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）电路是这种系统的一个组成部分，因为它们可以提供极化、带宽、波束转向、增益、辐射方向图或特性阻抗控制等方面的变化。在过去，实现重配置的关键器件是射频MEMS开关。然而，这些器件存在驱动电压高、集成灵活性差、可靠性差、成本高等问题。在这个建议中，我们引入了一类新的材料和器件来实现重构，而没有这些缺点。具体来说，我们认为石蜡相变材料（PPCMs）是一个有前途的候选材料。由于我们提出的PPCM器件具有自然的可重构性和低损耗架构，我们期望它们在传感、成像和无线/卫星通信系统中具有广泛的应用。教育影响包括通过夏令营和各种推广活动来培养学生在材料表征、多物理场有限元模拟、器件制造和射频测试方面的实践经验，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用于大数据速率传输的通信系统，以及(2)依赖于低成本，低电压/功率和低温制造的新型可靠可切换设备，以便于在未来的无线和通信设备中集成。石蜡是一种具有可逆体积力学相变的新型低损耗介质。这与其他相变材料的电相变（介电常数和电导率）形成对比。我们提出了可重构的毫米波天线和射频电路，利用石蜡膜来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，(2)高度局部化的热机械微驱动。ppcm应该允许在单个芯片上开发低损耗毫米波和射频电路和天线的长期目标。在过去，已经使用了低温共烧陶瓷，但需要在极高的温度下烧结，这使得它们与半导体加工不相容。此外，它们不能重新配置。相比之下，已知石蜡在相对较低的温度下会经历15%的体积变化。此外，ppcm的介电损耗低至0.0002。作为这项工作的一部分，我们首次提出证明石蜡基pcm用于无源和可重构毫米波天线和射频调谐电路的可行性。所提出的ppcm具有以下关键特征：(1)极低的介电损耗；(2)利用相变特性作为大带宽的热机械致动器；(3)可以单片集成在同一衬底上，以实现连续的重新配置。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。作为本研究的一部分，我们将研究PPCM的材料和电学特性，开发器件并检查其集成到毫米波天线阵列和阻抗匹配电路中。

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.