4.5 Novel Reverse Design Method of Tag Antenna Based on Image Analysis
143
Fig. 4.24 Half-wave dipole
antenna model
line width of the impedance matching loop; and w is the width of the dipole
antenna.
The length of the half-wave dipole antenna is determined by Eq. (4.39):
L =
λ
2
=
c
2f
√
ε
(4.39)
Among them, c is the propagation velocity of light in vacuum, f is the center
frequency of the antenna, and ε is the relative dielectric constant.
The impedance value of the dipole antenna can be expressed as [15, 16]
Z in =
2Z t (1 + α)
2 Z A
2Z t + (1 + α)
2 Z A
(4.40)
Z in =
1
1
(1+α)
2 Z A
+
1
2Z t
(4.41)
The size of antenna impedance is determined by (1 + α)
2 Z A and Z t by (4.41). The
impedance between the antenna and the chip is Z A and the impedance between the
impedance loop and the antenna is Z t . The size is: