# Compact Beam-Scanning Reflectarray Antenna with SLL Reduction Using In-Plane Panel Translations
## 5 Conclusions  
A 1D beam-scanning RA antenna is presented as a cost-effective solution for millimeter-wave satellite communication terminals. The antenna is designed to prioritize mechanical simplicity while featuring a remarkably low focal ratio of \(F/D_{y}=0.47\). Despite using a simple steering approach based on in-plane panel movements, a continuous scanning range of 45 degrees is covered with a low scan loss of only 1.1 dB and a gain of 31.6 dBi. Compared to existing works, this antenna achieves a higher gain and comparable or lower scanning losses while featuring a significantly more compact form factor. To design this antenna, a multi-stage process is used. First, the scanning range is gradually expanded, while ensuring a highly uniform beam level across the entire scanning range. Once the desired range is achieved, a novel technique is proposed to reduce the SLLs without degrading the antenna's performance. To do so, a multi-focal optimization is re-purposed to negatively bias collimation in the direction of the side-lobe, achieving a SLL reduction of up to 2.3 dB. To the best of the authors' knowledge, this is the first application of a multi-focal optimization in such a way. Its use was motivated by the particular challenges created by such a low focal ratio, but this technique should be applicable to other future mechanically scanned reflectarray antenna designs.  
Conceptualization, A.G.-A., S.A.M. and C.A.F.; investigation, A.G.-A., S.A.M., M.A., M.R.P. and C.A.F.; design process implementation, A.G.-A.; validation (simulation). S.A.M. and C.A.F.; validation (measurements), A.G.-A., M.A. and M.R.P.; writing--original draft preparation, A.G.-A.; writing--review and editing, A.G.-A., S.A.M., M.R.P. and C.A.F.; supervision, M.A. and M.R.P. All authors have read and agreed to the published version of the manuscript.  
This work was supported in part by MCIN/AEI/10.13039/501100011033 under grants PID2020-114172 RB-C21, PID2023-146246 OB-C32, and TED2021-130650B-C22, co-funded by the EU (European Union) \"NextGenerationEU\"/PRTR; by Ministerio de Educacion y Formacion Profesional, under grant FPU20/07267; and by FCT/MECI through national funds and, when applicable, co-funded EU funds under UID/50008: Instituto de Telecomunicacoes.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors upon request.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Ref.** & **Approach** & **CS/MB (1)** & **Freq.** & **Max.** & **Scan** & **Scan** & **Agent.** & **F/D** & **Band-Width** & **SLL (dB)** \\ \hline
[19] & Folded RA with polarizer, feeders embedded in panel & MB & 26.5 & 24.6 & 58 & 2.1 & 15.0\% & 0.71 & \(\frac{12.6\%}{3\text{ }}\) & \(-8.5\) \\ \hline
[22] & Folded RA, Risley prism using two rotating panels & CS & 10.0 & 21.5 & \(\theta\leq 45\) (2D) & 2.3 & 31.2\% & 0.84 & \(\frac{11.5\%}{3\text{ }}\) & NA (1) \\ \hline
[17] & Multiple feeds along tilted focal arc & MB & 29.5 & 28.2 & 90 & 0.5 & 6.8\% & 0.58 & \(\frac{6.8\%}{1\text{ }}\) & NA (1) \\ \hline
[23] & Feed movements along focal arc and panel rotations & CS & 12.0 & 26.2 & 140 & 4.9 & 42.5\% & 1.0 & \(\frac{4.2\%}{1\text{ }}\) & NA (1) \\ \hline
[27] & Linear panel translations using rollable panel & CS & 14.0 & 25.1 & 42 & 1.5 & 17.9\% & 0.8 & NA (1) & \(-15.0\) \\ \hline This work & In-plane linear panel translations & CS & 29.5 & 31.6 & 45 & 1.1 & 24.7\% & 0.47 & \(\frac{11.9\%}{1\text{ }}\) & \(-9.9\) \\ \hline \hline \end{tabular} \({}^{(1)}\) CS: Continuous Scanning; MB: Multi-beam; NA: Not Available. \({}^{(2)}\) Efficiency is calculated for all entries using the definition stated in this paper. Other equally valid criteria may be used in the listed works.  
\end{table}
Table 2: Comparison with other related beam scanning designs.