Two laptop antennas are presented using two different designs based on metamaterials. The first design consists of planar monopole loaded with an electric-LC resonator (ELC). This novel topology allows for the realization of a multi-band antenna by using the ELC to add multiple resonances. This structure is analyzed using full-wave simulations. A circuit model is also developed to gain further understanding. This technique is then used to design a Wi-Fi antenna. The second design uses a modified double-tuned matching network to create a single-band match for a planar monopole antenna. The matching network is implemented using a complementary-split-ring-resonator (CSRR). The design is once again analyzed using full-wave simulations and a circuit model is also developed. This technique is then applied to design a WiMax antenna. Both the Wi-Fi and WiMax antennas are fabricated and show good agreement between the simulated and measured results.

One goal of this thesis is to address several challenging compact antenna design issues by using transmission-line metamaterials. In particular, we demonstrate the design of a compact antenna with an extended bandwidth, multiband/multifunction compact/small antennas, and mutual-coupling reduction for two closely-spaced small antennas. The proposed compact transmission-line metamaterial antenna employs the concept of zeroth- index resonance and a wideband characteristic is enabled by detuning the resonance of each constituent metamaterial unit cell at a slightly different frequency, thus creating a multi-resonant return-loss passband. Furthermore, a single-cell transmission-line metamaterial loading scheme is applied to regular printed monopole antennas in order to introduce additional resonances at the low band and create multiband small antennas that meet the specifications for WiFi and WiMAX applications. Lastly, a simple ap- proach for reducing the mutual coupling in two closely-spaced small antennas is also presented, based on the idea of self-cancelation of the induced currents. The other important goal of this thesis is to develop volumetric negative-refractive- index transmission-line (NRI-TL) metamaterials. A volumetric NRI-TL slab is created by stacking 2D NRI transmission-line grids in the shunt-node configuration. This is done in a simple manner through images induced in a parallel-plate environment. Additional vias are strategically placed to suppress the parasitic parallel-plate mode. Moreover, multiconductor transmission-line theory is used to model the volumetric metamaterial slab. A fully-printed volumetric Veselago-Pendry transmission-line lens is designed and matched to free space. Using this proposed lens, it has been experimentally verified that the diffraction limit can be overcome.

One goal of this thesis is to address several challenging compact antenna design issues by using transmission-line metamaterials. In particular, we demonstrate the design of a compact antenna with an extended bandwidth, multiband/multifunction compact/small antennas, and mutual-coupling reduction for two closely-spaced small antennas. The proposed compact transmission-line metamaterial antenna employs the concept of zeroth- index resonance and a wideband characteristic is enabled by detuning the resonance of each constituent metamaterial unit cell at a slightly different frequency, thus creating a multi-resonant return-loss passband. Furthermore, a single-cell transmission-line metamaterial loading scheme is applied to regular printed monopole antennas in order to introduce additional resonances at the low band and create multiband small antennas that meet the specifications for WiFi and WiMAX applications. Lastly, a simple ap- proach for reducing the mutual coupling in two closely-spaced small antennas is also presented, based on the idea of self-cancelation of the induced currents. The other important goal of this thesis is to develop volumetric negative-refractive- index transmission-line (NRI-TL) metamaterials. A volumetric NRI-TL slab is created by stacking 2D NRI transmission-line grids in the shunt-node configuration. This is done in a simple manner through images induced in a parallel-plate environment. Additional vias are strategically placed to suppress the parasitic parallel-plate mode. Moreover, multiconductor transmission-line theory is used to model the volumetric metamaterial slab. A fully-printed volumetric Veselago-Pendry transmission-line lens is designed and matched to free space. Using this proposed lens, it has been experimentally verified that the diffraction limit can be overcome.

<p>The demand for higher bit rates to support new services and more users is pushing wireless systems to millimetre-wave frequency bands with more available bandwidth and less interference. However at these frequencies, antenna dimensions are dramatically reduced complicating the fabrication process. Conductor loss is also significant, reducing the efficiency and gain of fabricated metallic antennas. To better utilize millimetre-wave frequencies for wireless applications, antennas with simple fabrication, higher efficiency, and larger impedance bandwidth are required.</p> <p>Dielectric Resonator Antennas (DRAs) offer many appealing features such as large impedance bandwidth and high radiation efficiency due to the lack of conductor and surface wave losses. DRAs also provide design flexibility and versatility. Different radiation patterns can be achieved by different geometries or resonance modes, wideband or compact antennas can be provided by different dielectric constants, and DRAs can be excited by a wide variety of feeding structures. Nevertheless, compared to their metallic counterparts, fabrication of DRAs is challenging since they have traditionally been made of high permittivity ceramics, which are naturally hard and extremely difficult to machine and cannot be easily made in an automatic way. The fabrication of these three dimensional structures is even more difficult at millimetre-wave frequencies where the size of the antenna is reduced to the millimetre or sub-millimetre range, and tolerances to common manufacturing imperfections are even smaller. These fabrication problems restrict the wide use of DRAs, especially for high volume commercial applications.</p> <p>A new approach to utilize the superior features of DRAs for commercial applications, introduced in this thesis, is to exploit polymer-based resonator antennas (PRAs), which dramatically simplifies fabrication due to the natural softness and results in a wide impedance bandwidth due to the low permittivity of polymers. Numerous polymer types with exceptional characteristics can be used to fulfill the requirements of particular applications or achieve extraordinary benefits. For instance, in this thesis photoresist polymers facilitate the fabrication of PRAs using lithographic processes. Another advantage derived from this approach is the capability of mixing polymers with a wide variety of fillers to produce composite materials with improved or extraordinary characteristics.</p> <p>The key contributions of this thesis are in introducing SU-8 photoresist as a radiating material, developing three lithographic methods to fabricate photoresist-ceramic composite structures, introducing a simple and non-destructive measurement method to define electrical properties of the photoresist composites, and demonstrating these structures as improved antenna components.</p> <p>It is shown that pure SU-8 resonators can be highly efficient antennas with wideband characteristics. To achieve more advantages for RF applications, the microwave properties of photoresists are modified by producing ceramic composite materials. X-ray lithography fabrication is optimized and as a result one direct and two indirect methods are proposed to pattern ultra thick (up to 2.3 mm) structures and complicated shapes with an aspect ratio as high as 36:1. To measure the permittivity and loss tangent of the resulting materials, a modified ring resonator technique in one-layer and two-layer microstrip configurations is developed. This method eliminates the requirement to metalize the samples and enables characterization of permittivity and dielectric loss in a wide frequency range from 2 to 40 GHz. Various composite PRAs with new designs (e.g. frame-based and strip-fed structures) are lithographically fabricated, tested, and discussed. The prototype antennas offer -10 dB bandwidths as large as 50% and gain in the range of 5 dBi.

For applications of wireless communication of the fourth generation (4G LTE), the technique of using a printed parallel-resonant spiral strip for bandwidth enhancement of a small-size planar laptop computer (especially the thin Ultrabook) antenna for the LTE operation is first presented. The antenna is printed on a thin FR4 substrate of small size 45 x 9 mm2 with a simple uniplanar structure which is promising for Ultrabook application. Based on the proposed antenna structure, its application for MIMO operation to achieve enhanced isolation is also analyzed in this thesis. Different from the works for the relatively much smaller ground plane conditions such as in the mobile phones, the effect of different size of the supporting conductive plate of the upper corner of the Ultrabook is discussed for the isolation issue of the MIMO antennas. Finally, the technique of isolation improvement in the LTE700 band for the MIMO operation in the Ultrabook is presented.

In this dissertation, EMC antennas for mobile communication device applications are proposed. This kind of EMC antennas can overcome the problem that happens to the conventional antenna; in practical application, when electronic components are placed very close to the conventional antenna, large degradation of the antenna performance will occur. In the proposed EMC antennas, by adding a vertical antenna ground plane functioning as a shielding metal wall, EM coupling between the EMC antenna and nearby components can be reduced. Thus, it leads to no degradation or only negligible variations of the antenna performance. Also, the concept of EMC antennas can be applied to the monopole antenna. One of the examples suitable for the future thin (< 10 mm) mobile communication device is demonstrated. Further, the user¡¦s hand effects on EMC antenna performance are analyzed. Even when the mobile phone is hand-held at the bottom, large radiation efficiency drops are observed, especially for the GSM band.

In this thesis, three small-size internal multiband antennas for laptop computer application for different wireless communication systems are proposed. In the first design, the coupling feed is incorporated to the planar inverted-F antenna to achieve a dual-resonance excitation in the lower band such that the obtained bandwidths can easily cover GSM850/900/DCS/PCS/UMTS operation. The effect of the user¡¦s hand on the antenna is also studied. In the second design, we introduce the T-shaped coupling feed used in the PIFA for successful excitation of two wide operating bands to cover WLAN operation in the 2.4 GHz band and 5.2/5.8 GHz band, and the size reduction is even larger than 50%. Finally, a multiband monopole antenna with a band-notching slit is proposed. By embedding the slit of length about a quarter-wavelength at about 4 GHz, a band-notching characteristic is obtained, which leads to an additional resonance at about 3.5 GHz. Hence, three wide operating bands for covering all the desired operating bands of WLAN/WiMAX systems are achieved for the proposed antenna.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Michael Melich, David Jenn, Rodney Johnson. Includes bibliographical references (p. 71-72). Also available online.

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 87-93).

Thesis (M.S. in Systems Engineering)--Naval Postgraduate School, September 2003. / Thesis advisor(s): David C. Jenn, Richard W. Adler. Includes bibliographical references (p. 71-72). Also available online.