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Interest of Micro-Electromechanical System (MEMS) antennas in Terahertz (THz) applications has rapidly expanded in recent years due to the advent of accurate Computer Aided Design (CAD) tools. The very special needs of newly proposed MEMS antennas, especially with a wide bandwidth range, require advanced optimization procedures of enhancing already established designs. This paper provides a compact design of a wideband MEMS helix antenna optimized using tree-dimensional High Frequency Structure Simulator (3D-HFSS) based on Quasi-Newton (Q-N) and Sequential Non Linear Programming (SNLP) techniques to modify the antenna structure with a high accuracy for the selective band of frequencies by training the samples and minimizing the error from Finite Element Method-(FEM) based simulation tool. The helix antenna is presented using MEMS technology and shows high performance demonstrated by very low return losses of less than -20 to -65 dB for a wide range of frequencies from 2.5 to 5 THz. High antenna geometry precision and efficient performance are finally achieved by rectifying and synthesizing various tunable parameters embedded in silicon substrate including both helix form and feeding line parameters. [ABSTRACT FROM AUTHOR]

Here we propose the use of twist and glide symmetries to increase the equivalent refractive index in a helical guiding structure. Twist- and glide-symmetrical distributions are created with corrugations placed at both sides of a helical strip. Combined twist-and glide-symmetrical helical unit cells are studied in terms of their constituent parameters. The increase of the propagation constant is mainly controlled by the length of the corrugations. In our proposed helix antenna, twist and glide symmetry cells are used to reduce significantly the operational frequency compared with conventional helix antenna. Equivalently, for a given frequency of operation, the dimensions of helix are reduced with the use of higher symmetries. The theoretical results obtained for our proposed helical structure based on higher symmetries show a reduction of 42.2% in the antenna size maintaining a similar antenna performance when compared to conventional helix antennas.

A slot helix antenna working in Global Positioning System (GPS) L1 and L2 bands is proposed in this paper. Adopting sequential rotation technique, the proposed antenna is equipped with six helix radiation arms and fed by a microstrip line with folded shape. The whole antenna can be built on a full printed circuit board; so, it is easy to process the proposed antenna. The circularly polarized radiation mechanism of a circular array is analyzed in a new perspective to guide the design. A double-faced slot radiation structure is also established for dual-band operation. Additionally, a traveling wave feeding network suitable for the proposed antenna is presented. The experimental results show that the proposed antenna has good properties in GPS L1 and L2 bands. [ABSTRACT FROM PUBLISHER]

This communication proposes the design of a quadrifilar helix antenna (QHA) with stepped-width arms and a meander feeding network. The stepped-width arms are applied to reduce the antenna size and adjust the frequency interval for dual-band operation. The feeding network includes a 90°-hybrid chip coupler and two meander lines that are designed to give a 180°-phase delay. The proposed QHA is optimized using a genetic algorithm (GA) and then fabricated to measure its performances in a full anechoic chamber. The results demonstrate that the proposed antenna is suitable to be used for dual-band global positioning system (GPS) applications. [ABSTRACT FROM PUBLISHER]

The bandwidth of a resonant quadrifilar helix antenna (QHA) is shown to be strongly dependent on the design of the feed network. In this paper, we compare the impedance and radiation-pattern performance of two QHAs driven by different feed arrangements. A qualitative explanation for the difference in the behaviour of the antenna is given by observing the amplitude and phase distribution of the current in the helices. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 11–15, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20886 [ABSTRACT FROM AUTHOR]

In this paper, different methods for measuring the input impedance of a quadrifilar helix (QFH) antenna are presented along with the underlying physical theory. Shortcomings of the known slotted line method are discussed. New practical and efficient ways of the input impedance derivation based on S-parameters measured at the antenna input ports are introduced. A QFH input impedance is measured with different schemes, and the obtained results are compared and discussed. Finally, the results are concluded. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 102–107, 1998. [ABSTRACT FROM AUTHOR]