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Design of UHF-based RFID Systems

In order to deploy radio frequency identification to its maximum potential, be sure to consider real-life usage scenarios of a product by an end user, take into account deployment scalability and support, and understand the technology and its limitations.
By Akshay Bal

When designing solutions for UHF or HF reader applications, important aspects to consider include the loss of signal from reader to antenna, the distance of the tag from the antenna and the orientation of the tags to the antennas, which would determine where we should use linear- or circular-polarized antennas. If the antennas are being custom-designed in-house, the impedance matching of the antenna with the cable connecting to the reader needs to ensure maximum power transfer with minimal loss. This will also impact its ability to read multiple tags.

The basic data flow of the solution can be described as tag – antenna – reader – software. The data transfer from the tag to the software is what would determine how efficient the RFID system is in its design. When designing a UHF solution, one very important factor is the workflow in which the RFID hardware would operate. To be specific, the tag's workflow, or its movement throughout the ecosystem in which the application will be used, will determine the actual location of the antennas, readers, motion sensors and so forth.

For example, if we are designing an application in which a tag would be attached to an item that would, in turn, be tracked throughout a building, it is important to understand where we would establish read points in order for the system to read the tags successfully without missing any tags. In addition, placing minimal RFID hardware whenever we design an application is the best way to reduce interference and increase read rates. Therefore, the placement of the antennas, the readers, the GPIO devices and the tags needs to be streamlined and minimal, and understanding the workflow in which the tags will operate is vital.

If the workflow does not work in favor of the application, it is highly recommended to evaluate it and consider this an opportunity to improve it. Be sure to work with the least amount of hardware at the lowest cost, so as to achieve the ROI goals and maximum the system's efficiency. Having large numbers of RFID hardware parts to track items only increases the complexity of the system and leads to errors in reading the tags from the antennas, due to external induced noise. Design problems that are usually seen with passive UHF RFID solutions end up reducing tag readability.

When the application is developed with all of these factors considered, we can expect a good amount of tag flow from the antennas to the reader. The next step in the design would be to transfer this tag data from the readers to a middleware solution, if needed, which would compile the information being collected from the reader into meaningful data that could then be used by the software designed for the RFID application. The software would enable user interaction with this data and perform the required activities needed to complete the business and user needs.

Many RFID applications run into deployment challenges that result from design limitations. For example, the application might be designed with excessive hardware with maximum read points, due to complex workflows—which, in turn, increase the cost of the entire solution. The environment in which the application is deployed may induce RF interference and reduce tag reads.

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