User's Manual

COBALT UHF-SERIES CHAPTER 9: RFID OVERVIEW
PAGE 130 OF 140
9.2.2 UHF Signal Propagation
In general, the frequency defines the data transfer rate (speed) between the tag and
the reader. For this reason, UHF systems feature long range, and high speed
read/write rates.
Small antennas and even smaller tags have proven this to be an effective frequency
for tracking pallets through dock doors, as well as trucking and transportation
applications. Industrial UHF applications have also begun to effectively be developed
for tracking parts, product and carriers through production.
In this context, Cobalt UHF is ideal for industrial applications where single or multiple
tags must be read at long distance and at high speed.
The main advantage of UHF transmission is the physically short wave that is
produced by the high frequency. The size of transmission and reception equipment,
(particularly antennas), is related to the size of the radio wave.
The higher the frequency, the shorter the wavelength for RF transmission. Without
going into the details of the physics, the shorter the wavelength, the better a small
antenna like an RFID tag is able to receive a transmission at greater distances.
Therefore, smaller and less conspicuous antennas can be used with higher
frequency bands.
For the Cobalt UHF- Series product line, Datalogic offers a range of circular polarized
antennas, for which tag orientation is less critical.
In effect, the helical nature of the field from a circular polarized antenna allows it to
read tags in random orientation.
Figure 9-3: Circular Polarized Antenna’s Field Pattern