Anisotropic Microwave/Terahertz Metamaterials for Satellite Applications (ANISAT)

人们对联合王国空间部门在通信、成像和地球观测方面的兴趣越来越大。关键是发送和接收电磁波。为了实现更高的通信速率并获得更高的成像精度，通常使用更高的频率。该项目将利用微加工技术开发新结构，为卫星和地球段开发频率从28 GHz到1 THz的新型天线和偏振器。ANISAT将解决以下五个技术挑战：1）设计各向异性超材料;2）利用这些特性设计新型天线、偏振器和射频器件;3）开发测量这些特性的新方法;4）微制造异质各向异性结构; 5）将这些元素组合成一系列演示。下面将更详细地介绍上述五点：i）当电磁波穿过材料时，它会因介电特性而变慢。如果人造电介质可以由小的（与波长相比）矩形或椭圆形夹杂物组成，那么当入射电磁波具有不同的偏振时，这种复合材料将表现出不同的行为。这可以被用来创建圆极化天线，其中电场在时间上跟踪一个圆。这是空间通信的有利特性。ii）目前，介电测量仅考虑一种极化的介电特性，并有效地假设材料是各向同性的。ANISAT将开发一种新的测量系统，使用谐振超表面，可以测量所有三个轴的沿着属性。这将为天线和射频工程师打开一个新的自由度。iii）这些各向异性的人工晶体将用于设计新型的圆极化天线。由于馈电结构的小尺度，目前对馈电天线进行馈电以在50 GHz以上的频率处产生圆极化是具有挑战性的。高增益多波束腔天线和偏振器将在高达1 THz的频率范围内设计。iv）将使用3D打印来制造初始各向异性人工骨。这提供了简单且易于开发的制造工艺。然而，由于复合材料内部的小尺度空气/金属夹杂物的尺寸，上限频率范围被限制在约40 GHz。在这个频率以上，夹杂物接近波长的尺度，并且它们变得共振。为了扩展频率范围，将开发和利用洁净室中的新型微加工工艺。这些包括完全金属化的SU 8光致抗蚀剂聚合物和/或硅层，具有几微米尺度的高尺寸精度。五）学习过程将是多学科和迭代的，因为每个阶段都在创新。这两所大学地理位置接近，在这方面将非常有利。该计划是创建可以向工业展示的实验室演示器。这些临时措施包括：一种新型的介电测量系统;一种Ka波段（26 - 40 GHz）的高增益圆极化天线;一种频率高达110 GHz的圆极化法布里-珀罗天线;以及220 - 300 GHz和中心频率为640 GHz的线圆极化器和分束器。

There is growing interest in the UK space sector for communications, imaging and earth observation. Key to this is sending and receiving electromagnetic waves. To enable higher communication rates and get greater accuracy in imaging often higher frequencies are used. This project will develop new structures using microfabrication techniques to develop novel antennas and polarizers for satellites and the earth segment over frequencies from 28 GHz up to 1 THz. This frequency range overlaps and extends the currently used frequencies.ANISAT will address these five technical challenges:1) Designing anisotropic metamaterials;2) Exploiting these properties to design novel antennas, polarizers and RF devices;3) Developing novel methods of measuring these properties;4) Microfabricating heterogeneous anisotropic structures;5) Combining these elements into a series of demonstrators.The above five points are addressed in more detail below:i) When an electromagnetic wave moves through a material it is slowed down by the dielectric properties. If an artificial dielectric can be composed of small (compared to a wavelength) rectangular or elliptical inclusions, then this composite material will behave differently when the incident electromagnetic wave has different polarizations. This can be exploited to create circularly polarized antennas where the electric field traces a circle in time. This is an advantageous property for space communications. ii) Currently, dielectric measurements only consider the dielectric properties for one polarization and effectively assume the materials are isotropic. ANISAT will develop a novel measurement system using resonant metasurfaces that can measure the properties along all three axes. This will open a new degree of freedom for antenna and radiofrequency engineers. iii) These anisotropic artificial dielectrics will be used to design novel circularly polarized antennas. It is currently challenging to feed antennas to create circular polarization at frequencies above 50 GHz due to the small scale of the feed structure. High gain multi beam cavity antennas and polarizers will be designed at a range of frequencies up to 1 THz. iv) Initial anisotropic artificial dielectrics will be fabricated using 3D-printing. This provides a simple and readily exploitable fabrication process. However, the upper frequency range is limited to approximately 40 GHz by the size of the small-scale air/metal inclusions inside the composite. Above this frequency the inclusions approach the scale of a wavelength and they become resonant. To extend the frequency range, novel microfabrication processes in clean rooms will be developed and exploited. These include fully metallised SU8 photoresist polymers and/or silicon layers with a high dimensional accuracy of the scale of a few microns. v) The learning process will be multidisciplinary and iterative as each stage innovates further advances. The close geographical proximity of the two universities will be highly beneficial in this regard. The plan is to create laboratory demonstrators that can be showcased to industry. These provisionally include: a novel dielectric measurement system; a high gain circularly polarized antenna at Ka band (26 - 40 GHz); a circularly polarized Fabry-Perot antennas at frequencies up to 110 GHz; and linear to circular polarizers and beam splitters from 220 - 300 GHz and at a central frequency of 640 GHz.