ABSTRACT

Wireless communications and interconnected devices have become ubiquitous in our everyday life. As the rollout of the 5th generation (5G), wireless communication technology is well underway, the number of interconnected devices is increasing exponentially. Estimations for 2021 predicted that 1.5 billion smart devices would sell globally, representing a $53.45 billion market size by 2022. With the increase of communication channels and transmitted data within these networks, the  challenge of coexistence without interference will become prominent. Simultaneously, 5G networks are introducing more frequency bands while densifying the network of communication towers. Forecasts predict a 100X increase of the network at the edge by introducing small cell towers, with projections estimating 45 million installed by 2031. As a result, rapid exponential growth in hardware costs is expected. Also, these dense networks will require a higher degree of self-configuration to prevent adjacent bands interference.

Tunable filters and large-scale manufacturing technologies are two solutions to address these challenges. Reconfigurable high-quality evanescent-mode (EVA) filters have been extensively presented in the literature. Different mechanisms have been employed for tuning, such as piezoelectric actuators and motors, and magnetostatic and electrostatic actuators. Furthermore, these implementations have been realized with printed circuit board (PCB) technology, computer numerical control (CNC) machining, 3D printing, and silicon (Si) micro-machining. Specifically, PCB manufacturing of three-dimensional front-end tunable filters has been quite promising and can deliver excellent performance. In addition, they can be integrated into the existing manufacturing lines and circuitry for the RF front-end. Nonetheless, there are limitations in fabrication tolerances that PCB manufacturing could reach. Consequently, there are restrictions on the frequency bands in that these devices can be manufactured as dimensions become smaller in higher bands. Also, cost limitations per unit built are significant compared to other technologies like injection molding. The research goal of this work is to investigate scalable, low-cost manufacturing processes and techniques while maintaining a high-performance device. Explicitly, combining knowledge from silicon RF MEMS tuned EVA filters and the cost-effective mass manufacturing injection molding technology to deliver a high-Q, high power handling, and low-cost tunable filter.