CIRCULAR ARTIFICIAL DIELECTRIC MATERIAL OF ANISOTROPIC PERMITTIVITY AND ITS APPLICATION ON MICROSTRIP ANTENNA
The usage of natural dielectric materials in telecommunication devices have began todecrease,especiallysinceresearchersinthefieldofelectromagneticproposedthe artificial dielectric materials with many unique characteristics. Natural dielectric materials which are produced by facto...
Saved in:
| Main Author: | |
|---|---|
| Format: | Dissertations |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/27829 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | The usage of natural dielectric materials in telecommunication devices have began todecrease,especiallysinceresearchersinthefieldofelectromagneticproposedthe artificial dielectric materials with many unique characteristics. Natural dielectric materials which are produced by factories through the chemical processes have permittivity with limited value variations. This condition resulted difficulties in improving the performance of telecommunication devices. Unlike the natural dielectric material, the artificial dielectric material is made from the electromagnetismprocess,bymodifyingtheelectromagneticpropertiesofthenaturaldielectric material. These properties are expressed by a parameter called permittivity. By using this process, the permittivity of the material can be increased or converted into a new permittivity value which can’t be found in natural dielectric material, one of which is the anisotropic permittivity. <br />
<br />
<br />
<br />
The characteristic of anisotropic permittivity which is a tensor permittivity, has been explored by the researchers, whom are generally from Japan. One of the explorations are anisotropic permittivity capabilities in the miniaturization of the telecommunicationdevice’ssize. Miniaturizationofthetelecommunicationdevice’s size is needed especially for telecommunication devices which work on VHF frequencies and some frequencies on lower UHF frequencies. Technically, the miniaturizationsizeofthetelecommunicationdevicessuchasantenna,filter,power divider, and resonator require the use of high-permittivity dielectric materials. The literatures on miniaturization size of the telecommunication devices have proposed a method of increasing the permittivity value only by the x-, y- or z-direction. Within this case the anisotropic properties are described in a Cartesian coordinate system. <br />
<br />
<br />
<br />
The increased method of the permittivity value was done by adding small squareshaped conductor layers throughout the process of etching. These conductor layers were added on top of the natural dielectric material layer termed as host material. In this method, host material could be used only in the form of a printed circuit board or PCB. By setting the size, number, orientation and the density of the conductor layers as well as the distance between the conductor layers had effectively increased the permittivity value in a particular direction that affects the <br />
<br />
<br />
<br />
iv <br />
<br />
<br />
<br />
miniaturization of the size of the bandpass filter which is working on the TE01δ mode. Unfortunately,theexplorationoftheanisotropicpropertiesofmaterialswere only conducted by the Cartesian coordinate system and since 2006 the research on anisotropic dielectric material has not been developed yet. <br />
<br />
<br />
<br />
This dissertation develops a research on artificial dielectric material with an anisotropic permittivity in a cylindrical coordinate system. The anisotropic permittivity is set within the ρ-direction, φ-direction, and z-direction. This dissertation explores the anisotropic permittivity capability in miniaturization of telecommunication device’s size which has a circular physical construction. The exploration is done through theoretical, numerical and experimental studies. In theoretical and numerical studies, an artificial dielectric material with anisotropic permittivity is encapsulated in a circular cavity resonator. The resonator is termed asanartificialcavityresonator. Theresonantfrequenciesgeneratedbytheartificial cavity resonator have been characterized in TE and TM modes. The resonance frequency as a function of material thickness and anisotropic permittivity value has beenformulatedbyvariableseparationmethodandshortopenterminationmethod by considering the electrical field boundary conditions on the conductor walls of the circular cavity resonator. <br />
<br />
<br />
<br />
Thepotentialminiaturizationofthetelecommunicationdevice’ssizehasbeeninvestigated by comparing the resonant frequency which is generated by the artificial cavity resonator with the resonant frequency of a conventional cavity resonator. The conventionalcavity resonatoris amention of acircular cavityresonator which it is encapsulated by the natural dielectric material. In a numerical study, the resonant frequencies generated by the artificial and conventional cavity resonators have been calculated using the FDTD method. The FDTD method is constructed by the Maxwell equations of 3 dimensions in differential forms. The solution of the FDTD method is the time domain of electric and the magnetic fields amplitude that present in the artificial cavity resonator. Using FFT process, the resonant frequencythatgeneratedbytheartificialcavityresonatorcanbedetermined. From these studies, the results have shown that the resonant frequencies generated by the artificial cavity resonator are lower than the resonant frequencies generated by the conventional cavity resonator. In TE mode, anisotropic permittivity in the ρ-direction has resulted the highest percentage of resonance frequency lowering, especially in the dominant mode, i.e. TE11δ mode. The percentages generated from the theoretical and numerical studies are 13.77 % and 14.2 %, respectively. <br />
<br />
<br />
<br />
InTMmode,anisotropicpermittivityinthez-directionhaseffectivelydecreasedthe resonant frequency even if the percentage is higher than the TE mode percentage. In the dominant mode, which is the TM01 delta mode, the resonant frequencies generated through theoretical and numerical studies are 43.07 % and 42.52 %, respectively. While the other TM modes are 35.98 % and 37.95 % for TM11δ and 34,86 % and 36.35 % for mode TM21δ. From the results of theoretical and numerical studies, there are the potentials for selecting TE or TM wave modes on dielectric materials with anisotropic permittivity. Furthermore, the potential of anisotropic permittivity in miniaturization of telecommunication device’s sizes was <br />
<br />
<br />
<br />
v <br />
<br />
<br />
<br />
implemented on microstrip antenna devices. Microstrip antenna is designed and fabricated at VHF and UHF frequencies. The experiment within this dissertation is anisotropic permittivity in the z-direction. To generate anisotropic permittivity in the z-direction, the amount of 0.5 mm diameter conductor wires are implanted perpen-dicularly through the surface of host material. To increase the permittivity value in the z-direction, the wires are implanted in the position of the maximum electric field from the TM11 mode electric field distribution. <br />
<br />
<br />
<br />
Thehostmaterialthatisusedisadielectricmaterialwhichisavailableeasilyonthe market with a low cost, i.e. styrofoam, acrylic, floral foam, and FR-4 epoxy. The return loss of artificial microstrip antenna which is called for microstrip antenna is fabricated using the artificial dielectric material which has been measured and compared with return loss of conventional microstrip antenna. The conventional microstrip antenna which is a mention for a microstrip antenna that fabricated usinganaturaldielectricmaterial. Themeasurementhasbeenconductedbysetting dimension of both radiator microstrip antennas equally. From the measurement result, it result shows that the working frequencies of the artificial microstrip antenna on the four host material are lower than the working frequencies of the conventional microstrip antenna. The working frequencies are the frequencies in whichthereturn loss valueisboundednotless than10dB.Thebest result isshown when110conductorwiresareplacedthroughthesurfaceofstyrofoam. Thecentral frequency of the artificial microstrip antenna is lower than the frequency of the conventional microstrip antenna from 1832.3 MHz down to 1095.7 MHz. <br />
<br />
<br />
<br />
The results of theoretical, numerical and experimental studies have shown that the artificialdielectricmaterialwithanisotropicpermittivityinacylindricalcoordinate systems has a good potential in the miniaturization of the telecommunication device’ssize. Thepotentialhasbeendemonstratedbythelowresonantfrequencyin acircularcavityresonatorandthelowworkingfrequencyofthemicrostripantenna. The planting of conductor wires in the position of the maximum electric field of TE or TM modes can provide flexibility in setting the permittivity value of dielectric material. The permittivity setting capability can be taken into consideration by an engineer in the selection of an inexpensive artificial dielectric material type when miniaturizing the size of telecommunication devices as well as for the purpose of improving the performance of telecommunication equipment. <br />
|
|---|