The simulation tools can be used to create a better understanding of the functioning of
the bow-tie antenna and con?¬?rm expectations. Figure 4.31 shows the surface current
distribution on the bow-tie antenna as it is fed with an oscillating current. The diagrams
show the current traversing from the feed point, outward toward the end of the bow-tie
wings, over a period of p=2 of the oscillating current.
A practical construction of the tag can be achieved using copper sheets 0.035 mm in
thickness or more to the speci?¬?cations given in Table 4.9 and the description given in Figure
4.25. Then an RFID strap can be attached to the antenna terminals using a conductive
adhesive. Figure 4.32 shows one of the antennas constructed in the laboratory for testing
purposes. Read range measurements (conducted in an indoor laboratory environment) of
0
20
40
60
80
100
120
140
160
180
850 860 870 880 890 900 910 920 930 940 950
0
5
10
15
20
25
Reactance
Real impedance
Frequency (MHz)
Real impedance ()
Reactance ()
FIGURE 4.29
BowS impedance variation over a frequency range of 850??“950 MHz obtained from simulated results.
Bow-tie
antenna
q = 0
q = /2
04.00
3.01
2.03
1.04
30
60
90
120
150
180
150
4.0 4.0 0.05
120
90
60
30
FIGURE 4.30
The radiation pattern of BowS antenna obtained from
simulated results.
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