Novas técnicas de otimização de casamento de impedância de antenas planares para sistemas de comunicação sem fio
The work presented in this dissertation consists in the development of new techniques for the impedance matching optimization of printed antennas for wireless communication systems. The techniques proposed are based on the insertion of slots in the antenna feeding line or below it (in the ground...
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| Formato: | doctoralThesis |
| Idioma: | pt_BR |
| Publicado em: |
Brasil
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/28350 |
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| Resumo: | The work presented in this dissertation consists in the development of new techniques
for the impedance matching optimization of printed antennas for wireless communication
systems. The techniques proposed are based on the insertion of slots in the antenna feeding line
or below it (in the ground plane), enabling to keep unchanged the patch geometry of the
investigated microstrip antenna. The study was performed using a parametric analysis and
enabled the development of three new impedance matching techniques. In the first, the insertion
of the slot is carried out in the conducting strip of the microstrip line, being symmetrically
placed. In the second, the slot is introduced into the ground plane, but it is inserted below and
parallelly to the conducting strip of the microstrip line. In the third, the slot is also positioned
in the ground plane, but is aligned parallel to the lower edge of the conducting patch, i.e.
perpendicularly to the conducting strip of the microstrip line. The effect of the input impedance
matching on the performance of rectangular patch microstrip antennas printed on fiberglass
substrates (FR-4) was investigated. The antennas were fed by microstrip lines and designed for
operation at 1.8 GHz, 2.45 GHz, and 3.5 GHz. Simulation and parametric analyses were
performed using Ansoft Designer and Ansoft HFSS softwares, that implement the method of
moments (MoM) and the finite element method (FEM), respectively. In addition, the wave
concept iterative procedure (WCIP) was also used in the analysis, enabling a better comparison
between the obtained simulated results. For validation purpose, several prototypes were
fabricated and measured. The good agreement observed between simulated and measured
results confirms the efficiency and accuracy of the new impedance matching techniques. The
proposed techniques are easy to implement and allow considerable reductions in the reflection
coefficient value, | S11 | (dB), indicating that the antenna efficiency was significantly increased.
In the first case, for the slot inserted in the conducting strip of the microstrip, the value of | S11
| (dB) was reduced from -8.81 dB to -28.09 dB in the analysis for 2.45 GHz. In the second case,
for the slot inserted in the ground plane, below and parallel to the conducting strip of the
microstrip, the value of | S11 | (dB) was reduced from -7.62 dB to -37.17 dB in the analysis for
2.45 GHz. In the third case, for the slot inserted in the ground plane, parallel to the lower edge
of the conducting patch, the value of | S11 | (dB) was reduced from -10.11 dB to -34.1 dB in
the analysis for 1.8 GHz. The use of slots, as proposed in this work, enabled a good impedance
matching between the antenna and the microstrip feeding line, avoiding the use of high impedance microstrip lines, abrupt transitions in the width of microstrip lines, changes in the
shape of the antenna conducting patch, or increasing the antenna size. |
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