Dealing with potential applications of metasurface in lens technologies, we propose a focusing metasurface with high polarized purity based on anisotropic elements, and then put it into application of high gain antenna with high polarized purity. Firstly, we design a metasurface cell with the polarization filtering characteristic, which is capable of transmitting the x-polarized waves efficiently while reflecting the y-polarized waves completely. By changing the metallic patch size, we can modulate the phase shift for the x-polarized transmitting waves. Then by imposing a hyperboloidal phase profile onto the surface, we design a metasurface lens with 105 mm × 105 mm in size, 21 × 21 in cell number, and 30 mm in focal length. According to the principle of reversibility of light path, the spherical waves emitted from the patch antenna can be converted into plane waves by the focusing metasurface lens, which is used to improve the antenna gain. As for the experiment, we tend to obtain the metasurface lens impinged by differently polarized waves in order to study the lens response to differently polarized waves. The results show that the metasurface acts as a lens when impinged by the x-polarized waves but serves as a reflector when illuminated by the y-polarized waves. That is to say, the y-polarized waves are mostly filtered out while the x-polarized waves are efficiently transmitted and focused, which is in good accordance with the designed principle. Assuming that a patch antenna emits the x/y-polarized waves at the focal point, we obtain not only the antenna gain improved remarkably but also polarized isolation above 25 dB in the operating bandwidth of the designed metasurface. The results of the antenna application give a further proof of the designed lens which eventually contributes to the high gain and high polarized purity of the lens antenna.%针对超表面在透镜方面的应用,基于各向异性超表面单元设计了一款高极化纯度的聚焦超表面透镜,并探讨了其在高增益高极化纯度天线方面的应用.设计了一款具有极化滤波特性的各向异性超表面单元,单元对x极化波保持高透性的同时,对y极化波保持近乎为零的透射率.利用该型单元设计了焦距为30 mm、阵列大小为105 mm×105 mm、单元数为21×21的聚焦超表面透镜.根据光路可逆原理,焦点处发出的球面波被超表面透镜有效转化为平面波,从而达到提高天线增益的目标.实验中分别用不同极化形式的球面波照射聚焦超表面来研究超表面对不同极化波的控制特性.结果表明,x极化波照射时,超表面工作于透镜模式,球面波转化为平面波,天线增益大大提高;y极化波照射时,超表面类似于金属板,将入射波全部反射;x/y极化混合波照射时,天线增益大大提高,且极化隔离度高于25 dB,充分说明设计的聚焦超表面在提高x极化波增益的同时可高效滤除y极化波,达到了高增益高极化纯度的目标.
展开▼
