A Wideband, Efficient Varactor-Tuned Reconfigurable Intelligent Surface Unit Cell for X-Band Beam-Steering Applications

Amani  Abduallah; Abdulkhalek  Zatout

doi:10.64516/k5q2q287

Authors

Amani Abduallah Omar Al-Mukhtar University, AL-Bayda, Libya Author
Abdulkhalek Zatout University of Derna, Derna, Libya Author

DOI:

https://doi.org/10.64516/k5q2q287

Keywords:

Reconfigurable Intelligent Surface (RIS), Unit Cell Design, X-band, Broadband Optimization, Varactor Diode, Beam Steering, Metasurfaces

Abstract

This paper presents the complete design, characterization, and system-level validation of a high-performance, varactor-tuned Reconfigurable Intelligent Surface (RIS) unit cell for the X-band. The proposed unit cell, adapted from a proven C-band topology, was optimized through a comprehensive parametric study to achieve robust broadband performance. The final design, which utilizes an F4B substrate with a geometric scaling factor of 0.40, demonstrates a wide operational bandwidth of 1.19 GHz (10.4% FBW) centered at 11.44 GHz. Across this band, it maintains a guaranteed maximum in-band insertion loss of 2.98 dB and an average phase agility of over 319°. At its operational center frequency, the unit cell achieves a continuous 321.9° phase swing with a worst-case insertion loss of only 1.99 dB, indicating minimal amplitude distortion. To validate its practical utility, a theoretical 20x20 RIS array was modeled. The results confirm precise quantized beam steering with a maximum pointing error of ≤ 0.3° and a low quantization gain loss of 0.88–1.11 dB for scans up to 45°. These validated, high-performance characteristics establish the proposed unit cell as a strong candidate for practical, next-generation X-band RIS applications.

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Author Biographies

Amani Abduallah, Omar Al-Mukhtar University, AL-Bayda, Libya

Electrical Engineering Department, Faculty of Engineering, Omar Al-Mukhtar University, AL-Bayda, Libya
Abdulkhalek Zatout, University of Derna, Derna, Libya

Electrical Engineering Department, Faculty of Engineering, University of Derna, Derna, Libya

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