UHF RFID's Key Constraints

By Vinod Kankaria

May 8, 2006—Before deploying a UHF passive RFID solution, there are a number of critical parameters to consider. Listed below are a dozen essential ones to bear in mind.

1. Make sure the materials being tracked at a particular portal are of similar type. For example, cartons, trolleys, pallets, glass materials, documents and metal or plastic bins cannot be tracked simultaneously using a single portal. Since the RF energy level backscattered (reflected) by passive tags placed on different materials varies greatly, it is virtually impossible to have a single reader power level give a 100 percent read rate for all materials.


2. Make sure the tagged materials or objects travel in a defined pattern, and that they are not being moved by multiple modes of transport such as forklift, people and metal or plastic trolleys. There needs to be just one transportation mode—or perhaps two, at most—well tested for a 100 percent read rate.

3. When using tags based on different standards—EPC Gen 1 and EPC Gen 2, ISO or other vendor-based tags, for instance—make sure to test all of them, as performance can differ significantly. You’ll find it difficult to configure the reader power level at such an optimum level that it supports all types of tags with a 100 percent read rate. Ideally, try to use a single standard and single vendor in one portal.

4. Orientation is one of the biggest factors for providing good read rates, even if you are using dual dipole tags, which perform better in all orientations.

5. Different tag sizes, shapes and encapsulation provide varying RF energy levels. Hence, I recommend utilizing a single size and shape unless it is not possible to do so. Define a proper document on the encapsulation standards and materials used, so that the same specifications can be followed whenever more tags need to be manufactured.

6. The positioning of interrogator antennas is very critical, so make sure all antennas are placed scientifically, based on polarization and tag orientation. Conceal all antenna wires properly using insulation, making sure they don't overlap each other. Otherwise, this may lead to power loss and impact the read range.