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An Investigation of the Input Impedance of a Microstrip Probe in Waveguide.

Authors:
S. Withington, G. Yassin
Abstract:
We derive an expression for the input impedance of a one-sided microstrip probe in waveguide. By "one-sided" we mean an insulated probe that extends only part way across the waveguide. This arrangement contrasts with the "Eisenhart and Kahn" or "double-sided" configuration, where the probe extends the whole way across the waveguide and is earthed at both ends. Our analysis is based on the spectral-domain method and is able to take into account the dielectric substrate on which the thin-film antenna is deposited. In submillinietre-wave components, the thickness of the substrate is 10-20% of the width of the waveguide, and the substrate has a significant effect on performance. We have examined the validity of our model by carrying out extensive impedance measurements at 5G-Hz. A key feature of the paper is that we compare the general characteristics of the one-sided probe, in the context of SIS mixers, with those of the two-sided probe. We show that the bandwidth of a probe that stretches only part way cross the waveguide is very much greater than the bandwidth of a probe that stretches all of the way across the waveguide. Moreover, the input resistance is lower and more suited to SIS tunnel junctions. We also show, analytically, that the input impedance is almost independent of axial orientation.
Categories:
Devices, Waveguides
Year:
1997
Session:
7
Full-text:
Download a PDF of this paper.
Page Number(s):
326-343