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Abstract

This thesis describes design for the miniaturization and the broad bandwidth of antennas using the Magneto-Dielectric Material (MDM). When the electromagnetic wave penetrates the MDM with high relative permittivity and high relative permeability, wavelength distance appears longer than in free space. Therefore, the MDM has been generally employed for antenna miniaturization even though it has tangential loss terms .

A design for feeding probe structure with the cylindrical magento material (CMM) to realize the miniaturized antenna with high gain and broad bandwidth had been proposed in Chapter 2. Feeding probe is perfectly closed by the CMM structure. The magnetic currents generated by feeding probe are induced to the CMM. The feeding probe current and the induced CMM current are strongly coupled by the Ampere's law. A strongly coupled magnetic current is transmitted to antenna surface. It will be increase the gain in conclusion even it depends on tangential loss of materials. When single CMM applies to increase gain of antenna, antenna miniaturization turns out about average 112% and gain increases about average 3.96 dB. However, the bandwidth is still remained to compare with the reference antenna without CMM. The dual CMM is considered to improve the frequency bandwidth. The proposed antenna with dual CMM became about 230% miniaturization, the bandwidth increase of 139% toward low frequency band direction and the gain increase of average 10 dB. It means that antenna can be minimized by control of relative permeability as well as the parameters between feeding line and magnetic material.

This thesis describes what material is the suitability for broad bandwidth method of antenna using cylindrical magneto material and cylindrical dielectric material in chapter 3. When the thickness() of magnetic material equals to about 0.04 , the bandwidth is improved about with ± 3.2 % error rate. is the distance from feeding probe to inner CMM. The result of proposed approximated equation agrees well with the simulated result by commercial tool of HFSS.

In chapter 4, a broad bandwidth RFID tag antenna design for protection of connection part between chip and antenna presented. This tag antenna will be a good candidate to apply the magnetic material for miniaturization and bandwidth control.

The conclusion of thesis appears in chapter 5.