Guest post by Thomas Sickel, Lead Antenna Design Engineer of Magus (Pty) Ltd.
Antenna Magus is an antenna synthesis tool, developed to help engineers design efficient RF devices. Its database, currently consisting of 225 antennas, can be explored and searched to find the optimal antenna topology for the given problem. This topology can then be designed and tuned to meet the system requirements, and subsequently exported as a fully parametric, ready-to-run 3D model compatible with CST MICROWAVE STUDIO® (CST MWS), allowing Antenna Magus to integrate seamlessly in the design workflow.
A basic performance analysis is available inside Antenna Magus, but a full 3D simulation is often necessary to obtain a more complete and more accurate solution. This is especially useful in cases where multiple devices require simultaneous simulation in an assembled, compound device. While CST DESIGN STUDIO™ (CST DS) may be used to perform a linear analysis on such a system, the effects of the more complex electromagnetic interactions between the various components will only become apparent in a full 3D simulation of the assembled device in CST MWS.
The example illustrated here is a combined GSM and WLAN monitoring system, covering a frequency range between 698 MHz and 5.855 GHz. Using Antenna Magus, a suitable antenna element is found to be the circularly polarized, UWB, absorber-lined cavity-backed Archimedes spiral antenna, and the coax-to-parallel wire transition is found to be a suitable transition / balun used to feed the spiral. The transition is designed for a number of electrical and mechanical specifications. An impedance match between the 50 Ω input and the 188 Ω spiral resistance is required, and the model needs to comply with certain manufacturing restrictions, including dielectric properties and an outer diameter requirement to match an SMA connector. Some commonly used RF coaxial connectors, such as an SMA 2 hole female panel mount with extended PTFE used here, are also available in Antenna Magus.
Once all the devices have been exported from Antenna Magus, they can be combined in CST DS for a linear cascaded analysis or in CST MWS for a full 3D simulation. The figure below shows a good agreement between the linear solution (red) and the full wave solution (green). This indicates that in this particular instance, the interaction between devices was negligible and as a first-order approach, the compound structure may be successfully analyzed using the substantially quicker linear solver.
System Assembly and Modeling (SAM) in CST STUDIO SUITE® could be used to optimize and analyze the structure further, and allow the engineer to include steps such as thermal analysis to investigate the heat dissipation of the absorbing layers inside the cavity. This means that a broad multiphysics analysis of the entire system can be carried out using only Antenna Magus and CST STUDIO SUITE.