Recent interest in communication and sensing at millimeter wave frequencies has led to a need for accurate characterization of dielectric materials for antennas and components. Historically, broad-band free space methods have suffered from poor accuracy when determining the loss tangent of very low-loss materials.
This paper provides several new corrections that improve the loss tangent accuracy of these methods by over an order of magnitude. Specifically, corrections that account for beam shift and focusing effects are described and demonstrated on several dielectric materials known for their low loss. These corrections are demonstrated on both focused beam and non-focused, free-space probe measurements.
