| Microwave photonic crystal is also called Electromagnetic Band-gap structure. The structure possesses two unique properties:in-phase reflection band gap and forbidden band gap. Surface wave impedance changes along with the frequency. By the use of surface wave band gap, the spread of antenna surface wave in the substrate is suppressed effectively, high directional antenna is obtained. Meanshile, in-phase reflection band gap can help to design low profile reflector antenna. To meet the need of high frequency and dual band antenna, high gain, low profile and high effiency antenna can be obtained by use of the EBG structrues’ special properties. The main results of the thesis are as follows:Firstly, the performance improvement of60GHz dielectric resonator antenna based on EBG structure is studied. Two kinds of high gain dielectric resonator antenna in60GHZ system are provided:one is based on PCB technology, and the other one is based on LTCC technology. Refer to the antenna based on PCB process, the performance is improved a lot with only one EBG circle embedded. The antenna gain is increased by3dB without worsen the general antenna size. Another novel antenna is designed in accordance with the requirement of low-temperature cofired ceramic (LTCC). A newly developed electromagnetic band-gap (EBG) structure is used to improve the antenna performance. It is shown that by embedding this special structure, it’s possible to enhance the antenna gain without disturbing the bandwidth property nor increasing the dimension. In the final antenna design, an increase of more than2.8dB is predicted in the gain. The radiation performance is also significantly improved. The presented design is a good candidate for60GHz application due to its high gain and high radiation efficiency. Secondly, a dual-band coaxial feed patch antenna based on one-dimensional EBG structure is designed. The given high-gain antenna structure can work on both2.45GHz and5.8GHz frequency region. By unitlizing the one-dimensional EBG structure, the minimum antenna gain within2.45GHz frequency range is increased from3dB to9dB, and the maximum gain value is improved from4dB to10dB. The improvements can also be observed for the5.8GHz region:the minimum gain value is increased from1dB to7dB and the maximum gain value is increase from1.5dB to8dB. The overall gain increasement is more than6dB.Finally, performance of a dual-band coplanar waveguide fed antenna (DB-CPWFA) loaded with a reflector is presented. The reflector is made of an electric ground plane, a dielectric substrate and artificial magnetic conductor (AMC) with an effective dual operational bandwidth. Then the closely spaced AMC reflector under the DB-DPWFA is employed for performance improvement including uni-directional radiation, low profile, gain enhancement and higher front-to-back (F/B) ratio. The final antenna design exhibits an8%and13%impedance bandwidth for2.45GHz and5.8GHz frequency respectively. The overall gain enhancement of about4dB is achieved. The F/B ratio is approximate to20dB with a16dB improvement. The presented design is a suitable candidate for radio frequency identification (RFID) reader application. |
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