Investigation of Novel Microwave Components Enabled by Additive Manufacturing

Abstract

This dissertation investigates the application of additive manufacturing to novel microwave components, including a dielectric-loaded antenna, an antenna solution for intra-chip wireless interconnects, an all-dielectric wave-bending structure for Ka-band and a compact multiband antenna for mobile device applications. First, a novel methodology is proposed to control antenna radiation pattern based on 3D printing of specially-designed dielectric material, which realizes spatially-dependent dielectric constants around the antenna. As a proof of concept, we design a quarter-wavelength monopole antenna surrounded by a 3D-printed polymer structure with an optimized dielectric property distribution. Unlike the conventional donut-shaped pattern of a quarter-wavelength monopole antenna, one-beam and multiple-beam patterns are obtained using a genetic-algorithm-based optimization. Different dielectric constant spatial distributions are realized by changing the ratio of the dielectric to air at the unit cell level in the entire antenna volume. A two-beam monopole prototype is designed, fabricated and tested. Second, we introduce a novel antenna design enabled by 3D printing technology for future wireless intra-chip interconnects with applications to multicore architectures and system-on-chips (SoCs). In the proposed design, vertical quarter-wavelength monopoles at 160 GHz on a ground plane are used to avoid low antenna radiation efficiency caused by the silicon substrate. The monopoles are surrounded by a specially-designed dielectric distribution. This additional degree of freedom in design enabled by 3D printing technology is used to tailor wave propagation path. Simulation results show that the proposed dielectric loading approach improves the desired link gain by 8-15 dB and reduces the undesired link gain by 9-23 dB from 155 to 165 GHz. As a proof-of-concept, a 60 GHz prototype is designed, fabricated and characterized. The measurements match the simulation results and demonstrate 10 - 18 dB improvement of the desired link gain and 10 - 30 dB reduction in the crosstalk from 55 to 61 GHz. The demonstrated path loss of the desired link at a distance of 17 mm is only 15 dB, which is over 10 dB better than the previously reported work. Moreover, based on liquid crystal material, we can achieve reconfigurable antennas for intra-chip wireless interconnects. Third, a 90° wave-bending structure at Ka-band (26.5 - 40 GHz) based on 3D-printed metamaterial is designed, fabricated and measured. The wave-bending effect is realized through a spatial distribution of varied effective dielectric constants. Based on the effective medium theory, different effective dielectric constants are accomplished by special, 3D-printable unit cells, which allow different ratios of dielectric to air at the unit cell level. In contrast to traditional, metallic-structure-included metamaterial designs, the reported wave-bending structure here is all dielectric and implemented by the polymer-jetting technique, which features rapid, low-cost and convenient prototyping. Lastly, a compact multi-band antenna compatible with a metallic packaging for mobile devices is proposed. The antenna covers band-1 698 - 787 MHz and band-2 1710 - 2155 MHz, enabling LTE 2 / LTE 4 / LTE 12 / LTE 13 / GSM1900 applications. The current distribution shows that the quarter-wavelength, half-wavelength and one-wavelength modes together contribute to the radiation in both bands. A four-element LC circuit is utilized for antenna bandwidth matching. The antenna is fabricated and measured. Close agreement between the measurement results and simulation results is observed.