Open-Wire Transmission Lines Applied to the Measurement of the Macroscopic Electrical Properties of a Forest Region
Special technical rept.
STANFORD RESEARCH INST MENLO PARK CA
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The theoretical capabilities of two-conductor, open-wire transmission lines OWLs as probes to measure the macroscopic electrical properties of a forest are examined under the premise that a forest can be represented as a lossy dielectric slab. A laboratory experiment with a line inserted in a relatively homogeneous, isotropic slab of Styrofoam was performed to verify certain approximations in the analysis of such a line when a void hole exists in the slab near the line. The effective sensing radius for a 300-ohm line is shown to be about one and one-half line spacings. The limitations of a transmission-line probe for inhomogeneous and anisotropic dielectrics are discussed. The forest also is considered as a synthetic dielectric composed of lossy scatterers. The equivalent circuit of a short scatterer length small relative to the RF wavelength as a load on the transmission line is shown to be a lossy capacitor.
- Radiofrequency Wave Propagation
- Radio Communications