Practical Diversity Design for PCB IoT Terminals

Mobile or nomadic diversity antennas feature a variety of element types and layouts, mostly PCB-based, reflecting complex design trade-offs between their performance and the required compactness. The design stage is electromagnetic-based but must include several signal-based diversity metrics, and there is a shortfall of information about their assumptions and the impact of their violation. The evaluation stage normally includes simulation, with physical measurements being the bottom line. Pattern measurement is particularly challenging, but accurately measured patterns are critical parameters, enabling the calculation of mean gains and correlations, and the impact of different propagation scenarios. For developers, the complex set of processes for design and evaluation make it difficult to have confidence with their in-house procedures without access to independent results for a variety of antenna types. For the design stage, we review and clarify the diversity metrics, and for evaluation, a set of typical and new diversity designs implemented on printed circuit board (PCB) are also presented. The methods cover lossy antennas and the expected performance in a directional propagation scenario. This information helps designers and developers to better understand the design process and to check their evaluation procedures.