Thesis (doctoral)--Helsinki University of Technology, 2008. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (M.S.)--Ohio University, November, 2005. / Title from PDF t.p. Includes bibliographical references (p. 111-118)

Thesis (M.S.)--Ohio University, June, 2004. / Title from PDF t.p. Includes bibliographical references (p. 131-133)

Thesis (Ph. D.)--Ohio State University, 1972. / Includes vita. Includes bibliographical references (leaves 206-213). Available online via OhioLINK's ETD Center.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Also available in electronic version.

The primary focus of this dissertation is on the analyses of self-resonant bent antennas. The need for the accurate characterization of such antennas due to their growing importance in present day wireless communications is the motivation for this work. To this end, several self-resonant bent antennas are analyzed which includes an inverted-L antenna (ILA), a meander-line dipole (MLD) antenna, a meander-line bow-tie (MLBT) antenna, a dual meander antenna, and a printed meander antenna. A simple analytical model, based on the induced EMF method, is presented to compute the input impedance of the ILA. First, a sinusoidal distribution of current on the antenna, with zero current at the end is assumed, and then an expression for the input impedance is derived using the near-fields of the antenna. The accuracy of the formulation is verified by comparing the results computed using it with that from NEC [1] computation. Unlike the analytical solutions available in the literature, our proposed solution is not restricted to antennas that are electrically small. In addition the new formulation can be extended to treat other antennas, such as the T-antenna, the folded unipole antenna, and the loop-loaded monopole antenna. The input impedance, radiation pattern, and gain of the MLD and MLBT antennas are computed and correlated with their parameters. Input impedances of both antennas are computed using NEC. Simple analytical models are presented to compute the radiation patterns of the MLD and the MLBT antennas. For each antenna, a sinusoidal distribution of current is assumed and closed-form expressions for the radiation fields are derived. The results computed using the analytical models are verified by comparing them with the results from the NEC computation. Since in each model the radiation pattern of an antenna is expressed in terms of ready to evaluate algebraic expressions, the computation of such pattern is fast and easy. The input impedance and radiation characteristics of a dual meander antenna are computed using NEC. Similarly as before the input impedance, radiation pattern, and gain of this antenna are also correlated with its parameters. The input impedance and radiation pattern of a planar printed meander antenna are investigated using the Finite-Difference Time-Domain (FDTD) technique. The antenna is modeled on a dielectric substrate both in the presence and absence of a metallic ground plane. Characteristics of the antenna are examined as function of dielectric constant, and substrate thickness. New results of input impedance, radiation pattern, and gain are presented which are vital for the design of such antennas. Several novel applications of self-resonant bent antennas are described. First, a wide-band dual meander-sleeve antenna is designed, manufactured, and measured for application in dual frequency vehicular personal communication. The antenna can operate simultaneously in the 824-894 MHz and 1850-1990 MHz bands of the PCS system. Second, an MLBT dipole is introduced as a feed for plane sheet reflectors. Numerical results computed using NEC show that the feed when used in front of a plane sheet reflector, results in superior radiation characteristics than a conventional dipole feed, namely, it reduces the reflector dimension by 46% for the same front to back ratio, beam width and gain. Finally, a compact plane sheet reflector antenna is described that uses an MLBT monopole feed. Since the antenna uses a monopole, a balun is not required. This antenna has a gain and half-power beam width of 8.4 dBi and 94° respectively. / Graduate

A multiple-antenna-multiple-equalizer (MAME) system is proposed for overcoming cochannel interference (CCI) in code-division multiple access (CDMA) indoor wireless systems. The main advantage of the MAME system is the enhanced interference suppression capability as compared with many existing approaches. Thus, the use of the MAME system can lead to an increase in the capacity of the CDMA system. In the MAME system, a fractionally-spaced equalizer (FSE) is used to process the signal at each antenna. The number of antennas or the tap spacing of the FSEs is not fixed and inherent flexibility is available to the designer. In particular, CDMA indoor wireless systems are best suited to use the interference suppression capabilities of the MAME system. It is shown that spectral correlation present in user signals is the reason for the interference suppression capability of the MAME system. Moreover, the MAME system is interpreted as a dual-domain diversity combiner. Spatial and bandwidth-domain diversity are used and the relative importance of the diversity domains is discussed. These discussions offer new insights into the interference suppression capabilities of the MAME system and give a clear picture of its workings. Extensive simulation results are presented to illustrate the performance of the MAME system under various conditions. Optimal or minimum mean-squared error (MMSE) results are first presented to illustrate the superior interference suppression performance. The effects of the number of antennas, tap spacing, receive filtering, spectral correlation, diversity domains, and near-far conditions on performance are examined and results obtained support the arguments presented earlier in the thesis. The FSEs in the MAME system are implemented as adaptive filters and the mean-squared- error (MSE) performance is investigated. A quasi-Newton (QN) algorithm is recommended over other adaptive filtering algorithms because of ill-conditioning of the autocorrelation matrix in the MAME system. Simulation results confirm the superior convergence performance of the QN algorithm. Decision-directed equalization is also investigated and bit-error rate (BER) results presented illustrate that the gains in the MMSE performance will most likely translate into gains in BER performance. The BER performance in near-far and birth of interferers conditions illustrate that the MAME system is a promising solution to counter these problems. The thesis concludes with an indoor wireless strategy based on the MAME system which offers the following advantages: 1. More users than the processing gain of the CDMA system can share the same bandwidth. 2. No information about code sequences is needed at the receiver. 3. Simple code sequence allocation schemes can be used at the transmitter. 4. Variable numbers of users can be accommodated. 5. Simple power control and error-correction coding schemes can be used. / Graduate

<p>Satellite Look Angles are the coordinates to which an earth station antenna must point to communicate with a satellite. Each satellite has it's own unique set of look angles. The first method, developed to calculate a satellite's look angles, uses standard plane and spherical trigonometry and assumes a perfectly spherical earth. The second method developed is unique to this paper and wi11 not be found anywhere, including general satellite communication textbooks. This method uses a geodetic reference system which refers to the earth as an ellipsoid rather than a sphere. This second method is a more rigorous approach to determining look angles and readily lends itself to pointing at satellites in any given orbit. Fortran code was written implementing both methods and it is concluded that employing a geodetic reference frame is viable where high degrees of accuracy are required. Fortran code was also developed to calculate the pointing angles for Radio Sources such as pulsars and quasars. This code corrects for precession, nutation, annual aberration, and polar motion of the earth.</p> / Master of Science

Thesis: Sc. D., Massachusetts Institute of Technology, Department of Electrical Engineering, 1961. / [1970]. / Cambridge, Mass. / 3 microfiches. / Massachusetts Institute of Technology, Microreproduction Laboratory, / "September 1961." Vita. / Includes bibliographical references (leaves 136-138 ). / by Allan Carter Schell. / Sc. D.