Micromachined Circuits For Terahertz Communications

EPSRC有一个交付计划，使其投资组合与英国的优势和国家重要性领域保持一致，并指定了一些“增长”领域。该应用程序解决了其中的两个领域：“RF和微波通信”和“RF和微波设备”，特别匹配后者的太赫兹技术方面。为什么EPSRC强调这些领域？答案是，随着对数字信息交换的需求不断增加，社会正在不断发展。人们期望每个人都能永久连接到互联网，无论他们身在何处。人们期望立即提供更多更高质量的信息：因此，更新的服务需要越来越高的数据量和传输速率。点播视频就是一个很好的例子，现在标准清晰度的家庭交付已经很常见，新的4k点播视频正在进行演示。这些服务所需的数据传输速率是巨大的，基础设施需要适应，实现这一目标的一种方法是移动到更高的无线链路频率。我们建议为这样的通信系统展示新的构建块组件，在全新的基础上设计和构建这些组件。选择300 GHz的频率是因为它处于技术的尖端;系统现在被部署在低于约100 GHz的频率，而接近1000 GHz的系统由于缺乏有源电路而需要几年时间。这些组件也将适用于雷达和传感场景。一旦示范了各个组成部分，将设计、建造和测试一个完整的通信系统。300 GHz通信系统的演示非常少，独特的设计方法将提供世界级的演示。三个小组正在合作进行这个项目：弗赖堡的弗劳恩霍夫研究所，德国（IAF），英国卢瑟福阿普尔顿实验室（RAL）和伯明翰大学。所有的合作伙伴都具有在这些非常高的频率下的设计和测量能力。IAF是亚毫米波集成电路生产的世界领先者，将为放大器提供晶体管。RAL将提供世界一流的肖特基势垒，伯明翰大学拥有先进的微加工能力。伯明翰开发了一种新的互连原理来连接肖特基二极管和晶体管。代替使用导线及其类似物，将使用基于中空波导管的谐振腔。目前，300 GHz组件安装在传统的铣削镀金块。所需的波导尺寸约为0.8 mm × 0.4 mm。虽然传统的铣床可以加工，但一旦需要谐振器的内部结构，铣削就变得困难或不可能。一种可用于波导腔和更高频率下的更小谐振器的技术是微机械加工。伯明翰大学已经展示了300 GHz及以上的微加工波导、滤波器、双工器和天线。这项技术现在已经为下一步做好了准备，即包括有源和非线性器件。伯明翰的微机械加工工作已经通过多种技术完成，主要技术是通过蚀刻称为SU8的紫外线敏感光刻胶。这允许通过掩模以光刻方式定义图案，然后蚀刻部分产生波导。最终的结构是通过将许多SU8蚀刻层结合在一起，然后对其进行金属涂覆而制成的。SU8波导的性能已被证明与金属一样好。微加工电路的其他技术将进行调查，以找到最佳的解决方案。

EPSRC have a delivery plan to align their portfolio to areas of UK strengths and national importance and have designated a number of 'Grow' areas. This application addresses two of these areas: 'RF and microwave communications' and 'RF and microwave devices', specifically matching the terahertz technology aspect of the latter.Why has EPSRC highlighted these areas? The answer is that society is evolving with a continuously increasing demand for the exchange of digital information. There is an expectation that everyone will be permanently connected to the Internet, no matter where they are. People are expecting that more information of a higher quality is delivered immediately: therefore newer services are requiring higher and higher data volumes and transfer rates. On demand video is an excellent example, with in-home delivery with standard definition now common place and demonstrations of new 4k on demand video now taking place. The data rates expected for these services are vast and the infrastructure needs adapt to cope.One way to achieve this is to move to higher frequencies for wireless links. We propose to demonstrate new building block components for such a communications system, designing and building these on an entirely new basis. A frequency of 300 GHz is chosen as it is at the cusp of technology; systems are now being deployed at frequencies below about 100 GHz where as systems approaching 1000 GHz are some years away because of the lack of active circuits. The components will also be applicable in radar and sensing scenarios. Once the individual components have been demonstrated, a full communications system will be designed, built and tested. There are very few demonstrations of communication systems at 300 GHz and the unique design methodology will provide a world-class demonstration.Three groups are collaborating in this project: the Fraunhofer Institute in Freiburg, Germany (IAF), and it the UK the Rutherford Appleton Laboratory (RAL) and Birmingham University. All partners have substantial design and measurement capabilities at these very high frequencies. IAF are world leaders in the production of submillimetre wave integrated circuits and will be supplying transistors for the amplifiers. RAL will deliver world class Schottky barrier and the University of Birmingham has advanced micromachining capabilities. At Birmingham a new interconnect principle has been developed to link the Schottky diodes and transistors. Instead of using wires and their analogues, hollow waveguide tube based resonant cavities will be used. Currently 300 GHz components are mounting in conventionally milled gold pated blocks. The required waveguide dimensions are about 0.8 mm by 0.4 mm. Although conventional milling machines can machine this, once internal structures for resonators are required, milling becomes difficult or impossible. A technology that can be used for the waveguide cavities, and for smaller resonators at higher frequencies, is micromachining. Birmingham University have demonstrated micromachined waveguides, filters, diplexers and antennas at and above 300 GHz. This technology is now ready for the next step, which is the inclusion of active and non-linear devices. The micromachining work at Birmingham has been done by a number of techniques, the primarily technique is by etching an ultraviolet sensitive photoresist called SU8. This allows a pattern to be defined photolithographically by a mask and then etching sections produces the waveguide. The final structure is made by bonding a number of SU8 etched layers together and then metal coating them. The performance of the SU8 waveguides has been shown to be as good as metal. Other techniques for micromachining circuits will be investigated in order to find the optimum solution.