Introduction To Antenna Selection And Configuration For RFID Readers

RFID readers operating at UHF frequencies (around 900 MHz) are coming into increasing use in a variety of applications. Many of these applications fall into one of three categories: portal, conveyor, or handheld configurations. The readers employ either external or built-in antennas to communicate with the tags. These antennas must be selected and configured to satisfy the specific requirements of each application category. In this article we introduce some fundamental antenna characteristics and then review the application requirements. Future articles will cover the process of finding the appropriate antenna parameters for each requirement.

Antennas are the means by which the voltages generated by the RFID reader are converted into electromagnetic waves to communicate with the tags, and the scattered waves from the tags are converted back into voltages. The characteristics of the reader antenna, combined with the method of installation and use, often determine whether an RFID tag can be read successfully. As the hardware cost of readers decreases the relative contribution of the cost of site evaluation and installation has become a more significant part of the total installation cost. Careful selection and placement of antennas is a critical consideration for successful low cost deployment.