This letter presents a broadband 3-D-printed circularly polarized (CP) spherical Luneburg lens (LL) with the linearly polarized feed antenna for the X-band. In order to implement spatially continuous varying effective refractive index (RI), the proposed LL is divided to many unit cells and their effective RI is simulated and calculated by effective medium theory. Since the effective RI of unit cells is anisotropic for two orthogonal linearly polarized (LP) waves, the proposed LL is an LP to CP polarizer realized by properly selecting the radius of the LL. The whole structure is fabricated by low cost 3-D-printing (3DP) technic, which is fed by an LP antenna source rotated to a certain angle with respect to the LL around the normal. The measured results indicate that the voltage standing wave ratio (VSWR), axial ratio, and gain enhancement are lower than 2, less than 2.8 dB, and more than 10 dB at X-band, respectively. The results of measurement agree well with the simulation.

中文翻译：

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X 波段宽带 3D 打印圆偏振球面 Luneburg 透镜天线的设计


这封信介绍了一种宽带 3D 打印圆偏振 (CP) 球面 Luneburg 透镜 (LL)，带有用于 X 波段的线偏振馈电天线。为了实现空间上连续变化的有效折射率（RI），所提出的LL被划分为许多晶胞，并通过有效介质理论模拟和计算它们的有效RI。由于晶胞的有效 RI 对于两个正交的线性偏振 (LP) 波是各向异性的，因此所提出的 LL 是通过正确选择 LL 的半径来实现的 LP 到 CP 偏振器。整个结构采用低成本3D打印（3DP）技术制造，由LP天线源馈电，该天线源相对于法线周围的LL旋转一定角度。测量结果表明，X波段电压驻波比(VSWR)、轴比和增益增强分别低于2、小于2.8 dB和大于10 dB。测量结果与模拟结果非常吻合。