In this thesis, a comparison of the body SAR value of five planar WLAN antennas including two coupled-fed shorted monopole antennas, a coupled-fed loop antenna, a monopole antenna, and a monopole slot antenna for tablet PC applications are presented. A required minimum distance between the antenna and the testing flat phantom to meet the 1-g body SAR requirement of 1.6 W/kg has been determined. Results show that the body SAR results of the coupled-fed loop antenna are lowest among the five tested antennas. Detailed results and discussion are presented in this thesis. Also, a comparison of the body SAR value of a planar antenna and an antenna with 3-D bent structure are presented.

Series-fed printed slot antenna arrays excited by microstrip lines are low profile, easy to manufacture, low cost structures that found use in applications that doesn&rsquo / t require high power levels with having advantage of easy integration with microwave front-end circuitry. In this thesis, design and analysis of microstrip line fed slot antenna arrays are investigated. First an equivalent circuit model that ignores mutual coupling effects between slots is studied. A 6-element array is designed by using this equivalent circuit model. From the measurement and electromagnetic simulation results of this array, it is concluded that mutual coupling effects should be considered in order to achieve a successful design that meets the design specifications related to the main beam direction and sidelobe levels of the antenna. Next, an improved equivalent circuit model proposed for stripline fed slot antenna arrays is studied. It is observed that, the mutual coupling effects are incorporated into the equivalent model through the utilization of active impedance concept. Finally, the design equations proposed in the improved equivalent circuit model are derived for the microstrip line fed slot antenna array structure. To demonstrate the validity and the accuracy of the derived design equations, results obtained by the proposed analysis method are compared with simulation and measurement results. It is concluded that the proposed method successfully predicts the radiation pattern of the array by including the mutual coupling effects.

Dielectric resonator antenna (DRA) technologies are applicable to a wide variety of mobile wireless communication systems. The principal energy loss mechanism for this type of antenna is the dielectric loss, and then using modern ceramic materials, this may be very low. These antennas are typically of small size, with a high radiation efficiency, often above 95%; they deliver wide bandwidths, and possess a high power handling capability. The principal objectives of this thesis are to investigate and design DRA for low profile personal and nomadic communications applications for a wide variety of spectrum requirements: including DCS, PCS, UMTS, WLAN, UWB applications. X-band and part of Ku band applications are also considered. General and specific techniques for bandwidth expansion, diversity performance and balanced operation have been investigated through detailed simulation models, and physical prototyping. The first major design to be realized is a new broadband DRA operating from 1.15GHz to 6GHz, which has the potential to cover most of the existing mobile service bands. This antenna design employs a printed crescent shaped monopole, and a defected cylindrical DRA. The broad impedance bandwidth of this antenna is achieved by loading the crescent shaped radiator of the monopole with a ceramic material with a permittivity of 81. The antenna volume is 57.0  37.5  5.8 mm3, which in conjunction with the general performance parameters makes this antenna a potential candidate for mobile handset applications. The next class of antenna to be discussed is a novel offset slot-fed broadband DRA assembly. The optimised structure consists of two asymmetrically located cylindrical DRA, with a rectangular slot feed mechanism. Initially, designed for the frequency range from 9GHz to 12GHz, it was found that further spectral improvements were possible, leading to coverage from 8.5GHz to 17GHz. Finally, a new low cost dual-segmented S-slot coupled dielectric resonator antenna design is proposed for wideband applications in the X-band region, covering 7.66GHz to 11.2GHz bandwidth. The effective antenna volume is 30.0 x 25.0 x 0.8 mm3. The DR segments may be located on the same side, or on opposite sides, of the substrate. The end of these configurations results in an improved diversity performance.

This thesis discusses Slot antennas that are based in gap waveguide technology, which allows them to work with high frequency signals. It contains theoretical findings about antennas and waveguides, which are later used in the design. The practical section of this thesis concentrates on designing a specific gap waveguide for 10 and 24 GHz frequencies, starting with modeling and parameter optimalization. This gap waveguide is then used as a base for slot antenna design. The final antenna is designed for frequency of 10 GHz, for both linear and right-handed circular polarizations. With right-handed circular polarization, the achieved band was approximately 1.41 GHz, while the gain was 7,6 dB.

Jednoduché dvojrozměrné anténní zářiče, které slouží jako stavební bloky anténních polí, jsou analyticky analyzovány v časové oblasti. Jako hlavní nástroj pro analýzu je použita Cagniard-DeHoopova metoda. Je ukázáno, že zvolený přístup umožňuje získat přesné vzorce v časové oblasti v uzavřeném tvaru, které jasně demonstrují vliv vstupních parametrů a objasňují fyzikální podstatu pulsního elektromagnetického vyzařování. Dané numerické výsledky ilustrují důležité aspekty pulsního elektromagnetického záření v rozličných konfiguracích problémů. Získané výsledky jsou užitečné pro efektivní návrh anténních polí, které jsou buzeny pulsními signály.

Disertační práce je zaměřena na vytvoření návrhu antény operující v blízkosti lidského těla. Kritické parametry zahrnují impedanční přizpůsobení, polarizační vlastnosti a vyzařovací charakteristiky. Základní výzkum je proveden na zjednodušených modelech lidského těla, kde jsou striktně definovány materiálové vlastnosti. Pro pokročilejší analýzu jsou využity detailnější modely. Simulace jsou konfrontovány s měřením na reálných vzorcích. V práci zahrnujeme interakci mezi anténou a lidským tělem.

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The infrared and millimeter-wave portions of the spectrum both have their advantages for development of imaging systems. Because of the difference in wavelengths, infrared imagers offer inherently high resolution, while millimeter-wave systems have better penetration through atmospheric aerosols such as fog and smoke. Shared-aperture imaging systems employing a common focal-plane array that responds to both wavebands are desirable from the viewpoint of overall size and weight. We have developed antenna-coupled sensors that respond simultaneously at 30 THz and at 94 GHz, utilizing electron-beam lithography. Slot-antenna designs were found to be particularly suitable for coupling radiation into metal-oxide-metal (MOM) tunnel diodes at both frequencies. The MOM diodes are fabricated in a layered structure of Ni-NiO-Ni, and act as rectifying contacts. With contact areas as low as 120 nm × 120 nm, these diodes have time constants commensurate with rectification at frequencies across the desired millimeter-wave and infrared bands. One challenge in the development of true focal-plane array imagers across this factor-of-300 bandwidth is that the optimum spatial sampling interval on the focal plane is different in both bands. We have demonstrated a focal plane with interleaved infrared and millimeter-wave sensors by fabricating infrared antennas in the ground plane of the millimeter-wave antenna. Measured performance data in both bands are presented for individual antenna-coupled sensors as well as for devices in the dual-band focal-plane-array format.

Dielectric resonator antenna (DRA) technologies are applicable to a wide variety of mobile wireless communication systems. The principal energy loss mechanism for this type of antenna is the dielectric loss, and then using modern ceramic materials, this may be very low. These antennas are typically of small size, with a high radiation efficiency, often above 95%; they deliver wide bandwidths, and possess a high power handling capability. The principal objectives of this thesis are to investigate and design DRA for low profile personal and nomadic communications applications for a wide variety of spectrum requirements: including DCS, PCS, UMTS, WLAN, UWB applications. X-band and part of Ku band applications are also considered. General and specific techniques for bandwidth expansion, diversity performance and balanced operation have been investigated through detailed simulation models, and physical prototyping. The first major design to be realized is a new broadband DRA operating from 1.15GHz to 6GHz, which has the potential to cover most of the existing mobile service bands. This antenna design employs a printed crescent shaped monopole, and a defected cylindrical DRA. The broad impedance bandwidth of this antenna is achieved by loading the crescent shaped radiator of the monopole with a ceramic material with a permittivity of 81. The antenna volume is 57.0  37.5  5.8 mm3, which in conjunction with the general performance parameters makes this antenna a potential candidate for mobile handset applications. The next class of antenna to be discussed is a novel offset slot-fed broadband DRA assembly. The optimised structure consists of two asymmetrically located cylindrical DRA, with a rectangular slot feed mechanism. Initially, designed for the frequency range from 9GHz to 12GHz, it was found that further spectral improvements were possible, leading to coverage from 8.5GHz to 17GHz. Finally, a new low cost dual-segmented S-slot coupled dielectric resonator antenna design is proposed for wideband applications in the X-band region, covering 7.66GHz to 11.2GHz bandwidth. The effective antenna volume is 30.0 x 25.0 x 0.8 mm3. The DR segments may be located on the same side, or on opposite sides, of the substrate. The end of these configurations results in an improved diversity performance. / General Secretariat of Education and Scientific Research Libya

No / A compact-size asymmetrical linearly tapered slot antenna required for portable ultra-wideband (UWB) imaging systems is presented. The total antenna size is reduced compared with the conventional linearly tapered slot antenna by using a triangular slot on the left-hand side of the tapered-shaped radiator, whereas introducing a corrugated pattern of cuts on the right side. The antenna operates over a wide bandwidth extending from 3.1 to 10.6 GHz with a maximum gain of 8.5 dBi. Stable radiation patterns are observed across the operational bandwidth, with cross-polarization levels below 20 dB. The realized antenna structure occupies a volume of 35 x 36 x 0.8 mm3, and possesses the essential time domain fidelity needed for UWB imaging applications. (c) 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.