Liquid Antennas

天线作为无线电系统和“物联网”必不可少的设备，在各种无线产品中都有很高的需求。传统上，它是由良好的导电材料（如铜）制成的，以尽量减少欧姆损失，最大限度地提高辐射效率。然而，导电/金属天线在某些应用中并不理想。例如，在较低的频率下，它们通常又大又重又昂贵。它们也会产生相对较大的雷达横截面，这不利于军事应用。此外，它们是固体的——一旦天线被制造出来，就很难使它们在电磁性能和机械结构方面重新配置和灵活。近年来，人们对水天线进行了研究，发现水天线可以克服传统金属天线面临的许多问题，并具有体积小、经济高效、透明、灵活、可重构等独特的特点。然而，它们不能在低温（例如低于0摄氏度）下工作，并且可能存在低辐射效率和低功率处理能力的问题，因此不适合实际应用。因此，在现实世界的广泛应用中，需要更好的水天线和传统金属天线的替代品。在这个项目中，我们将开发一种新型天线：液体天线，它具有水天线的所有优点，但克服了水天线的问题。主要挑战是1)如何确定最合适的液体材料，具有低损耗，热和机械稳定性，将在所需的温度范围（从-30到+60摄氏度），频率范围（从kHz到GHz）和射频/微波功率范围（高达kW）下工作。2)如何设计和制造紧凑、高效的液体天线，在主要天线参数（如工作频率、辐射方向图和尺寸）方面具有灵活性或可重构性，适合于实际应用。这是一个跨学科的项目，需要来自射频（RF）和微波工程、化学和材料科学的专业知识。它包括理论工作和实验工作。广泛的液体材料（不限于水和海水）将被研究，特别是离子液体和防冻液。它们的电磁、热学和机械性能将根据温度、频率和射频/微波功率水平进行筛选，最终目标是使可重构的小型液体天线在广泛的温度、频率和功率范围内高效工作。此外，还将深入研究适用于液体天线的可重构技术，并将开发两种可重构液体天线，并对其进行优化，以展示其在军事和商业应用方面的卓越潜力。这项工作将与工业领导者（BAE系统公司和华为）和学术专家（香港的陆教授）合作进行，以确保这项研究将为材料科学和无线电工程带来新的知识，一种新型天线将被引入以满足行业需求，并为无线世界提供另一种紧凑可重构和/或灵活的设备。本研究的研究成果（如液体和可重构技术）可以扩展到其他可能使用低损耗介质材料的射频和微波器件（如滤波器，延迟线和移相器）。

The antenna, as an essential device for radio systems and "Internet of Things", is in high demand in a wide range of wireless products. It has traditionally been made of good conductive materials (such as copper) to minimise the ohmic loss and maximise the radiation efficiency. However conductive/metal antennas are not ideal for some applications. For example, at lower frequencies, they are normally large, heavy and expensive. They also produce relatively large radar cross sections which are not good for military applications. Furthermore, they are solid - once the antennas are made, it is hard to make them reconfigurable and flexible in terms of the electromagnetic performance and mechanical configurations. Recently, water antennas have been studied and found that they could overcome many problems facing the traditional metal antennas and offer some attractive and unique features, such as small in size, cost effective, transparent, flexible and reconfigurable. However, they cannot work at low temperatures (e.g. below 0 degree C) and may suffer from low radiation efficiency and low power handling capacity problems, which make them not suitable for practical applications. Thus, better alternatives to water and conventional metal antennas are required for a wide range of real world applications.In this project, we are going to develop a new type of antenna: liquid antennas, which will offer all the advantages but overcome the problems that water antennas have. The main challenges are1) How to identify the most suitable liquid materials with low loss, thermal and mechanical stability which will work over the desired temperature range (from -30 to +60 degree C), frequency range (from kHz to GHz), and RF/microwave power range (up to kW).2) How to design and make compact and efficient liquid antennas which are flexible or reconfigurable in terms of the main antenna parameters (such as the operational frequency, radiation pattern, and size) and suitable for real world applications. This is an interdisciplinary project which requires expertise from radio frequency (RF) and microwave engineering, chemical and material science. It consists of both theoretical and experimental work. A wide range of liquid materials (not limited to water and sea water) will be studied, especially ionic liquids and antifreezes. Their electromagnetic, thermal and mechanical properties will be screened against temperature, frequency and RF/microwave power levels with the ultimate goal being to make reconfigurable, small liquid antennas to work efficiently and effectively over a wide temperature, frequency and power range. In addition, the reconfigurable techniques suitable for liquid antennas will also be studied thoroughly and two reconfigurable liquid antennas will be developed, optimised to demonstrate their excellent potential features for both military and commercial applications. The work will be undertaken in collaboration with industrial leaders (BAE Systems and Huawei) and academic expert (Prof Luk from Hong Kong) to ensure that this research will bring new knowledge into material science and radio engineering, a novel type of antenna will be introduced to meet the demands from the industry and provide an alternative compact reconfigurable and/or flexible device to the wireless world. The research outcomes of this study (e.g. the liquid and reconfigurable technology) could be extended to other RF and microwave devices (such as filters, delay lines and phase shifters) where low-loss dielectric materials may be used.