Following the reported detection of an absorption profile associated with the 21[Formula: see text]cm sky-averaged signal from the Cosmic Dawn by the EDGES experiment in 2018, a number of experiments have been set up to verify this result. This paper discusses the design process used for global 21[Formula: see text]cm experiments, focusing specifically on the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH). This experiment will seek to understand and compensate for systematic errors present using detailed modeling and characterization of the instrumentation. Detailed quantitative figures of merit and numerical modeling are used to assist the design process of the REACH dipole antenna (one of the two antenna designs for REACH Phase I). This design process produced a 2.5:1 frequency bandwidth dipole. The aim of this design was to balance spectral smoothness and low impedance reflections with the ability to describe and understand the antenna response to the sky signal to inform the critically important calibration during observation and data analysis. 

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Radio Antenna Design for Sky-Averaged 21cm Cosmology Experiments: The REACH Case

Wideband, wide-scan antenna arrays are a promising candidate for the future wireless networks and as well as an essential part of experimental radio astrophysics. Understanding the underline physic ...

Next Generation Wideband Antenna Arrays for Communications and Radio Astrophysics

In this work the focus is on the impact of edge effects in the equilateral triangular lattice of a strongly coupled dipole antenna array. A novel wideband strongly coupled, single polarized, dipole ...

Edge effects in a strongly coupled dipole element array in triangular lattice

The present invention relates to a single polarized radiator (40) comprising a plurality of planar notch radiating elements (41) arranged on a dielectric substrate (22). Each notch radiating element (41) comprises: a metallized region (23) on a first side of the dielectric substrate (22) extending across the width (w) of the notch radiating element from a forward edge (24) of the notch radiating element (41) to a rear edge (25) of the notch radiating element (41), a tuning element (26) in the metallized region (23) adjacent to a feeding point of the notch radiating element (41), a notch (28) extending from the tuning element (26) to the forward edge (24) of the notch radiating element (41) thereby creating a notch profile (29), and a plurality of indentations (42) in the metallized region (23) along each side of the notch (28) to extend the length of the notch profile (29).

A broadband antenna

A novel method of reducing the size of a conventional dipole antenna is introduced by means of replacing one of the dipole arms with a helical element. The result of this asymmetrical arrangement is an antenna that presents an omnidirectional pattern with a modest reduction in gain and bandwidth, in comparison to a symmetrical dipole antenna. The structure is effectively represented as a helically counter-poised monopole. It is shown that the counter-poised helix for the monopole, effectively replaces the ground plane of a conventional monopole antenna, or alternatively by using this method the antennas size can be significantly reduced from a full dipole. The principle is validated through measurement of return loss, antenna gain and cross-polarization level.

http://ieeexplore.ieee.org/iel7/7604848/7738091/07738148.pdf

Helically counter-poised monopole antenna

The scope of this work is to investigate asymmetry in a strongly coupled dipole array and exploit its effect for bandwidth and scanning improvement. Typically, antenna array elements are symmetrical in E-and H-plane. Introducing non-symmetric elements offers additional freedom to improve the array characteristics. The effect of non-symmetric elements is studied and a reference case is created with a symmetric element in unit cell design. The obtained bandwidth for the reference case is a 6:1 at the broadside. Using this element as a base for this work, we pixelate parts of the element and optimize this parts with a genetic algorithm. Having an initial design (solution) reduces significant the number of iterations needed for the genetic algorithm to converge. The element was studied in a rectangular and in triangular lattice. The results indicate that in both cases the performance is improved. Finally, the performance of the developed array element was investigated in terms of the array figure of merit, a general measure of array element performance. This resulted in the best known array figure of merit; 0.84.

A. Stjerman

Papers

Exploiting asymmetry in a capacitively loaded strongly coupled dipole array