Many of the current 5G applications require the use of isotropic materials.  This simplifies the design process and limits performance dependencies and variations associated with anisotropic materials like woven glass fiber epoxy-based substrates.  Because of this many metrologies, despite having different characteristics with respect to in-plane and out-of-plane measurement sensitivities, produce bulk material results that are largely interchangeable for mmWave applications. 

As mmWave frequencies become more routinely used, there will be a drive to design on lower cost materials, many of which may be anisotropic.  This effect can be seen historically - decades previously considered single digit GHz design advanced and utilized expensive isotropic substrate materials.  Today high-speed interconnects with multi-GHz bandwidths are routinely used in computers to link chips through low-cost, anisotropic substrates.

Additionally, in the future very advanced designs may be able to utilize specifically designed anisotropic materials in new ways.  For example, it may be possible to utilize a planar material having a significantly different permittivity along one axis to produce antenna designs that are better optimized for a given application. 

If this happens there will be an increased need to be able to accurately characterize the anisotropic behavior of these materials.  This may drive the need for new measurement  tools and methods.

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.

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