The discussions in the following sections of this chapter are aimed at bridging that
knowledge gap. Finally, Section 4.5 illustrates a successful antenna design for a passive
RFID label that can be placed on corrugated cardboard boxes containing dry goods. The
antenna designs presented are of a ??????credit card size,??™??™ considered generally to be a suitable
size for labeling a majority of cases used in supply chain applications.
4.3.1 Nature of Antennas Suitable for RFID
This section will consider, in general, types of antennas suitable for RFID applications. The
evaluation will be based on both practical aspects and performance aspects. Considering
practicable antennas for RFID applications restricts us to mostly planar structures that can
be attached to items, cases, and pallets. In addition, it is important to consider the RFID
chip input impedance at the threshold of operation to realize a conjugate antenna impedance
to achieve maximum power transfer to the RFID label IC. Unlike other applications,
it is not cost effective to design elaborate matching circuits based on lumped circuit
elements to match the antenna impedance to the chip input impedance because it is
both expensive and structurally unsuitable for labels used in a majority of supply chain
applications.
Since passive RFID tags operate in a power-constrained environment created by electromagnetic
compatibility regulations and the power required to operate the tags is
obtained from the incident electromagnetic waves, maximum power transfer is of vital
importance.
Pages:
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157