Application development in the millimeter-wave (mmWave) frequencies for terrestrial communication, high-frequency device characterization, automotive radar, and other technologies is increasing. The challenge of testing and characterizing the devices that enable new solutions is becoming increasingly complex. As broadband testing over hundreds of gigahertz of bandwidth is subject to repeatability and accuracy deficits, researchers and engineers are demanding better broadband solutions that help to overcome these challenges and simplify mmWave testing.