Performance and reliability of a 5G smartphone RF-antenna system: Influence of temperature field

The last decade has seen a rapid evolution of wireless systems and smart devices. The advent of fifth generation (5G) wireless standards in the near future will undoubtedly accelerate the pace of this advance. 5G wireless presents a new challenge in that its devices must be scalable to a mass commercial market at suitably low costs. Thus, a significant tradeoff must be made between performance and cost — more so than was necessary for many previous generations of mm-wave devices. Simulation will become increasingly more important in helping to balance this tradeoff in a multitude of mass-produced 5G devices. This paper presents a simulation workflow and case study that illustrates the importance of a comprehensive multi-physics approach to designing wireless systems, with a view towards expected developments in future 5G and mm-wave designs. The electrical performance of the antenna under “ideal” (i.e. room-temperature) conditions is determined first. The electromagnetic (EM) results are then incorporated in a thermal analysis to determine the spatial variation of steady-state temperature when the amplifier and antenna are in a constant “on” state. The thermal solution is then fed back to the EM simulation to re-compute the antenna's electrical performance under the influence of radio frequency (RF) heating. The key in this last step is to not only account for the temperature-dependent material properties of the 3D model via spatially-varying thermal feedback, but also to account for the temperature dependent properties of the components in the driving circuit schematic. This comprehensive multi-physics approach shows the true potential for performance degradation of the antenna transmitting system. In particular, the effect on the important antenna performance metrics of impedance match, radiative efficiency, and tuned resonant frequency are considered.