The two different physical constructions (as shown in
Figures 4.26 and 4.27) were built to evaluate their performance.
Figures 4.28 and 4.29 show the impedance variation of the two bow-tie antenna designs
over an operational frequency range of 850??“950 MHz. The change in real impedance over
FIGURE 4.24
A bow-tie antenna with a series tuning inductor.
z
y x
FIGURE 4.25
Bow-tie antenna design structure with a series inductor.
hB
g lw
ic
fx
fy
iw
86 RFID Handbook: Applications, Technology, Security, and Privacy
the frequency range is similar for both designs and neither design provides an advantage
in impedance variations over frequency. Both designs can be expected to maintain a
reasonably low-radiation quality factor over a range of frequencies with the added bene?¬?t
of being able to better mitigate the detuning effects from environmental factors.
TABLE 4.7
Bow-Tie Antenna Input Impedance Characteristics
Rr CB LB hb Input Impedance
25 V 0.8 pF 23.1 nH 80 mm 25 ??“ 84j
TABLE 4.8
Simulation Results
hb
(mm)
lw
(mm)
iw
(mm)
ic
(mm)
g
(mm)
fy
(mm)
fx
(mm)
Input Impedance
(V)
71 1 6 2 9 1 1 17.00??122.00j
71 1 7 5 9 1 1 16.47??93.54j
72 1 7 5 8 2 1 16.82??98.50j
72 1 7 2 8 2 1 18.75??142.65j
72 1 7 2 8 2 2 18.97??141.61j
72 2 9 2 8 2 1 16.165??93.14j
72 1 4 3 8 2 1 17.68??80.35j
74 1 6 2 9 1 2 20.35??146.
Pages:
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186