Reconfigurable and Low-loss Millimeter-Wave Antennas using MEMS Paraffin Micro-actuators

可重构性是未来用于传感、成像、无线和卫星通信的敏捷毫米波（30-300 GHz）系统的基本特征。天线和射频（RF）电路是这种系统的组成部分，因为它们可以提供极化、带宽、波束转向、增益、辐射图案或特性阻抗控制等方面的变化。在过去，实现重新配置的关键器件是RF MEMS开关。然而，这些器件具有高致动电压、缺乏集成灵活性、可靠性和高成本的缺点。在这个提议中，我们引入了一类新的新材料和设备，以实现重新配置，而没有这些缺点。具体而言，我们认为石蜡相变材料（PPCMs）作为一个有前途的候选人。由于我们提出的PPCM器件的自然可重构性和低损耗架构，我们希望它们在传感，成像和无线/卫星通信系统中具有广泛的实用性。教育影响包括实践经验，通过夏令营和各种推广活动来培训学生进行材料表征，多物理场有限元模拟，设备制造和RF测试，以吸引工程专业的本科生和代表性不足的学生。对社会（社区）的影响包括：（1）可靠的高带宽手持设备和通信系统，用于大数据速率传输，以及（2）一类新的可靠的可切换设备，依赖于低成本，低电压/功率和低温制造，易于集成在未来的无线和通信设备中。这与其他相变材料的电相变（介电常数和电导率）形成对比。我们提出了可重构毫米波天线和RF电路，采用石蜡薄膜开发一类新的石蜡基相变材料，具有两个互补的功能：（1）低损耗操作，和（2）高度本地化的热机械微致动。PPCM应该允许在单个芯片上开发低损耗毫米波和RF电路和天线的长期目标。在过去，已经使用低温共烧陶瓷，但需要在极高的温度下烧结，使得它们与半导体加工不兼容。此外，它们不可重新配置。相比之下，已知石蜡在相对低的温度下经历15%的体积变化。此外，PPCM表现出低至0.0002的介电损耗。作为这项工作的一部分，第一次，我们建议证明石蜡基PCM的无源和可重构毫米波天线和RF调谐电路的可行性。所提出的PPCM具有以下关键特征：（1）极低的介电损耗，（2）利用相变特性在大带宽上用作热机械致动器，（3）可以单片集成在同一衬底上以实现连续重构。这些PPCM器件不仅避免了传统器件的可靠性问题，而且还提供了非常低的损耗和连续的重新配置。作为这项研究的一部分，我们将研究PPCM的材料和电气特性，开发设备，并检查它们集成到毫米波天线阵列和阻抗匹配电路。

Reconfigurability is an essential feature in future agile millimeter wave (30-300 GHz) systems used in sensing, imaging, wireless, and satellite communications. Antennas and radio frequency (RF) circuits are an integral part of such systems as they can provide changes in polarization, bandwidth, beam steering, gain, radiation pattern or characteristic impedance control, among others. In the past, key devices for achieving reconfiguration have been RF MEMS switches. However, these devices suffer from high actuation voltage, lack of integration flexibility, reliability, and high cost. In this proposal we introduce a new class of novel materials and devices to achieve reconfiguration without those shortcomings. Specifically, we consider paraffin phase-change materials (PPCMs) as a promising candidate. Owed to the natural reconfigurability and low-loss architecture of our proposed PPCM devices, we expect them to have wide utility in sensing, imaging, and wireless/satellite communication systems. Educational impacts include hands-on experiences to train students in material characterization, multi-physics finite element simulation, device fabrication, and RF testing through summer camps and a variety of outreach activities to attract undergrads and underrepresented students in engineering. Impact on society (community) include: (1) reliable high bandwidth handhelds and communication systems for large data rate transfers, and (2) a new class of reliable switchable devices that rely on low-cost, low voltage/power and low temperature manufacturing for ease of integration in future wireless and communication devices.Paraffin is a novel low loss dielectric that undergoes reversible volumetric mechanical phase change. This is in contrast to electrical phase change (permittivity and conductivity) of other phase-change materials. We propose reconfigurable millimeter wave antennas and RF circuits that employ paraffin film to develop a new class of paraffin-based phase change materials having two complimentary functions: (1) low-loss operation, and (2) highly localized thermo-mechanical micro actuation. PPCMs should allow the long standing goal of developing low-loss millimeter wave and RF circuits and antennas on a single chip. In the past, low temperature co-fired ceramics have been used but require sintering at extremely high temperatures, making them incompatible with semiconductor processing. Furthermore, they are not reconfigurable. By contrast, paraffin is known to undergo a 15% volumetric change at relatively low temperatures. Also, PPCMs exhibit a dielectric loss as low as 0.0002. As part of this effort, for the first time, we propose to demonstrate the feasibility of paraffin-based PCMs for passive and reconfigurable millimeter wave antennas and RF tuning circuits. The proposed PPCMs have the following key features: (1) extremely low dielectric loss, (2) exploit phase-change properties to function as thermo-mechanical actuators across a large bandwidth , (3) can be integrated monolithically on the same substrate to enable continuous reconfiguration. These PPCM devices not only avoid reliability issues of conventional devices, but also provide for very low-loss and continuous reconfiguration. As part of this research, we will study the material and electrical properties of PPCM, develop devices and examine their integration into millimeter wave antenna arrays and impedance matching circuits.