This presentation was made at the 2019 NAFEMS World Congress in Quebec Canada
Metal Additive Manufacturing (AM) has matured as a technology and has assumed capabilities at the level of mass production. This has spurred interest in using the technology for microwave engineering applications including the fields of advanced driver assistance systems (ADAS) and 5G applications. Metal AM radio frequency components increasingly are becoming cost-competitive while providing added robustness when compared to similar components manufactured using electroplated thermoplastic or dielectric materials. Additionally, unique capabilities of AM allow for part consolidation and design optimization. This work illustrates the use of multi-physics simulation techniques for design and process optimization of these RF applications.
The antenna or antenna array require strict control of dimensional tolerances in order to achieve target radio frequency performance. The distortions inherent to AM process may affect the geometric tolerances resulting in unacceptable deviation from target performance. This is of a particular concern in metal additive manufacturing where the melting temperature is relatively high (600C-1700 C) creating large thermal gradients. Here a coupled transient thermal and structural simulation offers useful predictive capability. The layer by layer simulation is able to predict thermal and mechanical deformation history based on input AM process parameters such as deposition thickness, laser speed and scanning pattern for a powder bed fusion type manufacturing process. The resulting deformed geometry representing “as-built” geometry can be further validated for its electromagnetic and structural performance with respective simulations. If the RF or structural performance is not within acceptable range, a distortion-compensated geometry is created based on the results of the initial process simulation using a “inverse-problem” methodology. The distortion-compensated geometry becomes the new geometric input to the process simulation. Successive iterations of the process simulation with distortion compensation arrive at a geometry that when printed, achieves a component that is within specified tolerance of the as-designed geometry.
The demonstration applications include a K-band stepped, double-ridged square horn antenna and a slotted array printed in Copper and Aluminum Alloys. The simulation workflow for design and process optimization can be easily adapted to other RF components such as waveguides and phased array antennas with complex feeding networks.
Once the AM process is validated as a viable process for the existing design, it could be used to print novel designs that are outside the realms of traditional manufacturing techniques. Simulation is useful in determining optimum design for AM. The design optimization criteria considered here are based on specific operating conditions. For instance, antennae deployed on satellites are highly benefited from reduced weight. Redesigning the antenna array to consolidate assembly that can be printed as a single part offers one avenue of weight reduction. This approach has the additional benefit of reducing the electromagnetic insertion losses as the number of assembly component goes down. The second avenue to reduce weight comes from light-weighting the structural design for vibrational, structural and thermal loads. Structural, Electromagnetic and Topology Optimization based simulation techniques reduce the number of design iterations and optimize the structural robustness and electromagnetic performance at the same time.
|Date||18th June 2019|