0 sc0 ls0 ws5">(a) (b) (c) (d)
Figure 2. The (a) top, (b) side, (c) metal slab with bottom and (d) magnetic slab with bottom view of antenna.
W.-C. Lai, C.-L. Wu
271
(a) (b)
Figure 3. The return loss of (a) metal slab and (b) magnetic slab of the monopole antenna as a function of the spacing.
(a)
(b)
Figure 4. Simulated and measured pat terns as a function of distance d between the (a) metal slab and (b) magnetic slab and
the ground plane of monopole antenna.
W.-C. Lai, C.-L. Wu
272
(a) (b)
Figure 5. Measured gains as a function of distance d between (a) metal slab and (b) magnetic slab and the ground plane of
monopole antenna.
frequency (2.4 GHz). It is shown that the measured data are in excellent agreement with the simulated one. In
Figure 4(a), a metal slab with thickness of 0.9 mm is employed in the experiment. When metal slab is placed on
the ground side of the monopole antenna, the pattern changes significantly as the distance d increased. The
E-plane radiation pattern becomes directional compared to the one of the classical monopole at θ = 0˚. Again, in
Figure 4(b) [10], a magnetic slab with thickness of 1 mm is employed in the experiment. When magnetic slab is
placed on the ground side of the monopole antenna, the pattern also changes. The E -plane radiation pattern be-
comes directional compared to the one of the classical monopole [11] at θ = 0˚, 180˚. The pattern of the antenna
is omnidirectional when the magnetic slab is absent. The pattern changes gradually as the magnetic slab moves
farther from the grounding plate of the antenna.
3.3. Effect of d on the Gain of the Ground Shielding
Figure 5 shows the gain variation of antenna system as a function of d for the metal or magnetic slab. In the
metal slab case as Figure 5(a), the antenna gain always less than without slab of monopole antenna at θ = 180˚.
When d = 10.5 mm, the antenna gain start large than without slab of monopole antenna at θ = 0˚. When d =
35.86 mm, it can increase the antenna gain to 4.6 dB at θ = 0˚. In the magnetic slab case as Figure 5(b) [10], the
gain is less than 0 dB as d < 15 mm. As d > 20 mm, the magnetic slab acts as a reflector so that appreciable gain
is obtained. On the other hand, Figure 5 shows the antenna gain as a function of d for different values of mag-
netic slab thickness at θ = 180˚. The antenna has appreciable gain for 10 mm < d < 30 mm. The optimal gain
occurs when 14 mm < d < 16 mm. The max. gain 3 dB holds for a large range of d.
4. Conclusion
A planar monopole antenna with reconfigurable radiation pattern is presented. It is found that, the presence of
metal slab with thickness of 0.9 mm will yield reflection e ffects, which can increase the antenna gain to 4.6 dB
at θ = 0˚ and produce desirable radiation pattern. In other hand, the prese nce of magnetic slab with thickness of
1 mm will yield refraction or reflection effects, which can increase the antenna gain to 3 dB at θ = 180˚ and
produce desirable radiation pattern. The measured results are in good agreement with the simulated results, as
shown in Fig ure 4. So we can see that metal slab better than magnetic slab in this verification. It seems that we
placed items inadvertently in the general household, but it inducing electromagnetic will influence the power
system [12].
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