THE IDEA: INCREASE AUTOMATION IN THE DESIGN PROCESS
Apollo Microwaves is a leading supplier of microwave communication components and sub-systems for the satellite and wireless communication industries. They design and manufacture both standard and custom-engineered components for frequencies ranging from 1 GHz to 60 GHz, which means that their product range needs to be very wide.
Over the course of developing such a broad range of components, many of the same design tasks arise again and again. Complex components can be built up from many basic elements, such as the power combiner and coupler shown in Figure 1, and each component needs to be designed and optimized individually before the entire subsystem can be constructed. Creating these individually was a relatively straightforward process, but one that took a considerable amount of time from the engineers and prevented them from working on the more interesting design tasks. As a result, Apollo sought to automate their component design process by introducing electromagnetic simulation with CST Studio Suite®....
Figure 1 WR 28 4-way power combiner (top) and WR 112 triple cross-guide coupler (bottom).
THE CHALLENGE: DESIGNING AND OPTIMIZING VERY SENSITIVE COMPONENTS EFFICIENTLY
For many components, analytical models exist as a starting point for the design. However, the simplifications involved in these models mean that they need fine-tuning for high performance applications. To reduce the amount of work involved in the fine-tuning process, Apollo took advantage of the link between Microsoft Excel®, which they use to calculate the initial parameters for designing components like couplers, and CST Studio Suite, which they use to simulate and adapt the design as necessary.
With the VBA scripting language common to both software tools, they were able to create a macro that constructs a 3D model of the component in CST Studio Suite using the parameters from Excel (Figure 2). This parameterized model is then optimized using the frequency-domain solver and the built-in optimization tools in CST Studio Suite in order to automatically tune the model and improve its performance.
Figure 2 CST Studio Suite models of the WR28 4-way power combiner (top) and the WR 112 triple cross-guide coupler (bottom). For both, only the space inside the waveguides needs to be modelled. Once the individual components have been designed, they need to be assembled into a full system. This can introduce additional couplings and other effects which may detune the very sensitive elements slightly. To analyze the behavior of the whole system, the components can be combined within CST Studio Suite and reoptimized and simulated.
THE RESULT: HIGH-PERFORMANCE MICROWAVE COMPONENTS AND SUB-SYSTEMS
By using simulation to optimize their products, Apollo shortened the design process and lightened the workload of their engineers. Measurement results from prototypes of their couplers and power combiners agreed closely with the simulated results (Figure 3 and Figure 4), increasing confidence in the simulation process.
Figure 3 Comparison between experimental plots of the WR 28 4-way power combiner and numerical simulations with CST Studio Suite.
Figure 4 Comparison between experimental plots of the WR 112 triple cross-guide coupler and numerical simulations with CST Studio Suite for the coupling at each port.
With this semi-automatic workflow in place, Apollo’s engineers were able to turn their attention to the system and do what they do best: developing and manufacturing the components of tomorrow’s communication systems.