High-Efficiency Polarizer Reflectarray Antennas for Data Transmission Links from a CubeSat

Round 1

Reviewer 1 Report

The paper presents two innovative design of high-efficiency polarizer reflectarray antennas for CubeSat applications. The paper is clear and well written, and the innovative contribution is discussed and supported by the reported results which include both numerical and experimental validations with excellent agreement. The achieved aperture efficiencies and overall performance of the designed layouts demonstrate the validity of the proposed concept. I recommend the publication of the work after the following minor issues are addressed.

• please comment on the choice of a two-layer stacked patch geometry for the first reflectarray unit cell (e.g., why a single layer rectangular patch layout was considered not adequate for the specific scenario?)
• for the sake of completeness, please comment on the choice of the substrate material and on the dielectric properties (permittivity, losses)  that have been employed in the MoM analysis with reference to the CuClad. Moreover, does the MoM model considers finite conductivity for copper parts?

Author Response

Reviewer 1. Comments:

The paper presents two innovative design of high-efficiency polarizer reflectarray antennas for CubeSat applications. The paper is clear and well written, and the innovative contribution is discussed and supported by the reported results which include both numerical and experimental validations with excellent agreement. The achieved aperture efficiencies and overall performance of the designed layouts demonstrate the validity of the proposed concept. I recommend the publication of the work after the following minor issues are addressed.

1.       Please comment on the choice of a two-layer stacked patch geometry for the first reflectarray unit cell (e.g., why a single layer rectangular patch layout was considered not adequate for the specific scenario?).

Answer: The use of two stacked patches instead of one patch provides a larger phase variation range (around 500°) with a smooth slope of the phase curves, as can be checked in Figs. 5(a) and 5(b). These characteristics result in a broadband performance of the reflectarray antenna, as it is shown in Figs. 9 and 10. Also, the smooth slope of the phase curves makes easier the design of the elements and reduces the phases errors that may be produced by manufacturing tolerances. Using a single patch leads to a smaller phase variation range (around 300°) and a steep slope of the phase curves, as shown in the supporting reference [R1], which results in a narrowband performance of the antenna. Alternatively, single-layer multi-resonant reflectarray cells based on 3 parallel dipoles for each polarization [R2], as shown in Fig. 13, could be used for a single frequency band.  Note that many single-layer reflectarray cells [R3, R4] have two-planes of symmetry and does not allow a different phase-shift of 90 between the two field components.

This information has been included in the revised manuscript in page 2, lines 78-80, and in page 3, lines 109-111. The supporting references [R3, R4, R1] have been added to the reference list as [22, 23, 24].

[R1] Encinar, J. A. Design of two-layer printed reflectarrays using patches of variable size. IEEE Trans. Antennas Propag., 2001, vol. 49, no. 10, pp. 1403-1410.

[R2] Florencio, R.; Boix, R. R.; Losada, V.; Encinar, J. A.; Carrasco, E.; Arrebola, M. Comparative study of reflectarrays based on cells with three coplanar dipoles and reflectarrays based on cells with three stacked patches, Proc. 6th European Conf. Antennas Propag., 2012, pp. 3707-3710

[R3] Chaharmir, M. R.; Shaker, J.; Legay, H. Broadband Design of a Single Layer Large Reflectarray Using Multi Cross Loop Elements. IEEE Trans Antennas Propag., 2009, vol. 57, no. 10, pp. 3363-3366.

[R4] Hasani, H.; Peixeiro, C.; Skrivervik, A.; Perruisseau-Carrier, J. Single-layer quad-band printed reflectarray antenna with dual linear polarization, IEEE Trans. Antennas Propag., 2015, vol. 63, no. 12, pp. 5522-5528.

 2.       For the sake of completeness, please comment on the choice of the substrate material and on the dielectric properties (permittivity, losses)  that have been employed in the MoM analysis with reference to the CuClad. Moreover, does the MoM model considers finite conductivity for copper parts?

Answer: The two dielectric layers are implemented by CuClad 233LX substrates, each with thickness h = 0.787 mm, relative dielectric constant of 2.33, and loss tangent of 0.0012. These substrates are commercially available materials, which have been chosen because of their simplicity of manufacturing and low losses. The two substrates have been bonded by using a commercial 37-μm CuClad 6250 bonding film (relative dielectric constant of 2.32, and loss tangent of 0.0013).

For the MoM simulations, we have considered the relative dielectric constant and loss tangent of each dielectric layer, while the printed elements are modelled as perfect conductors (infinite conductivity). The simulations account for the dielectric losses of the substrates; the conductivity losses of the copper are negligible at these frequencies.

This information has been included in the revised manuscript in page 3, lines 116-117, and also in pages 4 and 5, lines 147-150, and page 5, lines 159-160.

Reviewer 2 Report

This paper presents the design of polarizer reflectarray antennas. 

The authors need to provide a unit for lX1-lX2 and lY1-lY2 in Fig. 2.

The authors need to show the beam-scanning radiation performance.

The authors need to provide the Axial ratio versus Frequency for both LHCP and RHCP.    

 

Author Response

Please see the attachment

Author Response File: Author Response.pdf