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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

C-Band TM Smart Antenna

Ryken, Marv 10 1900 (has links)
ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / This paper addresses the system requirements of the C-Band TM antenna that will take the place of the S-Band TM antenna used in applications on munitions and targets that require a quasi-omni directional antenna pattern. For these applications, the C-Band TM effective radiated power (ERP) must be approximately 3 dB higher than the S-Band TM ERP to achieve the same system performance due mainly to weather and environmental differences. From a systems stand-point, this will be a problem for the following reasons: power amplification at higher frequencies is usually less efficient, there is a limit on prime power due to battery capabilities, and a more complex corporate feed at C-Band as compared to S-Band will produce more loss. This means that a more fruitful approach would be to use smart antenna ideas to achieve the required higher ERP as compared to current approaches of using higher power transistors and more battery power. Several smart antenna ideas are introduced in this paper, switchable driven element antenna is described including active amplification at each element.
2

The Stub Loaded Helix: A Reduced Size Helical Antenna

Barts, Robert Michael 08 December 2003 (has links)
This dissertation details the development of a novel reduced size axial mode helical antenna called the Stub Loaded Helix (SLH). The SLH achieves a significant reduction in helix size, both diameter and length, compared to the conventional axial mode helix antenna with only small compromises in performance. The SLH achieves this entirely through the use of a unique geometry. The performance characteristics of the SLH are explored through the use of computer simulations using NEC (Numerical Electromagnetics Code) to study the effects of design parameter variations. Based on those simulations, design guides are developed. The numerical simulations are verified though measurements of experimental prototypes. The program of experimental prototypes included the development of an appropriate impedance matching network for the SLH, which is also detailed. / Ph. D.
3

Antenna Design for Portable Applications in LTE Band

Islam, Jahurul January 2011 (has links)
The planar dual band monopole antenna is presented in this project report for Long Term Evolution (LTE). The proposed planar monopole antenna is selected because of its simple structure, cost effective components and excellent performance. The antenna operates in 3.4 GHz to 3.6 GHz and 3.6 GHz to 3.8 GHz in desired LTE frequency band. The frequency bands 3.4- 3.6 GHz and 3.6- 3.8 GHz are already available as a study of current plan according to UMTS and LTE   systems.   The designed antenna works parallel with the LTE radio access; packet core networks are also involved. A very well developed and good designed antenna relaxes the other system components and improves the performances of the whole system. For the portable application and for the multiband scenario, planar monopole is the best candidate for the proposed two bands. LTE (3.4 GHz-3.6 GHz) and LTE-Advanced (3.6 GHz-3.8 GHz) antennas are designed for portable wireless devices. Radiation pattern and operating frequency are varied according to feeding of antenna.  Return loss, radiation pattern, antenna efficiency, bandwidth and gain are important parameters of the designed antenna and are measured after simulation through CST Microwave Studio. The designed antenna is then fabricated in KTH antenna Lab.
4

FDTD Analysis of Metamaterial Coated Microwave Antenna

Cholleti, Vipin K. 2010 May 1900 (has links)
Due to the growth in mobile wireless systems, electrically small antennas (ESAs) which are efficient and have significant bandwidth are in great demand. But these requirements are contradictory. ESAs are known to be highly capacitive in nature. As a result of this, matching a power source to the ESA requires a matching network which increases the cost in terms of manufacturing as well as real estate. In recent years a new class of materials called metamaterials has emerged. These manmade materials with their unusual constitutive parameters possess immense potential to solve the problem of size reduction. This study seeks to validate, using Finite Difference Time Domain (FDTD) technique, a new metamaterial construct to achieve the desired objectives. FDTD code is developed for a cylindrical metamaterial wrapped around a modified biological antenna. The metamaterials are modeled using a Drude constitutive parameter model to simulate frequency dispersion. Epsilon Negative (ENG) as well as Double Negative (DNG) metamaterials are taken into consideration. Results show that the ESA using a metamaterial wraparound is found to have a quality factor lower than the theoretical Chu limit. Both ENG as well as DNG metamaterials exhibit their potential. The resonant frequency of the metamaterial antenna is reduced over the classical design while the radiation pattern of the antenna remains virtually unchanged.
5

NOVEL ANTENNA DESIGNS FOR A PCMCIA CARD

Chen, Yen-Yu 20 June 2003 (has links)
In this thesis, two novel antennas and three advanced design concepts for further studies are presented. Firstly, the design of diversity dual-band inverted-F monopole antenna using two back-to-back stacked metallic strips for operating in the 2.4 and 5.2 GHz WLAN band is presented. Secondly, the diversity dual-band inverted-F monopole antenna mounted vertically at the edge of a system circuit board is studied. Finally, three advanced design concepts are discussed to demonstrate the methods of controlling radiation patterns to achieve better radiation characteristics of the antenna.
6

Antenna array processing in wireless communications and radar systems /

Lin, Xiaotong, January 2000 (has links)
Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 146-147).
7

Antenna Performance Software

Yousefi, Erfan, Farhat, Nasrin January 2013 (has links)
Antenna performance software is a tool to measure the quality and enactment of the newly developed products. This is an important matter to the development department of the company since the products must be verified to work with regarding to the user specifications. Using LabView, this tool has been developed in order to provide ease for this test. This software has been compared with previous solutions given and has been optimized to be able to do the tests successfully.
8

Trade-offs of Antenna Fabrication Techniques

Ryken, Marv 10 1900 (has links)
ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / This paper addresses the future military munitions' system requirements for antennas in terms of the existing versus new fabrication technology. The antenna requirements of the future smart munitions will be GPS for precision guidance and TM for system performance testing. The environmental requirements remain the same; large temperature operating range with operation at high temperatures and high shock capable. As usual, the munitions are getting smaller, frequency bandwidth is getting larger, and the cost of the antennas must be minimized in production quantities. In particular this paper compares the existing antenna fabrication technology of Teflon based dielectric printed circuits versus multilayer alumina in the green state, a technology that has been perfected for fabricating microwave integrated circuits (MIC's). The trade-offs that will be addressed are temperature, shock, cost, tunability, loss, size, dielectric constant, and frequency bandwidth. There has been a significant effort to miniaturize the GPS and TM antenna using higher dielectric constant materials. The most popular direction of this effort has been to use ceramic impregnated Teflon. The ultimate temperature performance is the material with a dielectric constant around 2 since this material exhibits a very low coefficient of change with temperature. Materials are available with nominal dielectric constants of 6 and 10 to reduce the size of the antenna but the coefficient of change with temperature is very large and leaves these materials marginal for military temperature ranges. There have also been two other problems with Teflon based printed circuit boards, forming and bonding the boards in a 3D shape and homogeneity of the dielectric constant in the board and after bonding. These problems usually make tuning a requirement and drive the cost of antenna fabrication up. There has been a revolution in MIC's. The circuits are now being made with multiple layers of ceramic (alumina) with interlayer conductive connections and a nominal dielectric constant of 10. The layers are formed in the green state and fired at high temperature and the resulting alumina substrate has a very low coefficient of change with temperature and low loss. Since this procedure is now beyond development, the cost is low and the volume capability is high. Another significant point is that the part can be any shape since the substrate is done in the green state (formable) and then fired.
9

Robust minimum variance beamforming with multiple response constraints

Robinson, Michael, 1982- January 2007 (has links)
Conventional beamformers can be sensitive to mismatches between presumed and actual steering vectors of the signal-of-interest. A recently proposed class of robust beamformers aim to counteract this problem by using a non-attenuation constraint inside a single hypersphere centered at the presumed steering vector of the signal-of-interest. In an effort to strike a balance between robustness to steering vector error and interference-plus-noise suppression, we propose in this manuscript to use multiple concentric hyperspheres instead of one with different degrees of protection in each. We derive several useful properties of this multiply constrained beamformer and use numerical simulations to show that using two constraints yields improved signal-to-interference-plus-noise-ratio compared to one constraint in certain scenarios, particularly at a large input signal-to-noise-ratio. / The manuscript also includes an overview of conventional beamforming, the mismatch problem and previously proposed robust beamformers.
10

Array pattern synthesis and hardware realisation for active communication arrays.

Lange, Volker Wolfgang. January 1969 (has links) (PDF)
Thesis (M.E. 1971) from the Faculty of Engineering, University of Adelaide.

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