Home Internet of Things Aerospace Apparel Energy Defense Health Care Logistics Manufacturing Retail

Access This Premium Content

Options To Access This Article:

What Subscribers Are Saying

  • "Probably the best investment I've ever made."
    Steve Meizlish, President & CEO, MeizCorp Services, Inc.
  • "I have found that RFID Journal provides an objective viewpoint of RFID. It you are looking for a resource that provides insights as to the application and implications of deploying RFID, RFID Journal will meet your needs, It gives you a broad perspective of RFID, beyond the retail supply chain."
    Mike O'Shea, Director of Corporate AutoID/RFID Strategies & Technologies, Kimberly-Clark Corp.
  • "No other source provides the consistent value-added insight that Mark Robert and his staff do. In a world dominated by press release after press release, RFID Journal is developing as the one place to go to make the most sense out of the present and future of RFID in commerce."
    Bob Hurley, Project Leader for RFID, Bayer HealthCare's Consumer Care Division
  • "RFID Journal is the one go-to source for information on the latest in RFID technology."
    Bruce Keim, Director, Hewlett-Packard
  • "RFID Journal is the only source I need to keep up to the minute with the happenings in the RFID world."
    Blair Hawley, VP of Supply Chain, Remington Products Company

Solving the Water and Metal Problem

Physics can be used to improve RFID performance on hard-to-tag products.
By Peter Cole and Zhonghao Hu
Feb 01, 2009—It's a well-known fact that conventional electric dipole RFID label antennas will not work when placed against a metal or liquid surface. Some vendors have introduced metal- and water-friendly RFID tags, but they tend to be expensive and bulky or are designed for a particular application. At the Auto-ID Lab at the University of Adelaide in Australia, we have been taking two approaches to develop small and inexpensive RFID label antennas that will perform well on hard-to-read products.

The first approach involves the use of a structure called a decoupler, which separates the tag from the effects of the metal or water surface. We've been working with the Sievenpiper decoupler, originally designed for use in mobile phone antennas to shield users from radiation. We identified incident, reflected and transverse waves that exist in the electromagnetic field just above its surface where the tag should be placed. We established that with correct proportions, the reflected waves can be brought in phase with the incident waves, negating the effects from metal or liquids. Now we're investigating the use of the Sievenpiper decoupler with ultrahigh-frequency RFID labels to determine what performance levels can be achieved.

Left to right: Peter Cole, Zhonghao Hu
At the same time, we're researching the effectiveness of the slotted microstrip decoupler, which has a different shape and properties. It involves the use of a simple, very thin (around 1 mm) insulating slab, with appropriately shaped metal plates above and below, that separates the tag from the effects of the metal or water surface. It's a low-cost solution, especially when the decoupler is manufactured with printed electronics using metallic inks.

Another aspect of our research is focused on fractal antennas, designed for tagging small objects. Fractal antennas are based on intricate, repeating geometric shapes. Their smaller size makes them less expensive to manufacture than dipole antennas. Unlike dipole antennas, which generally have length but not much width, fractal antennas attempt to make good use of space in two dimensions. Our investigation is concentrated on the behavior of radiation and loss resistances. In particular, we are examining how these parameters vary with size, and how well the values can be made to match to the resistance and reactance parameters of RFID chip circuits, and at what efficiency.

Results so far suggest that good efficiency can be obtained with a significant reduction in size, and that an appropriate combination of resistance and reactance for matching to common chip circuits can be obtained. Our research also explores how fractal antennas will perform near metals and liquids, with and without a decoupler. Stay tuned.

Peter Cole is the research director of the Auto-ID Lab at the University of Adelaide in Australia. Zhonghao Hu is a research associate at the lab and a postgraduate student in the university's School of Electrical and Electronic Engineering.
To continue reading this article, please log in or choose a purchase option.

Option 1: Become a Premium Member.

One-year subscription, unlimited access to Premium Content: $189

Gain access to all of our premium content and receive 10% off RFID Reports and RFID Events!

Option 2: Purchase access to this specific article.

This article contains 470 words and 1 page. Purchase Price: $19.99

Upgrade now, and you'll get immediate access to:

  • Case Studies

    Our in-dept case-study articles show you, step by step, how early adopters assessed the business case for an application, piloted it and rolled out the technology.

    Free Sample: How Cognizant Cut Costs by Deploying RFID to Track IT Assets

  • Best Practices

    The best way to avoid pitfalls is to know what best practices early adopters have already established. Our best practices have helped hundreds of companies do just that.

  • How-To Articles

    Don’t waste time trying to figure out how to RFID-enable a forklift, or deciding whether to use fixed or mobile readers. Our how-to articles provide practical advice and reliable answers to many implementation questions.

  • Features

    These informative articles focus on adoption issues, standards and other important trends in the RFID industry.

    Free Sample: Europe Is Rolling Out RFID

  • Magazine Articles

    All RFID Journal Premium Subscribers receive our bimonthly RFID Journal print magazine at no extra cost, and also have access to the complete online archive of magazine articles from past years.

Become a member today!

RFID Journal LIVE! RFID in Health Care LIVE! LatAm LIVE! Brasil LIVE! Europe RFID Connect Virtual Events RFID Journal Awards Webinars Presentations