Design of TEM Transmission Line for Probe Calibration up to 40 GHz

With the ongoing development of 5G wireless communication, frequencies as high as 40 GHz have become relevant for EMI near-field scanning. This paper describes the development process of two transmission lines with air dielectrics for probe calibration, namely a rod over ground plane and an air trace. Because of homogeneous dielectrics the transmission lines become almost pure TEM, which is preferable regarding probe calibration to a coplanar waveguide (quasi- Tem). The design process shows that at very high frequencies, transitions in the transmission line are critical and all small physical details must be included in the simulation model in order for it to be reliable.