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Ch65-I044963.fm Page 321 Tuesday, August 1, 2006 4:44 PM
1, 2006
Tuesday, August
Page 321
4:44 PM
Ch65-I044963.fm
321
321
-5 -5
-10 -10

-15 -15
-20
-25

300 600 700 300 600 700 300 900
MHz MHz
a) b)
Figure 3: Simulated return loss SI 1 (dB) of a dipole antenna as a function of frequency.
a) Effect of relative permittivity (2.0, 2.5, 3.0, 3.5, 4.0, 5.0, and 6.0).
b) Effect of loss tangent (tan0.05, 0.1, 0.2, 0.3 and 0.4).

As the relative permittivity of both paper and the reel core increases the resonant frequency of dipole
antenna decreases noticeably as expected. Also the -10 dB bandwidth narrows, as the return loss gets
worse with the increasing relative permittivity.
The effect of loss tangent

The effect of loss tangent on properties of dipole antenna was studied for values 0.05, 0.1, 0.2, 0.3 and
0.4. The simulations were repeated for three different values of relative permittivity 2.0, 4.0 and 6.0.
The relative permittivity of the reel core was 3.0 and the loss tangent 0.1. In the Figure 3b) the change
in return loss due to change in loss tangent of paper is presented.

In the Table 2 the resonance frequency, return loss and bandwidth as a function of loss tangent of
paper are presented.

TABLE 2
THE EFFECT OF LOSS TANGENT ON RESONANCE FREQUENCY,
RETURN LOSS AND BANDWIDTH OF A DIPOLE ANTENNA.
tanS Resonance Sll Bandwidth Bandwidth
frequency (dB) (MHz) (%)
(MHz)
0.05 630 12.9 579...685 16.8
= 106
0.1 630 15.0 568...703 21.4
= 135
0.2 620 20.6 548...718 27.4
= 170
0.3 610 31.2 530...725 32.0
= 195
0.4 600 29.7 515...723 34.7
= 208

For the simulated cases the return loss increases with increasing the value of loss tangent. Also the
resonant frequency decreased slightly when increasing losses. The -10 dB bandwidth increases as the
return loss increases and the matching of the antenna gets better.