Permittivity and loss tangent measurements at mmWave have a number of intrinsic challenges:
Variations over temperature and humidity. Material behavior under moisture absorption is often a concern for high volume industrial applications. Techniques that are slow or require lengthy procedures may limit a user’s ability to evaluate materials against moisture absorption. For many thin (< 100 um) substrate materials, sufficient moisture absorption or drying can occur over the course of 10 minutes to alter the performance of the material. Hence, methods that allow for samples to be quickly configured in the test equipment, with minimal alignment requirements and speedy data collection are desirable.
Most available measurement solutions are resonant methods, but continuous frequency characterization is needed.
See also the need for tighter dimensional specifications due the higher frequencies with mmWave:
Higher frequencies for 5G result in requirements for lower dimensional variation and measurement errors
As part of the 5G/6G MAESTRO project, work on this page is supported by the Office of Advanced Manufacturing in the National Institute of Standards and Technology (NIST), under the Federal Award ID Number 70NANB22H050.