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40 The PCB Magazine • July 2016 resonator does not work as a simple function of resonant frequency shifts from an unloaded to a loaded cavity. The resonator is a copper strip- line and only functions with the material under test placed in the fixture therefore has no free space baseline for relative comparison. The ba- sic calculations for ɛ r and tan δ are shown in the following equations: where and where and The quality factor of the cavity with sample (Q s ) is easily calculated using the above equa- tions and the measured resonator values. How- ever, the quality factor of the unloaded cavity (Q c ) is not so readily determined. The analytical approach is detailed in IPC-TM-650-2.5.5.5.1 as is the method for calculating the effective in- crease in resonator length from fringing field. This study considered nine, and in some in- stances 10, resonant frequencies in the 1 GHz to 22 GHz band. The measured values of ɛ r and tan δ were obtained for each sample and were aver- aged for comparison. The dielectric under test is presumed to be a single block on either side of the copper strip. Generally 60 mils [1.524 mm] is preferred as in IPC-TM-650 2.5.5.5. In this case, 5 mil [0.127 mm] material was sup- plied and stacked so the resulting ɛ r values are skewed lower due to entrapped air from incon- sistent thicknesses and embedded copper sur- face roughness pockets associated with cladding removal. PCB Editors note: Due to the length of this article, we have chosen to publish the Results, Conclusion, Acknowledgements and References at this location. *Co-Authors: Glenn Oliver is senior engineer with DuPont. Jonathon Weldon is RF applications engineer with DuPont CPM. Chudy Nwachukwu is financial cost engineer at Intel (formerly with Isola). John Andresakis is director of technical marketing for Park Electrochemical. John Coonrod is market development engineer with Rogers Corporation. David L. Wynants Sr., is company engineer with Taconic Advanced Dielectric Division. Don DeGroot is with Connected Community Networks. ROUND ROBIN OF HIGH-FREQUENCY TEST METHODS BY IPC-D24C TASK GROUP (PART 1)