Numerical analysis of passively loaded and actively reconfigurable plasma monopole antenna using 2-D FDTD method

Abstract

Now a day per person data requirements is looming large. One requires access the large amount of data in a very short period. Therefore development of efficient data network is always being topic of on-going research. Broadband refers to telecommunication system in which a wide band of frequencies is available to transmit information. Because a wide band of frequencies is available, information can be multiplexed and sent on many different frequencies or channels within the band concurrently, allowing more information to be transmitted in a given amount of time. Therefore antenna is plays important role in broadband network for transmission and reception of signals. All available antenna system for communication and data network is worked on limited frequency band. And it is unable to provide the requirement of bandwidth, therefore a development of wider bandwidth frequency antenna is inevitable. Plasma Antenna offers a new solution to the requirement for wider frequency band, which replaces solid metal conductor element with plasma for guiding electromagnetic waves. Basically, plasma is pre-ionized gas contains equal nos. of positive and negative charge particles that's collective effect is neutral. Highly ionized plasma is essentially a good conductor, and therefore plasma filaments can serve as transmission line elements for guiding waves, or antenna surfaces for radiation. The plasma antenna has ability to transmit when the gas is electrified and became stealth when no excitation is provide to gas for further ionization. Therefore it can be “turned off” to make it electrically invisible for the purpose of reducing its scattering signature and eliminating its coupling and interference with other nearby antennas. This peculiar behaviour provides numerous positive points to use plasma antenna as conducting elements in numbers of applications. Simple plasma monopole antenna is numerically simulated and analysis of antenna properties using full wave computational technique i.e. finite difference time domain method (FDTD) in two dimensions with MATLAB software has been presented in detail. Here the far field analysis can be done by considering the magnitude of electric field lying on grids which is located at certain radius R. Radiation characteristic for the monopole has been studied for the variable antenna length and signal frequency which results significant change in radiation parameters like beam-width, radiation intensity, directivity etc. and found as similar to that of metallic antenna. In advance, capacitive loaded plasma monopole antenna is numerically simulated using similar FDTD approach to investigate its radiation characteristics and perspective comparison is done with simulation results of simple plasma monopole. The loaded plasma monopole is defined as a plasma column incorporated with regular structural discontinuity where resultant effect of the discontinuity provides the capacitive loading on antenna element. The study found that the incorporated discontinuity enhances the effective length of antenna and also creates an array effects which improves the radiation parameters of antenna. Further, the same effect can also be achieved in an active manner where external DC magnetic field of certain magnitude has to be applied at specific section of plasma monopole. The study explores that it provides the similar results as obtained in capacitive loaded antenna and also gives an option to online control on radiation pattern which can be reconfigured as desired. To analyse the simulation outcomes in detail, a novel theoretical procedure has been developed. The developed theory found an agreement to the FDTD simulation outcomes.