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How rfid can bring value to the technology creation chain

communications design

The electronics industry has been searching for an auto ID solution that can more than traceability. Ideally, such a technology could become the backbone for product lifecycle management.

Optical identification, including bar codes or data matrices, cannot be used because these carriers can become inaccessible once a pcb has been mounted in its enclosure. Similarly, rfid developers have yet to create a flexible multipurpose solution, but this situation may be changing.

Initially, rfid using lf and hf frequencies was examined. While they seem suitable, these technologies use relatively low frequencies (lf: 125kHz; hf: 13.56MHz) and have correspondingly long wavelengths. This means relatively large antennas are needed to support read distances of more than a few centimetres.

The uhf band therefore offers a better opportunity to implement passive rfid, enabling communication over distances of more than 5m using small antennas. The RFID Value Creators consortium (see box) is looking to make this technology more widely available across the value chain, from the product development process onwards.

The basic element of any rfid system is the tag, which uniquely identifies the product. With the size and complexity of electronic systems, the questions include where is the value of the product located and where should the tag be mounted? The pcb is an obvious candidate because it carries the functionality and marks the beginning of the value creation process. Theoretically, the pcb is also suited for rfid because it features a large metal ground plane, which could be used as an antenna.

This is where Murata's Magicstrap comes into play. This combines a conventional uhf rfid ic (currently UCODE from NXP) with a ceramic multilayer structure carrying an adaptive matching circuit. This integrated component can be placed onto the pcb using standard surface mount technology. Because the matching circuit enables the pcb's ground plane to be used as an antenna, Magicstrap can turn any pcb into a functioning uhf rfid tag and a board area of 0.25cm² is large enough to provide a read range of more than 50cm. For maximum flexibility, four layouts are available, resulting in different read distances for a given pcb size (see fig 1).



Designers should also remember the longest pcb edge is another factor influencing communication distance (see fig 2).



In a manufacturing environment, it is often necessary to address individual pcbs, which raises the problem of unwanted reads. As read distances of several metres are possible with Magicstrap, a reader whose antenna and transmit power are designed for maximum reach will address all tags within its range. This may be an advantage in logistics applications, where it is often necessary to scan many items simultaneously, but could be a drawback where error free identification of individual boards is required for traceability. PCBs are often grouped on panels during manufacture so, it may be necessary to identify the exact PCB to which the components are being mounted.

Kathrein's antenna portfolio, in combination with Brooks' readers and integration experience, help with this problem. In addition to antennas for medium or long range reads, Kathrein also provides the LORA antenna, allowing UHF tags which are very close to each other to be addressed.

Back to the roots
Many companies either have no manufacturing operations or little spare capacity, which has seen demand grow for prototype manufacturing services. Consortium member Beta Layout offers such a service and uses rfid to differentiate between pcbs which may look the same, but differ subtly.

The company's solution uses the fact that, because the matching circuit in Magicstrap's multilayer structure also works as an antenna, it can be used as a complete uhf tag. The only trade off is that read distance will be degraded. However, read distances of several millimetres can be achieved.

Rather than mount Magicstrap as a component, Beta Layout has integrated it into the pcb. Apart from prototype management applications, this approach can also be used to implement a hidden counterfeit protection scheme. Beta Layout can deliver prototype pcbs with integrated rfid functionality if desired, allowing customers to evaluate rfid functionality early in the product creation process.

While this specific use case can be supported using standard reader technology, a loop antenna must be connected to the reader for successful communication with Magicstrap and Beta Layout provides a low cost solution for this. An alternative is to use Kathrein's LORA antenna, which also couples with Magicstrap without the need for a booster antenna.

Another question is how pcbs with a fixed design can be enhanced by rfid functionality. Magicstrap can be used if one of the suggested antennas is added during a redesign. Beta Layout provides an intermediate solution for users who do not have any simulation software or who want to carry out some initial practical tests. The solution consists of mini pcbs which carry one of the three smallest Magicstrap layouts and can be mounted on the existing pcb for initial functional tests.

Last, but not least, Beta Layout offers a complete uhf rfid starter kit designed to meet the needs of development engineers.

The rfid solution described here thus can be used throughout the electronics industry to generate value. Data generated at the early stages by prototype identification will be reliably available during the entire product development phase and beyond.

How useful an rfid solution turns out to be depends largely on the provision of adequate software to process the ID data efficiently. In most cases, an established IT infrastructure will be available and users need only load some middleware to ensure the right data will be routed from the tags to the readers and that the data will then be forwarded to the relevant databases and event monitors.

Physical aspects and an understanding of the process will play an important role. Tags that are not relevant for a particular process will frequently be within the range of a reader used in that process. This problem can also be solved, or at least mitigated, by intelligent software algorithms such as those available from Enso Detego.

Suitable middleware can help to reduce the costs on the way from the first feasibility study to the introduction into current processes. But complete standalone solutions, including server based services, are also available.

Finally, any company implementing such a solution will find the value of RFID extends to end of life and recycling.

RFID Value Creators
Current members of the consortium include:
• Murata, which provides a range of components that use the electrical properties of ceramic materials, including rfid tags and readers;
• NXP Semiconductors, a market leader in rfid technology;
• Brooks Automation, a provider of rfid system solutions for logistics, manufacturing and quality control operations;
• Kathrein, one of the leading developers and manufacturers of antennas,
• Enso Detego, which supplies flexible, hardware independent software modules that allow rapid implementation of rfid projects; and
• Beta Layout, a leading manufacturer and distributor of pcb prototypes.

Alexander Schmoldt is business development manager, Europe, with Murata Electronics.

For more, go to www.rfid-valuecreators.com

Author
Alexander Schmoldt

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