A Switched-Line Phase Shifter Fabricated with Additive Manufacturing

Abstract

Additive manufacturing, also known as 3D printing, has proven to be advantageous compared to conventional planar methods when utilizing the volume of a structure to miniaturize the design. The use of additive manufacturing can allow for high frequency circuitry to be conformed to an arbitrary shape while maintaining or enhancing performance. Recent advancements in low loss materials applicable to additive manufacturing have pushed performance levels even further. Utilizing additive manufacturing to build a three dimensional structure can improve factors such as reliability and repeatability by making the structure one solid piece as opposed to assembling multiple planar objects into the 3D shape. This allows the circuitry to be built around the structure. With this design approach other considerations, such as stability and strength, can be concentrated on during the structure design to realize new shapes. The purpose of this work is to investigate a 3D printed material, ULTEM, for radio frequency use and design a switched line phase shifter using the derived material properties. The first step in any high frequency circuit design is to have accurate material properties. An efficient way to determine the permittivity and loss tangent of a material is to place a ring resonator on the substrate and measure the resonant frequency and Q factor. An equivalent circuit model can then be built to match the measured response and the material properties extracted through circuit theory. From here accurate transmission line models can be analyzed to optimize the performance of the RF circuit. In this paper a ring resonator was designed on ULTEM to characterize the material properties. A 90° phase shifter was then fabricated on a 3D printed ULTEM substrate and a benchmark model was fabricated using traditional planar methods on Rogers RO4003C substrate. A comparison between the two models is given in this paper.