By Mark Roberti

June 21, 2004—Companies that manufacture products that are made of—or packaged in—materials that are not "RF friendly" are concerned about how they are going to meet mandates from retailers. It’s difficult to tag many liquid products, because water absorbs electromagnetic radiation at UHF frequencies (868 to 956 MHz). And UHF waves bounce off of metal, making it difficult to read tags on canned goods, items in foil wrapping and other products made of metal or contained in metal packaging.

Gillette puts a tag where there's an air gap in the case

These are not the only materials that cause problems. RF energy is absorbed by containers made with carbon fibers, which are often used in the electronics industry to prevent electrical components from being damaged by electrostatic discharges. RF energy is also absorbed by containers designed to be used in microwave ovens. And frozen foods can be a problem, because the tags often fall off cases with frost on them.

Retailers are requiring tags on cases—which may be in random orientation to a reader antenna—to be read on conveyors traveling at up to 540 feet per minute. This is doable, even with products that are not RF friendly. With smart strategies—good system design, precise tag placement and changes to business processes—it’s possible to tag almost any item so it can be read reliably.

1. Consider tag and reader antenna placement carefully. It's obviously easier to read a tag if you don't have to read through the product that it's on. So wherever possible, it's better to have a reader antenna facing the side of a container, carton or case with the RFID tag on it. Since it's not always possible to control the orientation of an object, it makes sense to set up reader antennas on all sides of a conveyor, door or portal where you want to read tags.