Development of a 100 GHz Grooved Circular Empty Cavity for Complex Permittivity Measurements in W Band

Yoshinori KOGAMI

IEICE TRANSACTIONS on Electronics   Vol.E94-C    No.10    pp.1650-1656
Publication Date: 2011/10/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.1650
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Microwave and Millimeter-Wave Technology)
Category: Measurement Techniques
cavity resonators,  millimeter wave measurements,  dielectric measurements,  cut-off circular waveguide method,  

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A 100 GHz grooved circular empty cavity is proposed for the low loss dielectric substrate measurements by the cut-off circular waveguide method in W band. The influence of the excitation holes for the coaxial cable with a small loop are revealed by an FEM based 3D electromagnetic simulator. And also, the diameter of the excitation hole is determined based on the calculated results and the manufacturing accuracy. Then, two kinds of four 100 GHz grooved circular empty cavities are fabricated. Comparative experiments of the cavities with the different excitation holes validate the simulated results. Moreover, the complex permittivity of a PTFE plate is measured using the fabricated four cavities by the cut-off circular waveguide method around 84 GHz. The measured results agree within measurement error about 0.5% for εr and 5% for tanδ. Also, these results accord with results measured by the Whispering-Gallery mode resonator method in 85–110 GHz band. It verifies that the proposed 100 GHz cavity for the cut-off waveguide method is useful for the complex permittivity measurement of low loss dielectric substrates in W band.