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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Quality and Safety Assessment Research Unit » Research » Publications at this Location » Publication #340147
Title: Open transverse-slot substrate-integrated waveguide sensor for biomass permittivity determination

Author
item MCKEOWN, MURAT - University Of Georgia
item JULRAT, SAKOL - Oak Ridge Institute For Science And Education (ORISE)
item Trabelsi, Samir
item TOLLNER, E - University Of Georgia

Submitted to: IEEE Transactions on Instrumentation and Measurement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2017
Publication Date: 8/4/2017
Citation: Mckeown, M.S., Julrat, S., Trabelsi, S., Tollner, E.W. 2017. Open transverse-slot substrate-integrated waveguide sensor for biomass permittivity determination. IEEE Transactions on Instrumentation and Measurement. 66(8):2181-2188.

Interpretive Summary: Energy production from biomass has grown substantially in recent years. Current policies in the European Union requiring renewable and low emission sources of energy have driven demand for fuel pellets derived from solid biomass in the United States. Solid biomass can be formed from the waste products of many different natural and manufactured products, including sawdust from lumber mills. Moisture content of sawdust is an important factor in determining its behavior in handling, pelleting, and value determination. Dielectric properties are those electrical characteristics of materials that determine their interaction with electric fields, and they have been found useful for sensing the moisture content of such materials. New techniques are needed for sensing or measuring the dielectric properties of materials to improve or provide moisture-sensing equipment for practical applications in agriculture and related industries. This paper describes studies on use of a new technique and type of device for sensing the microwave dielectric properties of sawdust from which moisture content can be rapidly determined. It involves microwave substrate-integrated waveguide components fabricated from double sided substrate material (sheet of dielectric material copper-clad on both sides) similar to PC cards. A novel open transverse-slot substrate-integrated waveguide sensor designed and fabricated for dielectric properties measurements on sawdust at 8 GHz was developed. Different configurations of the sensor were investigated by using simulation software. The sensor uses an open transverse slot to sense the dielectric properties of materials placed in contact with the waveguide slot. The technique proposed in this paper allows one to determine the moisture content of sawdust from measurement of the dielectric constant or the dielectric loss factor determined from measurement of reflections from the new microwave sensing device at a single frequency. Moisture contents of sawdust samples were determined form the dielectric constant or loss factor with high coefficients of determination. The reflection-based algorithms, coupled with the low cost of the sensing device, shows potential for use of this method for in-process moisture determination in sawdust during the pelleting operation where moisture content ranges from 8% to 20%. These findings support further work aimed at implementing a microwave moisture meter in an industrial pelleting process, providing benefits for the biomass industry and consumers of biomass products.

Technical Abstract: A novel open transverse-slot substrate-integrated waveguide sensor is presented. The sensor is designed and fabricated for dielectric poperties measurements on sawdust at 8 GHz. Different configurations of the sensor were investigated by using simulation software and relationships between the simulated magnitude and phase of the reflection coefficient and dielectric properties. A suitable configuration was fabricated with a circuit board milling machine, and the performance was investigated through measurements of the magnitude and phase of the reflection coefficient from sawdust samples. The permittivity of the material was determined by fitting the voltage standing-wave ratio and phase with a normalized two-dimensional polynomial with known dielectric properties values. The permittivity determination model was tested by using independent sets of training and validation measurements on sawdust at different bulk densities and moisture contents between 6.8% and 39%. The predicted dielectric properties values showed linear relationships with moisture content. Therefore moisture content in sawdust can be determined from measurements of either dielectric constant or loss factor at a single microwave frequency without knowledge of the bulk density.