15
A label antenna design methodology
illustrated using a simple ?¬‚ow chart to
outline the process steps.
Far-Field Tag Antenna Design Methodology 79
A simple approach is to consider a single element or two elements matching network
that will transform the antenna impedance to form a conjugate match to the chip impedance.
Such a matching network should then be physically implemented as part of the
antenna because the use of separate lumped circuit elements is an expensive, lossy, and less
area ef?¬?cient method.
The resulting RFID tags inevitably tend to be too complex for analytical investigation
and various numerical electromagnetic analysis software based on method of moments for
planar two-dimensional structures (MoM), ?¬?nite element method (FEM), or ?¬?nite difference
time domain (FDTD) method for more complicated three-dimensional structures may
be used.
Before using design tools, it is important to develop a simulation strategy and evaluate
the performance of the tools by comparing simulated results with those from analytical
and measurement results. Then, new antenna designs can be modeled and simulated to
obtain desired antenna gain, input impedance, and to understand the relationship between
tag antenna dimensions and antenna input impedance, which is critical for delivering
maximum power to the tag.
Once an optimal antenna design has been developed, prototypes of the antenna can be
built and their performance can be evaluated by taking read range measurements under
controlled conditions (such as an anechoic chamber) or in the practical environment in
which the tags are to be deployed.
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