Design and Development of Reconfigurable Plasma Antenna

Abstract

In this thesis, plasma based reconfigurable antenna and photonic crystal device have been investigated. The first half mainly focused on the design and development of plasma antenna whereas the developed of plasma photonic crystal is presented in second half of the thesis. The research work has been accomplished in many stages which are briefed as follow; Plasma antenna has been developed and investigated for the analysis of its radiation characteristics for variable plasma properties and operating frequencies. In research work, 30cm long plasma column antenna has been experimentally developed at gas pressure, Pr = 0.030mbar and RF power, P0 = 60W atts. The setup is modelled based on the extracted data and simulated for the analysis of resonant frequencies at plasma density (ne) = 2.7×1016m−3 . The radiation patterns at resonant frequencies 112MHz, 347MHz and 409MHz have been investigated experimentally which are found in good agreement with simulation outcomes. The study explores that the radiation patterns show significant change for plasma properties which are the function of gas pressure and power and are more similar like a monopolar radiation pattern. The ability to reconfigure the plasma properties electronically provides an option to online control the radiation characteristics of antenna as per the requirement. Further, an antenna array has been developed by using the classical state of plasma called plasma blobs or striations. This state of plasma inside a column is formed by having critical combination of input parameters where its arrangement is called as collinear array and each blob act as a radiating element. In our experiment, 4 to 6 plasma blobs or striations are formed in 30cm long column for gas pressure Pr = 0.015 − 0.030mbar and power P0 = 40 − 80W atts. Based on the experimental data, the modelling and simulations of two plasma based collinear antenna array having 4 and 5 plasma blobs have been done respectively. The resonant frequencies at 4 and 5 plasma blobs based antenna array having plasma densities, ne = 2.47 × 1016m−3 and 5.85 × 1016m−3 have been investigated. The radiation characteristics at resonant frequencies 56MHz, 73MHz, 178MHz and 390MHz have been experimentally investigated which verify the simulated outcomes. The study explores that the plasma blobs or striations behaving as an antenna array which improves the radiation characteristics in terms of directivity, intensity and beamwidth of radiation in comparison with continues plasma column antenna. In second half, a reconfigurable one-dimensional Single Column Plasma Photonic Crystal (SC-PPC) has been modelled and investigated its Photonic Bandgaps (PBG). The SC-PPC is a novel structure which is simulated for the first time. In our research, SC-PPC is a glass column containing 6 stationary Standing Plasma Density Patterns (SPDP) called plasma blobs created at Pr = 0.035mbar and P0 = 60W atts, where its density varies sinusoidally along the column axis. The plasma density of blobs is measured by using the interferomtry setup. The modelling and simulation of SC-PPC is done for the analysis of PBG at variable plasma density (ne = 1 × 1016m−3 , 5 × 1016m−3 and 9 × 1016m−3 ), shape and size of blobs etc. The simulation results have been investigated which verifies the reconfigurability of SC-PPC. The additional features of SC-PPC over conventional Plasma Photonic Crystal (PPC) are its small in size, tunable lattice constant, and simple structure that can enable wide application scope in various fields ranging from communication to defence. Further, a two dimensional reconfigurable photonic bandgap structure using low-pressure fluorescent tubes has been developed. The model consists of square lattice of 3×3 tubes (60cm long) array placed in free space. The dispersion relation of the PPC has been optimized by using mathematical modelling for the variable plasma density. Modelling of PPC incorporates the actual plasma parameters which have been extracted from the experimental setup, where the variable plasma density is created by changing the applied AC potential in the range of 100 - 240V . The developed PPC is implemented on test bench as per the mathematical modelling outcomes and tested using VNA (Vector Network Analyzer) for investigation of photonic bandgaps in the range of 3 - 7GHz for different plasma densities ranging from 0.4 × 1017m3 - 5.3 × 1017m3 . The main objective of the work is to conceptualize a reliable plasma-based structure for the development of microwave reflectors, filters, absorbers etc. which can have important applications in the field of radar, satellite and navigation.