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
Jacob,George; Dr.Mohanan, P(Cochin University of Science & Technology, June , 1998)
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Abstract:
The thesis is the outcome of the experimental and theoretical investigations on a new compact drum-shaped microstrip antenna. A new compact antenna suitable for personal communication system(PCS), Global position System(GPS) and array applications is developed and analysed. The generalised cavity model and spatial fourier transform technique are suitably modified for the analysis of the antenna. The predicted results are compared with experimental results and excellent agreement is observed. The experimental work done by the author in related fields are incorporated as three appendices in this thesis. A single feed dual frequency microstrip antenne is presented in appendix A.Appendix B describes a new broadband dual frequeny microstrip antenna. The bandwidth enhancement effect of microstrip antennas through dielectric resonator loading is demonstarted in Appendix C.
Description:
Department of Electronics,
Cochin University of Science and Technology
Binu, Paul; Dr.Mohanan, P(Cochin University of Science & Technology, September , 2005)
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Abstract:
The thesis explores the outcome of the exhaustive theoretical and experimental investigations performed on Octagonal Microstrip Antenna configurations. Development of the MATLAB TM backed 3D-Conformal Finite Difference Time Domain (CFDTD)Modeller for the numerical computation of the radiation characteristics of the antenna is the theme of the work. The predicted results are verified experimentally and by IE3D TM simulation. The influence of the patch dimensions,feed configurations,feed dimensions and feed positions upon the radiation performance of the antenna is studied in detail. Octagonal Microstrip Antenna configurations suitable for Mobile-Bluetooth application is dealt in detail. A simple design formula for the regular Octagonal geometry is also presented. A compact planar multi band antenna for GPS/DCS/2.4/5.8GHz WLAN application is included as appendix A. Planar near field measurement technique is explained in appendix B.
Description:
Department of Electroncis,
Cochin University of Science and Technology
Sarin, V.P; Dr. K. Vasudevan(Cochin University of Science and Technology, January 14, 2012)
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Abstract:
With the recent progress and rapid increase in mobile terminals, the design of
antennas for small mobile terminals is acquiring great importance. In view of this
situation, several design concepts are already been addressed by the scientists and
engineers. Compactness and efficiency are the major criteria for mobile terminal
antennas. The challenging task of the microwave scientists and engineers is to device
compact printed radiating systems having broadband behavior, together with good
efficiency. Printed antenna technology has received popularity among antenna
scientists after the introduction of microstrip antenna in 1970s. The successors in this
kind such as printed monopoles and planar inverted F are also equally important.
Scientists and Engineers are trying to explore this technology as a viable coast
effective solution for forthcoming microwave revolution. The transmission line
perspectives of antennas are very interesting. The concept behind any
electromagnetic radiator is simple. Any electromagnetic system with a discontinuity
is radiating electromagnetic energy. The size, shape and the orientation of the
discontinuities controls the radiation characteristics of the system such as radiation
pattern, gain, polarization etc. It can be either resonant or non resonant structure.