occupy proved not worth the price in many applications.
Earlier Reader Chips
The two final prohibitive characteristics of earlier reader chips were their cost and performance. Incorporating RFID into products with previous reader ICs designs could greatly increase each system’s bill of materials (BOM). In addition to being more expensive, the performance of earlier reader chips was not ideal. The ICs operated using a single receiver input architecture, amplitude modulation (AM). Due to interference from other tags in the field and/or different tag orientation, the amplitude modulated data coming from the tag can undergo an AM-PM conversion to yield a Phase Modulated signal. If the RFID reader has only an AM receiver, this Phase Modulated (PM) signal is not detected and there may be a possibility of a read-hole. And because previous reader ICs were large and only operated in one power mode, battery life was limited.
The next generation of reader ICs, like the Texas Instruments TRF7960, address the limitations of earlier chips and, in doing so, simplifies circuit design and opens up more potential markets and applications for integrating RFID into devices. New reader ICs have fully- integrated protocol handling and support multiple ISO standards including ISO/ IEC 15693 and ISO/ IEC 14443A/B, making them more flexible. And because they don’t require a second chip, these reader ICs are more easily and inexpensively incorporated into devices. Additionally, the chips are significantly smaller, measuring just 5 mm × 5mm (compared with previous chips that were 20 mm × 20 mm or larger). Prior versions of reader ICs used two 13.56 MHz crystals, one for the reader and the one for the microcontroller, but new chips provide clock output to the microcontroller removing the need for a second crystal. Using just one crystal not only reduces the BOM, but also the size of the module. The entire reader sub-system (IC, micro controller, and crystal) is smaller than previous reader ICs alone. This difference in size is especially important when designing RFID into smaller products. For example, if developing an RFID-enabled blood glucose meter. The meter’s small size is an important selling proposition, and few companies would be willing to create a larger glucose meter just to accommodate an RFID function.
New Reader ICs Provide Improved Performance
Despite the reduction in size, new reader ICs actually outperform previous chips in three main areas by providing greater read range, longer battery life and fewer read holes. By integrating low drop out regulators (LDOs) with high power supply rejection ratios (PSRRs), the new ICs deliver increased read range for the same amount of power as current chips. Separate internal power supplies for analog, digital and power amplifier (PA) sections eliminate noise coupling and improve tag read reliability. And the adjustable voltage 20 mA LDO output for powering the external microcontroller eliminates the use of an external regulator, reducing module cost and minimizing board space.
The new chip’s dual input receivers assure better coverage between RFID tags and readers by eliminating the read holes which occur when an RFID tag’s antenna changes the tag return signal from AM (amplitude modulation) to PM (phase modulation). The dual AM and PM receivers, coupled with the receive signal strength indictor (RSSI), ensures that the strongest signal is decoded. This translates into high reliability and makes the solution ideal for an application such as ski and transit ticketing where read holes can occur due to variability in tag orientation with respect to the reader. New reader ICs are also more power efficient and allow manufacturers to select power modes to maximize battery life. The chips contain seven user-selectable power modes, ranging from 120 mA in active and full power mode (Pout=200m W) to <1 µA in complete power down, to maximize battery life.
Industries that Stand to Benefit
In addition to the few applications already mentioned, blood glucose monitoring and transit ticketing, there are four main industries that stand to benefit greatly from new reader IC technology. The first being the access control market.
For RFID-enabled employee identification cards, corporate entrance and exit systems, and other access control applications, size, power and flexibility of the reader are important. Readers need to be small, especially if they’re handheld devices, powerful enough to read tags quickly on the first tap and flexible enough to operate with multiple ISO/ IEC standards.
The second major industry that will benefit from advancements in reader ICs is the financial market, particularly at the point-of-sale (POS). To date there have been approximately 45 million contactless payment cards issued in the U.S., retailers from McDonald’s to CVS have implemented contactless payment, and use of contactless cards abroad continues to grow. One of the major barriers to growth in this market, however, are the varying standards of each country; the U.S. and Europe predominantly use ISO/ IEC 14443 Type A & B, Japan uses FeliCa™, and the list goes on. The new reader ICs can accommodate standards across the globe, making payment terminals that can be used universally.
The third industry that was previously touched on is healthcare. Cost and size are the two main considerations when implementing RFID into medical products. With recent developments in reader IC technology, it’s possible to integrate RFID into these devices without sacrificing the size and drastically increasing the cost. Austin-based Motion Computing recently integrated RFID into its Motion C5 mobile clinical assistant using Texas Instrument’s TRF7960 high-frequency, multi-standard RFID reader IC family. The chip’s small size and low power consumption helped to enable Motion Computing’s development of a thin, lightweight (about 3.3 pounds) portable computer that’s being used by physicians and nurses in hospitals around the U.S. to track and update patient records. The device ensures that the right patient receives the right dose of medication at the right time.
The final area that will benefit from advanced reader ICs is authentication. Electronic documents (such as epassports), high-value asset tracking, and pharmaceutical authentication require an RFID solution that is reliable and accurate. The elimination of read holes, standards compatibility and the speed of new reader ICs make them ideal for authentication applications where literally hundreds of items need to be read or updated quickly and accurately on-the-fly.
Conclusion
Staying true to Moore’s Law, ICs continue to get smaller while performance gets better and Texas Instruments TRF796x family of new HF reader ICs are no exception. With their high integration, smaller size, reduced bill of materials, greater read range, longer battery life and fewer read holes, new reader ICs are making it increasingly less difficult and more beneficial for engineers to design RF-enabled products.
About the Author
ShreHarsha Rao is a RF systems and applications engineer for TI’s Business Development.
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