Nishamol, M S; Dr.Vasudevan, K(Cochin University of Science and Technology, January 4, 2012)
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Abstract:
Antennas are necessary and vital components of communication and radar systems, but sometimes their inability to adjust to new operating scenarios can limit system performance. Reconfigurable antennas can adjust with changing system requirements or environmental conditions and provide additional levels of functionality that may result in wider instantaneous frequency bandwidths, more
extensive scan volumes, and radiation patterns with more desirable side lobe distributions. Their agility and diversity created new horizons for different types of applications especially in cognitive radio, Multiple Input Multiple Output Systems, satellites and many other applications. Reconfigurable antennas satisfy the requirements for increased functionality, such as direction finding, beam steering,
radar, control and command, within a confined volume. The intelligence associated with the reconfigurable antennas revolved around switching mechanisms utilized. In the present work, we have investigated frequency reconfigurable polarization diversity antennas using two methods: 1. By using low-loss, high-isolation switches such as PIN diode, the antenna can be structurally reconfigured to maintain the elements near their resonant dimensions for different frequency bands and/or polarization.
2. Secondly, the incorporation of variable capacitors or varactors, to overcome many problems faced in using switches and their biasing. The performances of these designs have been studied using standard simulation tools used in industry/academia and they have been experimentally verified. Antenna design guidelines are also deduced by accounting the resonances. One of the major contributions of the thesis lies in the analysis of the designed antennas using FDTD based numerical computation to validate their performance.
Description:
Department of Electronics, Cochin University of Science and Technology
Laila, D; Dr.Mohanan, P(Cochin University of Science And Technology, October , 2012)
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Abstract:
Antennas, the key element in wireless communication devices had
undergone amazing developments especially in the direction of compactness
and safety aspects. In the last two decades, the use of the cellular phones has
become the most popular mode of communication across the globe. At the same
time, the concerns about the radiation effects have increased in the general
public. The main concern of this thesis is to develop a mobile antenna which
gives reduced RF interference to the user. The reduction of the power absorbed
by the user can tremendously avoid any possible health hazards.
The radiation characteristic of a monopole antenna is modified with good
radiation characteristics suitable for a mobile handset. The modification is
implemented by using different resonating structures which provides reduced
radiation along one direction. The direction of less radiation can be changed by
modifying the planar antenna structure to a ground folded antenna. This
modified structure with excellent radiation characteristic is suitable for modern
wireless handheld devices with less user RF interference. Specific Absorption
Rate (SAR) is an important parameter for mobile handset. The SAR is
estimated for the newly developed antenna for different conditions and
discussed in this thesis.
Description:
Department of Electronics, Cochin University of Science And Technology