In-situ microwave measurements of lossy dielectrics
Abstract
The objective of this work has been to develop microwave (4.9 GHz) instrumentation systems, and measurement and inversion techniques for determining the complex dielectric constant of lossy media in-situ. Unique features of this work, compared to other studies, are that the complex propagation constants of traveling waves which are coupled to the medium under test are measured using phase-sensitive homodyne systems. An invasive method was studied wherein a small modulated scattering probe is inserted into a test hole in the medium, and the propagation constant of a spherically expanding wave originating outside the medium is measured. Results are given for portage sand vs moisture content. A non-invasive method uses an open-walled slotted rectangular waveguide laid directly on the surface to couple the traveling wave in the waveguide to the medium. The instrumentation and measurement techniques work quite well and results are given for several media, e.g., rock, concrete, sand, etc. A promising inversion method for finding the dielectric constant is presented, along with suggested improvements in the design of the traveling wave applicator and the detection instrumentation.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- January 1982
- Bibcode:
- 1982STIN...8224433K
- Keywords:
-
- Electrical Measurement;
- Lossy Media;
- Microwave Equipment;
- Permittivity;
- Dielectrics;
- Homodyne Reception;
- Moisture Content;
- Remote Sensors;
- Sands;
- Traveling Waves;
- Wave Propagation;
- Electronics and Electrical Engineering