Recent trends and developments, such as 5G deployment, massive MIMO and beamforming, automotive radar, and space applications, are shaping the field of RF communications of the 21st century, particularly in the context of millimeter waves. Designing traditional passive components at millimeter wave frequencies brings new challenges due to their small size, manufacturing tolerances, material selection, and other factors. In this article, the concept of a conventional surface mount planar Wilkinson power splitter is revisited and examined at frequencies above 20 GHz. The advantages and disadvantages of various surface mounting configurations were discussed, focusing on easy installation and repeatable RF performance.
The paper also presents some of the design recommendations toward the miniaturization, compactness, and geometrical efficiency of the Wilkinson power splitters. Combining Wilkinson two-way splitters of various power ratios into more complex power distribution networks is a tedious task that requires layout customization and careful tuning of basic RF building blocks. These design considerations are described on the example of a 4-way Wilkinson splitter on alumina substrate for operational frequency band 25 – 35 GHz. The design prototypes have been successfully produced and tested with the results presented in this article.