ISSTT Proceedings

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An Accurate Expression for the Input Impedances of One-Sided Microstrip Probes in Waveguide

Authors:
S. Withington, G. Yassin, J. Leech, K. G. Isaak
Abstract:
In previous work we established a general procedure for calculating the input impedances of one-sided microstrip probes in waveguide. The one-sided configuration, where the probe extends only part way across the waveguide, contrasts with the two-sided configuration, where the probe extends the whole way across the waveguide. We demonstrated that because of the way in which the different current distributions couple to the waveguide modes, the one-sided probe is intrinsically lower impedance and more broadband than the two-sided probe. This observation has important consequences for the design of THz SIS waveguide mixers. Previously, we had to make an approximation when evaluating the integral for the complex radiated power, and this led to a corresponding approximation in the final expression for the input impedance. We have now evaluated this integral rigorously, and we have shown that the original approximation breaks down to third order in the width of the probe, an effect we have seen experimentally. In this paper, we review the technique for calculating the impedances of one-sided microstrip probes, and we present a more accurate expression based on a rigorous analytical evaluation of the power integral. This expression is compared with complex impedances measured on a scale model at 5GHz, and excellent agreement is found.
Categories:
Circuits, Components
Year:
1999
Session:
10
Full-text:
Download a PDF of this paper.
Page Number(s):
508-518