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摘要:
传统微波天线的空间分辨率受限于衍射极限，难以突破波长量级的约束，限制了其在高分辨率微波传感与检测中的应用。为克服这一问题，本文设计了一种全介质超衍射极限聚焦天线。首先，基于广义斯涅尔定律，利用非对称散射超构光栅阵列对天线表面功能化，通过调控电磁波前实现亚波长尺度高效光束聚焦。然后，对超构光栅的几何结构设计进行优化，实现高调控效率。最后，分析超构天线所生成焦斑的电场强度分布以及尺寸。仿真结果表明：超构天线调控效率达到98.50%，衍射效率为72.56%，且焦斑最小尺寸小于0.73
λ ，焦深约为15.11λ 。本文设计的超构天线兼具长焦深与高效率特性，其亚波长聚焦特性显著提升了空间分辨率，为微波成像及无损检测等领域的高精度传感检测提供了新的解决方案，具有潜在的应用价值。Abstract:Conventional microwave antennas are constrained by the diffraction limit, making it challenging to breakthrough the constraint of wavelength-scale, which hinders their application in high-resolution microwave sensing and detection. To overcome this limitation, this study designs an all-dielectric integrated meta-antenna with super diffraction-limited performance. First, the antenna surface is functionalized using an asymmetric scattering meta-grating array based on the generalized Snell's law, enabling efficient subwavelength beam focusing through precise electromagnetic wavefront manipulation. Then, the geometrical structural of the metagrating is optimized to achieve high-efficiency wavefront control. Finally, the electric field intensity distribution and size of the generated focal spot are analyzed. The simulation results demonstrate that the highest manipulation and diffraction efficiencies reach 98.50% and 72.56%. The achieved focal spot exhibits a subwavelength dimension below 0.73
λ with a focal depth of approximately 15.11λ . The designed meta-antenna simultaneously achieves long focal depth and high-efficiency, with its subwavelength focusing capability remarkably enhancing spatial resolution. It provides a novel solution for high-precision sensing and detection in fields such as microwave imaging, non-destructive testing, and biomedical diagnosis, demonstrating substantial potential for practical applications.-
Key words:
- metasurface /
- antenna /
- diffraction limit /
- long depth of focus
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图 1 超构光栅的原理和特性。(a) 基于非对称单元结构的超构光栅阵列结构示意图；(b) 不同衍射周期T−1阶的偏折角度；(c-e) 微波入射超构光栅阵列时，偏折角度分别为32.01°、22.05°和12.13°的模拟电场分布；(f) 不同衍射阶的透射光谱：T0、T−1、T+1、Ttotal分别表示衍射阶0、−1、+1和total的透射率。
Figure 1. Principle and characteristics of the metagrating. (a) Schematic diagram of the metagrating array structure based on asymmetric unit cells; (b) The deflection angles of T−1 order with different diffraction periods; (c−e) Simulated electric field distributions for microwave incidence on a metagrating array at deflection angles of 32.01°, 22.05°, and 12.13°; (f) Transmission spectra of different diffraction orders. T0, T−1, T+1, and Ttotal denote the transmission of diffraction order 0, −1, +1 and total, respectively
图 2 (a) 超构透镜设计原理图；(b) 基于超构光栅的超构透镜结构示意图
Figure 2. (a) Design schematic of metalens; (b) Schematic diagram of the metalens based on metagrating
图 3 (a-c) 不同衍射周期下T−1阶调控效率；(d) 超构光栅高度容差分析；
Figure 3. (a-c) The calculated manipulation efficiencies in T−1 order for different diffraction periods; (d) Analysis of height tolerance in metagratings.
图 4 (a) 超构透镜的电场强度分布；(b) 沿z轴方向的归一化强度分布图；(c) 在焦平面上沿x轴方向的归一化强度分布图
Figure 4. (a) Electric field distributions of the metalens; (b) Normalized intensity distribution along the z-axis direction, the inset marks the measurement position; (c) Normalized intensity distribution in the focal plane along the x-axis direction, the inset marks the measurement position in focal plane.
图 5 (a) 全介质超构天线示意图；(b) 全介质超构天线剖面图，包括波导接口、波束扩展组、喇叭天线和超构透镜
Figure 5. (a) Schematic diagram of all-dielectric meta-antenna; (b) Profile of all-dielectric meta-antenna, which including waveguide interface, beam expansion group, horn antenna, and metalens
图 6 (a) 超构天线聚焦电场强度分布；(b) 沿z轴方向的归一化强度分布图
Figure 6. (a) Focus electric field distributions of the meta-antenna; (b) Normalized intensity distributions along the z-axis direction
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