Reconfigurable Antennas Based on Plasma Reflectors and Cylindrical Slotted Waveguide

In this chapter, we focus on the application of plasma structures to realize reconfigurable antennas. Several approaches are presented to dynamically control the beamwidth and radiation gain of circularly polarized helical antennas based on plasma reflectors. Ideas and design principles were discussed and confirmed by full-wave simulations and measurements of realized prototypes. It is shown that plasma reflectors can be effectively used to design reconfigurable helicone antennas with controllable gain and beamwidth. The chapter also presents a reconfigurable slotted antenna using a plasma tube inside the metallic waveguide. It is shown that the radiation pattern of the antenna can be readily reconfigured by changing the state of the plasma column. In short, it is shown that in contrast to conventional methods based on electronic or mechanical devices, reconfigurable antennas based on plasma media benefit from simple and relatively low-cost structures as well as high performance

The effect of motion formation on cooperative navigation

The effect of formation movement on the performance of cooperative navigation is investigated in this paper. First, the inertial navigation system of each agent with a certain accuracy is modeled and simulated. Initial results showed that the navigation error of each agent increased individually over time, and this problem is more severe for agents equipped with a weaker system. Cooperative navigation is implemented for the agents to resolve this problem. It is shown that the total navigation errors are improved by observing and participating the relative distance between the agents. Various simulations and experimental tests using two real agents supported this assertation. The performance of cooperative navigation can be improved further through appropriate formation. Proper formations are investigated and evaluated through simulations. The collective covariance matrix is employed to form an objective function using an extended Kalman filter (EKF). This function has been minimized using Newton’s method, which could be the solution for the formation. The simulation results show that better accuracy can be achieved by applying the optimal formation trajectory

Design of an axial mode helical antenna with buffer layer for underwater applications

Recently, there is an increasing demand for high-speed wireless communication network for short-range underwater communication. From previous research, most underwater antennas produced omnidirectional radiation pattern which has lower antenna gain. There are a few considerations that need to be taken if the antenna is designed to operate in water environment. This paper discusses the electromagnetic properties which affect the underwater antenna design. Physical properties such as electrical permittivity and conductivity of water contribute significant effect to the size of the antenna as it influences the behavior of electromagnetic signal that propagates in water. In this study, an axial mode helical antenna with waterproof container is presented which operates at 433 MHz. The axial mode helical antenna has circular polarization and is suitable to support wireless application which is surrounded by some obstruction. The proposed antenna produces a bidirectional radiation pattern by placing it into a waterproof casing. Good agreement between the simulation and measurement results validates the concept. However, a little discrepancy between the simulated and measured results may be attributed to the noise originated from the equipment and the environment

Beam-Steerable Helical Antenna Using Plasma Reflectors

International audienceThe aim of this paper is to investigate the steering mechanism of the beam pattern of a helical antenna using a half-cup plasma reflector. To this end, variations of the radiation characteristics and also the direction of the main beam of the antenna due to changes in the dimensions of the half-cup plasma reflector, including its diameter and height, are numerically computed and analyzed. The simulation results show that using this structure, the beam direction can be altered in 3-D space within a solid angle of +/- 10 degrees. Also, it is highlighted that the half-cup plasma reflector may adversely affect the polarization of the helical antenna. Therefore, a trade-off between polarization and performance of an antenna based on a parametric study has to be made. Thus, in this investigation, the axial ratio of the antenna is also analyzed for each dimension. For demonstration, the study is used for the design of a circularly polarized helical antenna with a half-cup plasma reflector. Good agreement between the numerically calculated and measured results validates the presented study

Tunable Rectangular Waveguide Bandpass Filter Based on Plasma Technology

International audienceThis paper presents a novel tunable bandpass filter that exploits plasma conductors within a standard hollow waveguide framework. The operational principle of the filter leverages the reconfigurability of plasma and its tunable properties, allowing dynamic control over the lower frequency boundary. Through the adjustment of plasma frequency, the filter demonstrates remarkable adaptability, shifting the lower cutoff frequency within a range from 1.66 GHz to 1.75 GHz while maintaining a nearly fixed upper cutoff frequency at approximately 2 GHz. Additionally, the paper includes a parametric analysis that investigates the influence of post dimensions on filter performance. This analysis underscores the significance of initial post dimensions in shaping the bandwidth of the filter. Findings affirm the feasibility of this innovative filter concept

Reconfigurable biconcave lens antenna based on plasma technology

Abstract This article is focused on the application of plasma technology for the development of microwave lens antennas with electronically controllable radiation gain. With this aim, the analytical background and design procedure for designing a biconcave lens based on plasma dielectric material are presented. The procedure is used to design a plasma lens antenna with a pyramidal horn feed. The effect of switching the designed lens ON and OFF on the radiation gain of the lens antenna is investigated. It is also shown that the plasma frequency of the lens can be used to dynamically adjust the radiation gain. A one-dimensional version of the proposed plasma lens operating at 10 GHz has been developed to validate the concept. Experimentally measured characteristics of a fabricated prototype of the lens antenna based on commercially available fluorescent lamps confirm the presented design procedure and numerical results. The results also show that changing the plasma frequency of the lens can be used to adjust the radiation gain of the proposed lens antenna

Design of an axial mode helical antenna with buffer layer for underwater applications

Recently, there is an increasing demand for high-speed wireless communication network for short-range underwater communication. From previous research, most underwater antennas produced omnidirectional radiation pattern which has lower antenna gain. There are a few considerations that need to be taken if the antenna is designed to operate in water environment. This paper discusses the electromagnetic properties which affect the underwater antenna design. Physical properties such as electrical permittivity and conductivity of water contribute significant effect to the size of the antenna as it influences the behavior of electromagnetic signal that propagates in water. In this study, an axial mode helical antenna with waterproof container is presented which operates at 433 MHz. The axial mode helical antenna has circular polarization and is suitable to support wireless application which is surrounded by some obstruction. The proposed antenna produces a bidirectional radiation pattern by placing it into a waterproof casing. Good agreement between the simulation and measurement results validates the concept. However, a little discrepancy between the simulated and measured results may be attributed to the noise originated from the equipment and the environment