The sections in this article are


1
Radiometers

2
Radar Scattering

3
Radar Scatterometers

4
Radar Altimeters

5
Ground-Penetrating Radars

6
Imaging Radars

7
Real-Aperture Radars

8
Synthetic-Aperture Radars

Microwave Remote Sensing

This paper is the second in a series evaluating the microwave dielectric behavior of vegetation material. It draws upon the data presented in Part I to develop a Debye-Cole dual-dispersion dielectric model consisting of a component that accounts for the volume fraction occupied by water in free form and another that accounts for the volume fraction occupied by the mixture comprised of water molecules bound to bulk-vegetation molecules. To determine the dielectric dispersion properties of the latter, measurements were made for sucrosewater solutions of known volume ratios. The proposed dielectric model is found to give excellent agreement with data over a wide range of moisture conditions and over the entire 0.2-20 GHz range examined in this study.

Microwave Dielectric Spectrum of Vegetation - Part II: Dual-Dispersion Model

This paperisthesecond inaseries evaluating themicro- wavedielectric behavior ofvegetation material. Itdrawsuponthedata presented inPartItodevelop aDebye-Cole dual-dispersion dielectric model consisting ofacomponent thataccounts forthevolume fraction occupied bywaterinfreeformandanother thataccounts forthevol- umefraction occupied bythemixture comprised ofwatermolecules boundtobulk-vegetation molecules. Todetermine thedielectric dis- persion properties ofthelatter, measurements weremadeforsucrose- watersolutions ofknownvolume ratios. Theproposed dielectric model isfoundtogiveexcellent agreement withdataoverawiderangeof moisture conditions andovertheentire 0.2-20 GHzrangeexamined inthis study. I.INTRODUCTION

Microwave Dielectric Spectrum ofVegetation PartII:Dual-Dispersion Model

This paper summarizes the progress achieved in the active microwave remote sensing of soil moisture during the four years of the AgRISTARS program. Within that time period, from about 1980 to 1984, significant progress was made toward understanding 1) the fundamental dielectric properties of moist soils, 2) the influence of surface boundary conditions, and 3) the effects of intervening vegetation canopies. In addition, several simulation and image-analysis studies have identified potentially powerful approaches to implementing empirical results over large areas on a repetitive basis. This paper briefly describes the results of laboratory, truck-based, airborne, and orbital experimentation and observations.

/pdf/active-microwave-soil-moisture-research-2yzspks48x.pdf

Active Microwave Soil Moisture Research

1 Introduction- 2 Ionizing Radiation Computed Tomography- 3 Thermal Imaging- 4 Microwave Imaging- 5 Ultrasonic Imaging- 6 Nuclear Magnetic Resonance- 7 Neutron Imaging- References- List of Notations- Color Plates

Nondestructive Characterization and Imaging of Wood

Three waveguide transmission systems covering the 1-2, 3.5-6.5, and 7.5-8.5 GHz bands were used to measure the dielectric properties of vegetation material as a function of moisture content and microwave frequency. The materials measured included, primarily, the leaves and stalks of corn and wheat. Dielectric measurements also were made of the liquid included in the vegetation material after it was extracted from the vegetation by mechanical means. The extracted liquids were found to have an equivalent NaCl salinity of about 10 per mil, which can have a significant effect on the dielectric loss at frequencies below 5 GHz. The results of attempts to model the dielectric constant of the vegetation-water mixture in terms of the dielectric constants and volume fractions of its constituent parts (i. e., bulk vegetation, air, bound water, and free water) are discussed. Additionally, measurements of the temporal variations in the total attenuation at 10.2 GHz are presented for a corn canopy and a soybean canopy.

Microwave Dielectric Properties of Plant Materials

Three waveguide transmission systems covering the1-2, 3.5-6.5, and7.5-8.5 GHzbandswereusedtomeasurethedielectric properties ofvegetation material asafunction ofmoisture content and microwave frequency. Thematerials measured included, primarily, the leaves andstalks ofcornandwheat. Dielectric measurements also were madeoftheliquid included inthevegetation material after itwasex- tracted fromthevegetation bymechanical means.Theextracted liquids werefoundtohaveanequivalent NaClsalinity ofabout10permil, whichcanhaveasignificant effect onthedielectric loss atfrequencies below5GHz.Theresults ofattempts tomodelthedielectric constant ofthevegetation-water mixture intermsofthedielectric constants and volumefractions ofits constituent parts (i.e., bulkvegetation, air, bound water, andfreewater) arediscussed. Additionally, measurements of thetemporal variations inthetotal attenuation at10.2GHzarepre- sented foracorncanopyandasoybean canopy. I.INTRODUCTION FROM THEstandpoint ofwavepropagation, avegetation canopy isadielectric mixture consisting ofdiscrete dielec- tric inclusions (leaves, stalks, fruit, etc.) distributed inahost orbackground material suchasair. Inmostcanopies, thesizes oftheinclusions arecomparable toorlarger thanthewave- length inthemicrowave region, which meansthat thecanopy

R. P. Jedlicka

Papers

Microwave Dielectric Properties of Plant Materials

MicrowaveDielectric Properties ofPlantMaterials