Transmission line method measurements

Makela et al. [875] carried out detailed studies of the EMI-SE properties of 1 to 30 /im thick camphor-sulfonic-acid-doped P(ANi) films having conductivities in the 10 to 100 S/cm region. Measurements were carried out in the near-field with a dual chamber, and in the far-field using a transmission line method, in 0.1 MHz to 1 GHz region. A strong correlation with surface film resistivity was found. Multi-layered structures were found to enhance shielding considerably, up to 40 dB at 100 MHz to 1 GHz. Fig. 19-3 summarizes some of their results in the near and far field. 

The refractive index, n, may be measured using an optical microscope [1,2,23,27,34]. Phase contrast increases the contrast due to differences in n and allows a more accurate determination. Interference contrast in transmission gives the optical path length and the average refractive index through the specimen thickness [1], The Becke line method gives the surface refractive index [1],... 

A method which circumvents many of the disadvantages of the transmission line and cavity perturbation technique was pioneered by Stuchley and Stuchley (1980). This technique calculates the dielectric parameters from the microwave characteristics of the reflected signal at the end of an open-ended coaxial line inserted into a sample to be measured. This technique has been commercialized by Hewlett Packard with their development of a user-friendly software package (Hewlett Packard 1991) to be used with their network analyzer (Hewlett Packard 1985). This technique is outstanding because of its simplicity of automated execution as well as the fact that it allows measurements to be made over the entire frequency spectrum from 0.3 MHz to 20 GHz. 

Despite the first presentation of the network analyser in 1965, the large-band measurement techniques only appeared in 1974. After ameliorations on the accuracy and the development of Von Hippel s methods, the first data treatments were proposed. Weir [III] and Nicholson [112] used the reflection and transmission coefficients (S parameters) resulting when a test sample was inserted into a waveguide or a TEM transmission line as shown in Figure 8.7 From measurements, complex permittivity and permeability values were derived in the range from 50 MHz to 18 GHz. 

In [22] a frequency-independent RLGiC parameter for the transmission lines is modeled for the transmission line and the wave-splitting and Green functions techniques are applied to reconstruct the transmission line. The losses of the conductor and dielectric and the frequency dependence of the parameters of the transmission line are neglected, so that this method is not accurate and is suitable for wire fault location only in a simple transmission lines. The transmitted signal is measured to restore the parameters of the transmission line. For that a measurement from both sides is necessary. 

Salt purity, density, chemical composition, and other properties. In the laboratory, high-temperature salt properties are measured by spectroscopy. Laser or other light is sent through the salt, and the transmission of the light is measured as a function of frequency. In more sophisticated systems, secondary emission lines are measured. Salt impurities that can be measured to very low concentrations include uranium, the actinides, iron, chromium, and nickel. The chemical valence state can also be measured. This is likely to be the preferred method for monitoring the concentration of impurities and the redox potential of the salt and thus the performance of the salt cleanup systems. It would be the equivalent of the instrumentation used to monitor water chemistry in an LWR. 

Several techniques are available for determining the current distribution including transmission line approximations, the method of moments (MoM) and measurements. 

A key element of PEM fuel cell is the CCL, which contains a double layer capacitance connected to resistivities due to proton and oxygen transport. To understand measured CCL spectra, many works employ the equivalent circuit method (ECM). This method is based on the construction of an equivalent transmission line, which gives an EIS spectrum close to the spectrum of the system of interest. The components of the resulting circuit are then attributed to CL physical parameters. For example, in a recent work, Nara et al. (2011) used the ECM to study the CCL degradation mechanisms in the PEFC. 

The method is based on the compensation of phase change due to the microwave energy absorption of the liquid sample. The short circuit piston situated behind the sample must be actuated for compensation. The energy conditions created by the wave front in the waveguide are measured by four diode-detectors. Based on the diode detector signals the wave-front pictures are developed in the transmission-line as it is represented on Figure 2. As it shown, essentially three arrangements can be formed. 

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