Theoretical Investigation of Radiation in the Normal Direction for a Metaloop Antenna

Hisamatsu Nakano,Junji Yamauchi,Tomoki Abe

doi:10.1109/access.2020.3007505

Hisamatsu Nakano, Junji Yamauchi + Show 1 more

Open Access

https://doi.org/10.1109/access.2020.3007505

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Abstract

Radiation in the normal direction for a metaloop antenna is discussed. First, the radiation field generated from an N-type current distributed along a loop, E N , is investigated. The investigation clarifies the behavior of the unbalance between the left-handed circularly polarized (LHCP) component of E N at frequency f (-) and the right-handed circularly polarized (RHCP) component of EN at frequency f (+) , where the loop circumference at these frequencies is one guided wavelength. Secondly, the radiation field generated from a C-type current, E C , is investigated. The second investigation, when combined with the first investigation, leads to an inference that balanced radiation (and hence balanced gain) will be obtained when the N-type current over a certain region of the loop is replaced with a C-type current. Thirdly, to check this inference, a radiation field generated from a composite of the N-type and C-type currents, E NC , is formulated. Using this formulation, the ratio of the gain for an LHCP wave to the gain for an RHCP wave, G r , is derived. Fourthly, a metaloop antenna simulation model that has a balanced gain is created using practical N-type and C-type metaatoms that realize the composite current. Finally, a metaloop antenna is fabricated on the basis of the antenna simulation model. Measurements confirm that the fabricated metaloop antenna has a balanced gain in the normal direction. As supplementary data, the radiation pattern and VSWR of the fabricated metaloop antenna are also presented, together with the radiation efficiency and some comments.

Highlights

Polarized (CP) antennas have been used, for example, in satellite communications and mobile communications and offer the advantage that polarization alignment of the transmitting and receiving antennas is not needed
As will be clarified in this paper, the metaloop antenna has the drawback that the maximum intensity of the left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) radiation fields in the direction normal to the loop plane is generally not the same, and the gain of the Du-BND Cnt-Circularly polarized (CP) radiation in the normal direction is unbalanced
This paper resolves the issue of unbalanced radiation field intensities in the normal direction for the metaloop antenna that is encountered with Du-BND counter circularly polarized (Cnt-CP) radiation

Summary

INTRODUCTION

Polarized (CP) antennas have been used, for example, in satellite communications and mobile communications and offer the advantage that polarization alignment of the transmitting and receiving antennas is not needed. As will be clarified in this paper, the metaloop antenna has the drawback that the maximum intensity of the LHCP and RHCP radiation fields in the direction normal to the loop plane is generally not the same, and the gain of the Du-BND Cnt-CP radiation in the normal direction is unbalanced. This paper resolves the issue of unbalanced radiation field intensities (and gains) in the normal direction for the metaloop antenna that is encountered with Du-BND Cnt-CP radiation. Based on an insight into these radiation fields, an innovative metaloop antenna with a balanced gain is created. It is worthy to describe that the determination of Ns in this paper is theoretically performed on the basis of newly derived equations and an insight into them; in addition, experiment validates a balanced gain for the NC-type metaloop antenna with determined Ns for the first time.

RADIATION FROM AN N-TYPE CURRENT IN THE

POLARIZATION FACTOR q AND UNBALANCED

Findings

CONCLUSIONS