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.
