Complementing the more commonplace SPDR and SCR techniques is the balanced-type circular disk resonator (BCDR). The technique works by sandwiching a metal disk between the two dielectric plates under test and inserting the sandwich between two parallel conductor plates, creating a region where there are multiple standing waves that resonate at different frequencies.

Figure 1: Schematic diagram of a commercial balanced circular disk resonator.


  • BCDR is particularly well-suited for high frequency measurements because the maximum measurable frequency is only limited by the coaxial lines used to excite the resonator, the apertures of the excitation holes, and other factors.

  • Unlike many of the other techniques, it can be used to measure multiple points between 10 GHz to 120 GHz.


  • The approach requires a 2-port network analyzer and a calibration kit in order to work.

  • The dielectric plates must be identical. They also must have the same thickness and smooth surfaces. This is challenging with non-commercial materials.

This method is under standardization in IEC project 63185.1 The standardized method is applicable for the measurements in the frequency area from 10 GHz to 120 GHz. 


  1. IEC TC 46/SC 46F - RF and microwave passive components, “Measurement of the complex permittivity for low-loss dielectric substrates balanced-type circular disk resonator method,” IEC 63185:2020, 8 December 2020.


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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