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Microwave Power Absorption in Low-Reflectance, Complex, Lossy Transmission Lines



Jon Geist, Jayna J. Shah, Mulpuri Rao, Michael Gaitan


Simple sets of equations have been derived to describe the absorption of microwave power in threeregion, lossy transmission lines in terms of S-parameter reflection and transmission amplitudes. Each region was assumed to be homogeneous with discontinuities at the region boundaries. Different sets of equations were derived to describe different assumptions about the amplitudes of the reflection coefficients at the different boundaries. These equations, which are useful when interference effects due to multiple reflections are small, were used to analyze S-parameter measurements on a transmission line that had a microfluidic channel in its middle region. The channel was empty for one set of measurements and filled with water for a second set of measurements. Most of the reflection assumptions considered here produced similar results for the fraction of the applied microwave power that was absorbed by a waterfilled microchannel. This shows that the absorbed power is relatively insensitive to the reflection details as long as energy is conserved in the analysis. Another important result of this work is that the power absorbed in the water-filled channel can be much larger than the difference between the power absorbed when the channel is full of water and that when the channel is empty.
Journal of Research (NIST JRES) -


absorption, microchannel, microfluidic device, microwave, transmission line.


Geist, J. , Shah, J. , Rao, M. and Gaitan, M. (2007), Microwave Power Absorption in Low-Reflectance, Complex, Lossy Transmission Lines, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed March 5, 2024)
Created July 31, 2007, Updated October 12, 2021