Design of Ku- and Ka-Band Flat Dual Circular Polarized Reflectarrays by Combining Variable Rotation Technique and Element Size Variation

Rafael Florencio,Eduardo Martinez-De-Rioja,Vicente Losada,Jose A Encinar,Daniel Martinez-De-Rioja,Rafael R Boix

doi:10.3390/electronics9060985

Abstract

In this work circularly polarized flat reflectarray antennas are designed to work at downlink frequencies in Ku- and Ka-band. The design approach for circular polarization radiation combines both the variable rotation technique (VRT) and the element size variation technique (ESVT). The reflectarray element employed consists of a rotable split ring operating at 12 GHz (Ku-band) that surrounds two orthogonal sets of parallel dipoles of variable size operating at 20 GHz (Ka-band). Rotations of split rings and different sizes of dipoles are exploited as degrees of freedom by VRT and ESVT for designing focused beams dual band dual circular polarized reflectarrays. The split ring can be used to achieve single focused beams for circular polarization by VRT at 12 GHz, and the set of orthogonal dipoles can be used to achieve two focused beams for dual circular polarization by ESVT at 20 GHz. In this way, the reflectarray element has been used to design two flat dual band circularly polarized reflectarrays that generate three pencil beams either in the same direction or in different directions: one pencil beam with right-hand circular polarization (RHCP) at 12 GHz and two pencil beams with both RHCP and left-hand circular polarization (LHCP) at 20 GHz. The designed reflectarrays are carried out under local periodicity assumption by means of in-house electromagnetic software that applies the Method of Moments in the Spectral Domain. Validations of the in-house electromagnetic software show significant CPU time savings with respect to CPU time consumption provided by commercial software of general purpose as CST electromagnetics software. Numerical results of radiation patterns produced by the designed reflectarrays show efficiencies around 65% and a bandwidth of 6% for a main beam cross-polarization discrimination of 25 dB. The numerical results are satisfactorily validated by CST software and a tolerance errors study has been numerically carried out with acceptable results.

Highlights

For satcom-on-the-move (SOTM) applications, there is an increasing interest in developing Kuand Ka-band antennas that share a single aperture
In this work we focus on the design of a circular polarization reflectarray antenna operating at
In [18] this element was used to show the feasibility of a reflectarray design for the separation of two unfocused beams in dual-band for orthogonal circular polarizations by means of variable rotation technique (VRT) using a single feeder

Summary

Introduction

For satcom-on-the-move (SOTM) applications, there is an increasing interest in developing Kuand Ka-band antennas that share a single aperture. In [18] this element was used to show the feasibility of a reflectarray design for the separation of two unfocused beams in dual-band for orthogonal circular polarizations by means of VRT using a single feeder. The mean novelty of this work shows that both the rotations of split rings and the different sizes of dipoles are exploited as degrees of freedom by VRT and ESVT for designing focused beams dual band dual circular polarized reflectarrays for Ku- and Ka-band satellite downlink applications. Each designed antenna provides single circular polarization radiation at 12 GHz by variable rotation capability of the element, and dual circular polarization radiation at 20 GHz by variable size capability of the element, either in the same beam direction at both frequencies or in different beam directions. Such promising results suggest that proposed architecture could be applied for 5G and beyond applications3 [19]

Reflectarray

and Results

20 GHz both

10. The results elevation of radiation the radiation patterns are shown in Figure

12 GHz but a significant increment of cross-polar is of the copolar at pattern

Conclusions