• 3-D printed heterogenous substrate bandpass filters

      Nesheiwat, Issa (2021-09)
      With the demand for increasing frequencies in today’s communications systems, compact integrated circuits are challenging to achieve. Compact filters have typically been realized by modifying the circuit design including using LC resonators, defective ground structures, and adjusting the length ratios of resonators. Heterogenous substrates with controlled regions of dielectric loading offer a new design approach when it comes to manufacturing an RF component. In this thesis, additive manufacturing is used to selectively place low-K and high-K dielectric materials to achieve a compact form factor, improved bandwidth, and higher suppression in re-entry modes. First, microstrip coupled strip lines are simulated to model the basic coupling effects of loading a substrate. Next, three 2.45GHz parallel coupled bandpass microstrip filters are designed with differing substrates: low-K, high-K and high-K loaded to analyze the impact of loading within the substrate. The filter substrates are manufactured using a dual-extrusion FDM 3-D printer to combine both dielectrics, low-K ABS, and high-K PrePerm ABS1000, into a single heterogeneous substrate. Compared to the low-K dielectric alternative, the high-K loaded filter demonstrated a 30.8% decrease in length, while maintaining similar bandwidth and suppression of re-entry modes. Compared to the high-K filter, the high-K loaded filter showed a 9.4dB reduction in re-entry mode suppression, while maintaining similar footprint size.