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Loss-Optimized Reconfigurable Nonlocal Metasurface-aided Cavity Antenna

Minwoo Cho, Minseok Kim

Abstract

This paper presents the design and experimental demonstration of a reconfigurable cavity excited nonlocal metasurface antenna capable of wide angle dynamic beam steering. The antenna is synthesized using a volume surface integral equation based framework that rigorously captures nonlocal mutual coupling among metasurface unit cells. To ensure physical consistency, the numerically characterized resistance and reactance relationship of the tunable unit cells is directly incorporated into the synthesis, enabling precise far-field synthesis while minimizing Ohmic losses. The proposed approach is applied to a 10 GHz cavity fed metasurface antenna composed of 24 independently controlled varactor-loaded unit cells. Numerical simulations and near-field measurements demonstrate stable beam steering with a range of 80 degrees across broadside with excellent agreement between measured and simulated radiation patterns. These results confirm the effectiveness of the proposed framework for the realization of compact, reconfigurable cavity-excited metasurface antennas.

Loss-Optimized Reconfigurable Nonlocal Metasurface-aided Cavity Antenna

Abstract

This paper presents the design and experimental demonstration of a reconfigurable cavity excited nonlocal metasurface antenna capable of wide angle dynamic beam steering. The antenna is synthesized using a volume surface integral equation based framework that rigorously captures nonlocal mutual coupling among metasurface unit cells. To ensure physical consistency, the numerically characterized resistance and reactance relationship of the tunable unit cells is directly incorporated into the synthesis, enabling precise far-field synthesis while minimizing Ohmic losses. The proposed approach is applied to a 10 GHz cavity fed metasurface antenna composed of 24 independently controlled varactor-loaded unit cells. Numerical simulations and near-field measurements demonstrate stable beam steering with a range of 80 degrees across broadside with excellent agreement between measured and simulated radiation patterns. These results confirm the effectiveness of the proposed framework for the realization of compact, reconfigurable cavity-excited metasurface antennas.
Paper Structure (5 sections, 6 equations, 5 figures, 1 table)

This paper contains 5 sections, 6 equations, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Proposed Architecture and Unit-Cell Characterization
  3. VSIE-based Design Framework
  4. Numerical and Experimental Validation
  5. Conclusion

Figures (5)

  • Figure 1: (a) Three-dimensional view of the proposed tunable cavity-excited metasurface antenna operates at 10 GHz ($\lambda_0\approx30$ mm), comprising 24 varactor-loaded unit cells with individually connected bias lines for independent voltage control. (b) Simplified numerical model, where the physical unit cell is represented by an impedance strip with a surface impedance of $\eta_n$. All dimensions are specified in millimeters (mm).
  • Figure 2: (a) Periodic boundary setup for matching a physical varactor-loaded unit cell to a homogenized complex impedance strip $\eta_n$. (b) Mapping of $\eta_n$ as a function of $\mathbf{V}_\mathrm{b}$ via second-order polynomial interpolation.
  • Figure 3: (a) Comparison between HFSS simulation results (solid lines) and near-field measurement results (dashed lines). (b) Measured input reflection coefficients for all steering angles, satisfying $|S_{11}| < -10$ dB.
  • Figure 4: Fabrication and assembly sequence of the cavity-excited metasurface antenna, including CNC machining of the aluminum cavity, PCB fabrication of the varactor-loaded metasurface, and step-by-step assembly into the prototype.
  • Figure 5: Near-field measurement setup.