A dielectric free near field phase transforming structure for wideband gain enhancement of antennas

Foez Ahmed; Muhammad U Afzal; Touseef Hayat; Karu P Esselle; Dushmantha N Thalakotuna

doi:10.1038/s41598-021-93975-2

A dielectric free near field phase transforming structure for wideband gain enhancement of antennas

Sci Rep. 2021 Jul 28;11(1):14613. doi: 10.1038/s41598-021-93975-2.

Authors

Foez Ahmed¹, Muhammad U Afzal², Touseef Hayat³, Karu P Esselle², Dushmantha N Thalakotuna²

Affiliations

¹ School of Electrical and Data Engineering, University of Technology Sydney (UTS), Sydney, NSW, 2007, Australia. Foez.Ahmed@student.uts.edu.au.
² School of Electrical and Data Engineering, University of Technology Sydney (UTS), Sydney, NSW, 2007, Australia.
³ School of Engineering, Macquarie University, Sydney, NSW, 2109, Australia.

Abstract

The gain of some aperture antennas can be significantly increased by making the antenna near-field phase distribution more uniform, using a phase-transformation structure. A novel dielectric-free phase transforming structure (DF-PTS) is presented in this paper for this purpose, and its ability to correct the aperture phase distribution of a resonant cavity antenna (RCA) over a much wider bandwidth is demonstrated. As opposed to printed multilayered metasurfaces, all the cells in crucial locations of the DF-PTS have a phase response that tracks the phase error of the RCA over a large bandwidth, and in addition have wideband transmission characteristics, resulting in a wideband antenna system. The new DF-PTS, made of three thin metal sheets each containing modified-eight-arm-asterisk-shaped slots, is significantly stronger than the previous DF-PTS, which requires thin and long metal interconnects between metal patches. The third advantage of the new DF-PTS is, all phase transformation cells in it are highly transparent, each with a transmission magnitude greater than - 1 dB at the design frequency, ensuring excellent phase correction with minimal effect on aperture amplitude distribution. With the DF-PTS, RCA gain increases to 20.1 dBi, which is significantly greater than its 10.7 dBi gain without the DF-PTS. The measured 10-dB return loss bandwidth and the 3-dB gain bandwidth of the RCA with DF-PTS are 46% and 12%, respectively.