Elisa Fratticcioli

A simple and low cost measurement system for the complex permittivity characterization of materials

A m A microwave planar resonanf sensor and the driving electronics for the measurement of fhe compler permitfivify in compact areas of the material under fesf (MUV is presented Compared to transmission or refecfion sensors, the adoprion of a scalar 2-porf measurement procedure reduces the cosf of fhe system and improves ifs robustness. The measuring sysfem requires on& fhe calculation of two paramefers, name& the resonant frequency and the 3dB bandwidth, thus achieving a subsfanfial reduction of cost and computafion rime. Such sensor can be adopted in moisfure measuremenf sysfems and ifs low cosf is such as fo allow is use even in a disposable monner.

A novel technique for complex permittivity measurement based on a planar four-port device

A novel technique for the measurement of the complex permittivity of materials is presented that overcomes many limitations of the conventional measurement methods. The RF signal transmitted through a transmission line loaded with the material under test is combined with a reference signal using a quadrature hybrid in such a way that the complex permittivity can be measured by simply detecting the two output amplitudes. This technique requires a simple calibration procedure, provides good accuracy, and avoids expensive vector measurements, thus combining the advantages of transmission methods, in terms of good accuracy, with those of resonant methods, in terms of scalar measurements. Two microstrip implementations have been realized for measurements at 2.35 and 10 GHz, showing very good accuracy to be achieved in both frequency ranges. The measured permittivities have been compared with those obtained with a resonant and transmission method and with data from literature, resulting in a very good agreement for both epsivr and tandelta

A planar resonant sensor for the complex permittivity characterization of materials

A microwave planar resonant sensor for the measurement of the complex permittivity in compact areas and thin layers of the material under test (MUT) is presented. Compared to transmission or reflection sensors, the adoption of a scalar 2-port measurement procedure reduces the cost of the system and improves its robustness. Compared to coaxial line sensors, a substantial cost reduction is achieved. The low cost of the sensor allows its use even in a disposable manner. Through the fullwave characterization of the probe a simple equivalent semilumped model of the interaction with the MUT has been derived along with a software calibration procedure. An excellent measurement accuracy in a wide range of complex dielectric permittivities is shown to be feasible.

A new permittivity model for the microwave moisture measurement of wet sand

A new mixing model for the dielectric constant of wet powdered materials is presented. By an accurate calibration the model allows the computation of the moisture content of wet powdered materials. Moisture determination is based on permittivity measurements by a microwave resonant sensor developed in a previous work. The results of silica sand measurements show that an accuracy of ±1% in moisture content can be obtained. The measurement procedure is easy and fast; it can be performed in real time and even in an industrial environment

An Accurate and Low Cost Complex Permittivity Measurement System Using a Planar Resonant Sensor

A microwave planar resonant sensor for the measurement of the complex permittivity in compact areas of the material under test (MUT) is presented. Both thin and thick samples can be considered. Compared to transmission or reflection sensors, the adoption of a scalar 2-port measurement procedure reduces the system and improves its robustness. The measuring system requires only the calculation of two parameters, namely the resonant frequency and the 3dB bandwidth, thus achieving a substantial reduction of cost and computation time. The low cost of the sensor is such as to allow its use even in a disposable manner.

A novel technique for complex permittivity measurement based on a planar four port device

A novel four port device for complex permittivity measurement is presented consisting of the cascade of two 3 dB branch line directional couplers connected through two U-shaped transmission line lengths. The material under test (MUT) is brought into contact with one U-shaped section. The complex dielectric permittivity of the MUT is evaluated by simply measuring the amplitudes of the two outputs, thus obtaining a simple and cheap measurement procedure. A prototype has been fabricated and experimentally tested exhibiting very good accuracy.

A Novel Technique for Measuring One-Dimensional Permittivity Profiles Using a Simple Non-Commensurate Planar Structure

A novel technique is presented for measuring one-dimensional permittivity profiles based on a simple planar structure. The measuring device consists of a transmission line loaded with open-ended stubs of non-commensurate lengths. The permittivity profile of the material under test is evaluated by simply measuring the attenuation pole frequencies in the transmitted RF signal due to the different loaded stubs. The proposed technique provides reliable results for both continuous and discontinuous permittivity profiles without requiring any a priori information of the unknown profile. Measurements using different materials have been performed resulting in good agreement with data from the literature.

A Low-Cost Driving Circuitry for Permittivity and Moisture Measurement Systems

The implementation of a low cost driving electronic for a permittivity measurement system employing resonant microwave sensors is presented in this paper. The complete driving electronics needed to perform scalar measurements is described and its components are illustrated and characterized. The measurement results and accuracy have been compared with commercial devices showing similar performances

Monitoring moisture content in composting systems using a planar resonant sensor

A microwave planar resonant sensor for the measurement of moisture content in composting piles is presented. Compared to the classical oven-dry method, the use of a microwave sensor allows real time measurement. The measuring system requires only the calculation of two parameters, namely the resonant frequency and the 3 dB bandwith, thus achieving a substantial reduction of cost and computation time. The influence of the sample density on the measured parameters has been investigated.

Dual-Band Permittivity Measurement of Thin Dielectric Layers with a Simple Planar Device

An improvement of a method for permittivity measurement is introduced based on a dual-band four port planar structure, consisting of two cascaded cross-coupled quadrature hybrids connected through two transmission lines. The applicability of the method to permittivity measurement of thin dielectrics is then demonstrated: permittivity are evaluated at two different frequencies f0 and n*f 0 (n=1,2,3..) by simply detecting the two output amplitudes, thus avoiding any phase measurement and allowing a remarkable space reduction. A prototype has been fabricated in microstrip technology and experimentally tested exhibiting very good accuracy for permittivity measurement at two different frequencies spaced by an octave band