In this thesis, an LTE/WWAN planar loop antenna for tablet computer with a compact size of 75 ¡Ñ 12 mm2 is presented. The planar loop antenna comprises a printed loop strip and a patch monopole encircled therein. By embedding a printed distributed inductor in the loop strip, whose effect is similar to a chip inductor, a parallel resonant mode is generated owing to the contributed inductance of the distributed inductor and the contributed capacitance of the coupling between the loop strip and the patch monopole. The parallel resonant mode leads to increase input resistance of the 0.5-wavelength loop mode at the high-frequency tail and a zero reactance nearby the original resonance of the 0.5-wavelength loop mode, thereby resulting in a dual-resonance excitation to greatly enhance the bandwidth of the antenna¡¦s lower band for the LTE700/GSM850/900 operation. In addition, the patch monopole, which performs not only as a coupling feed but also an efficient radiator, provides a 0.25-wavelength resonant mode to combine with a higher-order resonant mode contributed by the printed loop strip to form the antenna¡¦s upper band to cover the GSM1800/1900/UMTS/LTE2300/2500 operation. Further, the required distance between the antenna and the testing flat phantom to meet the 1-g body SAR requirement of 1.6 W/kg is discussed. A comparison of the body SAR value of the planar loop antenna and the bent loop antenna is also discussed.

The research of this thesis is on the mobile TV antenna designs. There are three antenna designs proposed in this thesis. The first two designs are for portable TV sets. They are different from the traditional straight monopole antenna because the two proposed designs can be built-in with the portable TV set. The third one is for laptop applications. It can be stored inside a laptop when the antenna is not in use, and can be pulled out of the laptop when in operation. Thus the proposed antenna will not affect the appearance of the laptop.

In this thesis, the properties of the metamaterials are studied. We analyze and discuss the artificial structure called metamaterials. The the effects on the radiation pattern and antenna gain are discussed when the structure is placed above the antenna. First, the propagation of electromagnetic wave in metamaterials is discussed. The metamaterial composed of metal rod array and split-ring is introduced. Next, the effects on permittivity, permeability and refraction index are studied when the structure parameters are changing. Thirdly, according to the above-mentioned summary, we use the structures to achieve an antenna radome. The radome can reduce 3 dB beam-width by about 31.25 percent at 10.75 GHz. The maximum gain achieves 7.25 dBi. In the fourth part, we also discusse the method of reducing the frequency band where negative refraction index occurs. The metamaterial is used to be a radome at the lower frequency band. The maximum gain is about 7.87 dBi. The 3 dB beam-width reduces by about 37.25 percent by the radome structure. Fifthly, the methods of improving the bandwidth are discussed when the antenna radome over the antenna . The enhancement of the antenna performance can be applied to the point-to-point communication. It also can save the cost of the feed network and the numbers of array antenna.

In this thesis, we propose tag and reader antennas which are suitable when attended to metal material for Radio Frequency Identification (RFID) systems. For tag antenna design, we use microstrip antenna with ground plane to reduce the metal effect. In order to match the impedance of different IC chip, some parameter of the tag antenna are designed and described, which can be used to adjust the impedance of tag antenna. For reader antenna design, circularly polarized patch antenna can be achieved by using dual-feeding technique with U-shaped aperture-coupled, where the dual feeds with a phase shift and equal input power amplitude are provided by a Wilkinson power divider. Therefore, a good right-hand circular polarization is obtained and a 3-dB CP bandwidth of the designed reader antenna is greater than 30 ¢H. 900 We then design dual-band antenna and broad CP bandwidth antennas. In the dual-band design, two resonant paths are utilized to cover 915 and 2450 MHz bands that can be used for RFID systems in UHF and ISM bands. In the broad CP bandwidth design, a square slot antenna is used with a cross patch placed at the center of the square slot. Two orthogonal resonant modes with phase difference and equal input power amplitude can be excited by choosing the proper dimensions of the cross patch. A 3-dB CP bandwidth of the designed circularly polarized antenna is greater than 12¢H.

In this thesis, the relation between the fractal structure and the performance of the antennna is discussed. From the simulation and theoretical analysis , we can conclude that the 10dB impedance bandwidth of the monopole decreases when the iteration level of the fractal structure increases . Then we use the fractal structure to design the LTCC antenna. We design and manufacture an LTCC antenna for WLAN IEEE 802.11a. The simulation and measured results are analyzed and discussed. Finally, we provide a new method which can reduce the cross polariztion level. And this method is used to reduce the cross polarization of the monopole using the second iteration level of the Minkowski curve. It is shown that the method does work from the measurement. This method can reduce the cross polarization of the fractal antenna and hence find more application in communication systems.

In this thesis, we will firstly study the capacitive surface. By combining it with microstrip antenna, we can understand its effects on the properties of antenna, and investigate its miniature property. Next, we will design an electromagnetic band-gap (EBG) structure without vias to reduce the fabrication cost, and propose a best way of surrounding to combine EBG with antenna. In this way, we can improve the shortcomings of microstrip antenna, such as low gain and back radiation, etc. We will also apply our EBG to MIMO to reduce the mutual coupling and enhance gain. Then we make the MIMO antennas in a mobile device possible by shortening the distance between antennas. Finally, we can effectively shorten the distance and enhance performance even more by using miniature EBG. Both the fabrication and measurement will also be performed.

In this dissertation, the study mainly focuses on small-size multiband mobile phone antennas for practical applications. Loop antenna is chosen to be the antenna type for designing the compact internal multiband antenna. Four antenna designs are presented, including ¡§Compact Multiband Folded Loop Chip Antenna for Small-Size Mobile Phone¡¨, ¡§Very-Small-Size Folded Loop Antenna with a Band-Stop Matching Circuit for Penta-Band Mobile Phone Application¡¨, ¡§Very-Small-Size Printed Loop Antenna for GSMDCSPCSUMTS Operation¡¨, and ¡§Printed Loop Mobile Phone Antenna with an Internal Printed Matching Circuit¡¨. The first two antenna designs occupy a volume of 1.0 cm3 and 0.6 cm3 respectively and the last two antenna designs are to be directly printed on the system circuit board of the mobile phone. Either of them can operate as a quad-band antenna for GSM/DCS/PCS/UMTS operation or as a penta-band antenna for GSM850/900/1800/1900/UMTS operation.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 174-175).

Invented in 1935, Frequency Modulation (FM) is one of the most widely used analog modulation techniques in telecommunications. Since its inception FM radio has been used for high-fidelity music and speech broadcasting, offering excellent sound quality, signal robustness and noise immunity. Recently, FM Radio has witnessed an explosion of interest for its applications in mobile and personal media players (PMP). However, the traditional FM requires a long antenna, such as a wired headphone, which limits its usefulness for many users who do not carry a wired headset. This paper introduces FM solutions that enable the antenna to be integrated or embedded inside the device enclosure, thereby optimizing the end solution for portable consumer electronics. / text

Patch antenna is one of the most rapidly popular topics in the antenna field in the past twenty years. In high-performance aircraft, spacecraft, satellite and missile applications, where size, weight, cost, performance, ease of installation, and aerodynamic profile are constraints, low profile antennas may be required. [7]. The project is to develop a single patch antenna operating on a specific frequency 1420MHz. The frequencies near to 1420MHz are worth to observe because the hydrogen in throughout of the space can be mapped by the observation of the 21 – cm wavelength line which is corresponding to 1420 MHz radiation. The final product antenna will be used in a radio telescope as a part of the signal receiving system. The work within the project contains simulation, fabrication and test of final antenna. The simulation work was carried out in advanced design system which is developed by Agilent technologies, USA. The most different feature of the project is that, comparing to normal patch antenna, usually 50 ohms is selected as the matching impedance, while in this project we made it conjugate to the input impedance of the LNA. In this way we can save extra components, as well as energy consuming.