Micromachined Circuits For Terahertz Communications

EPSRC有一个交付计划，使他们的投资组合与英国的优势和国家的重要性保持一致，并指定了一些“增长”领域。该应用程序解决了其中两个领域：“射频和微波通信”和“射频和微波设备”，特别是与后者的太赫兹技术方面相匹配。为什么EPSRC强调这些领域？答案是，社会在不断发展，对数字信息交换的需求不断增加。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。人们希望更多、更高质量的信息能够即时传递，因此更新的服务对数据量和传输速率的要求越来越高。点播视频就是一个很好的例子，标准清晰度的家庭交付现在很常见，新的4k点播视频正在进行演示。这些服务的预期数据速率是巨大的，基础设施需要适应以应对。实现这一目标的一种方法是移动到更高频率的无线链路。我们建议为这样的通信系统展示新的构建模块组件，在全新的基础上设计和构建这些组件。选择300千兆赫的频率是因为它处于技术的尖端；系统现在部署在100 GHz以下的频率，而由于缺乏有源电路，接近1000 GHz的系统还需要几年的时间。这些组件也将适用于雷达和传感场景。一旦单个组件得到验证，将设计、建造和测试一个完整的通信系统。300 GHz通信系统的演示很少，而独特的设计方法将提供世界级的演示。三个小组正在合作这个项目：德国弗莱堡的弗劳恩霍夫研究所（IAF），英国的卢瑟福阿普尔顿实验室（RAL）和伯明翰大学。所有合作伙伴在这些非常高的频率上都有大量的设计和测量能力。IAF是生产亚毫米波集成电路的世界领先者，并将为放大器提供晶体管。RAL将提供世界一流的肖特基屏障，伯明翰大学拥有先进的微加工能力。在伯明翰，一种新的互连原理被开发出来，用于连接肖特基二极管和晶体管。代替电线和它们的类似物，将使用基于空心波导管的谐振腔。目前，300 GHz的组件都安装在传统的镀金块上。所需的波导尺寸约为0.8 mm × 0.4 mm。虽然传统铣床可以加工，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高频小谐振器的技术是微加工。伯明翰大学已经展示了300 GHz及以上的微机械波导、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设备。伯明翰的微机械加工工作已经通过许多技术完成，主要技术是通过蚀刻一种称为SU8的紫外线敏感光刻胶。这允许通过掩模光刻来定义图案，然后蚀刻部分产生波导。最终的结构是通过将一些SU8蚀刻层粘合在一起，然后涂上金属涂层制成的。SU8波导的性能已被证明与金属一样好。为了找到最佳的解决方案，我们将研究微加工电路的其他技术。

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.