Transmission Line Measurements

Prior to measurement, a two-port thru calibration is performed wherein the references planes were shifted to the inner edges of the 31-mil FR4 transmission line. Measurements are performed in the power range of 24--47 dBm at 2.1GHz with the diamond bridges mechanically actuated in addition to the applied DC voltage. 

In porous layers, the influence of Rc may be minimized because it will be connected in series with a large number of resistances, typically thousands, which may have comparable values. Transmission line measurements (TLMs) performed with thick Sn02 layers exposed to CO and NO2 did not result in values of Rc clearly distinguishable from the noise, while in the case of thin films the existence of Rc was proven. Again, the relative importance played by different terms may... 

When a control system is being used, the designer must indicate the transmission lines that will connect the measuring element to the final control element. The notation for these transmission lines is given in Table 7-3. The final control element has the same code letters and numbers as the controller that regulates it, plus an additional letter to indicate whether it is a valve, switch, or other device. 

Hoefer, U. Steiner, K. Wagner, E. Contact and sheet resistances of Sn02 thin films from transmission line model measurements. Sensors and Actuators B (1995), p. 59-63. 

Before conducting electric blasting operations in the vicinity of power transmission lines, it is advisahle to check (in the presence of power company representative) for ground currents. Also it is advisable to determine whether or not measurable voltages can become more hazardous when peak power levels are transmitted. To conduct these... 

MEASUREMENT OF DIELECTRIC PROPERTIES 3.1. Transmission Line Techniques... 

Hippel 1954b). The values of e and e" were derived from microwave theory by placing a sample of material against the end of a short-circuited transmission line, such as a waveguide or a coaxial line. This technique has applicability to high and low loss materials and in the present day has found applicability for the measurement of powders, grains and pulses (Nelson 1972,1991). 

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. 

The unit works on the principal that the microwave attenuation of a strip transmission line depends upon the loss factor of the material with which it is in contact. Data indicates accuracies of 5% can be attained by the hand-held instruments, depending upon the range of fat measured. The instruments sell for approximately 5000.00. Copies of references are available from Distell. 

Topp, G. C., Davis, J. L., and Annan, A. P. (1980). Electromagnetic determination of soil water content Measurements in coaxial transmission lines. Water Resources Research, 16(3), 574-582. 

THz spectroscopy was born from research efforts to produce and detect ultra-short electrical currents as they traveled down a transmission line.26 In 1988-1989, it was discovered that electromagnetic radiation pulses produced by time-varying current could be propagated through free space and picked up by a detector.27 By placing a sample between a THz source and detector, one could measure the differences in radiation pulses due to scattering or absorption by the sample to understand its chemical properties. 

In general, the quantities being determined by microwave measurements are complex reflection and transmission coefficients or complex impedances normalized to the impedances of the transmission lines connecting a network analyser and the device-under-test (dut). In addition to linear frequency domain measurements by means of a network analyser the determination of possible non-linear device (and thus material) properties requires more advanced measure-... 

Non resonant techniques are only of limited use to determine microwave losses with high precision, in particular when the losses are very small. Flowever, for the investigation of nonlinear absorption phenomena (i.e. rf power dependent on surface impedance or loss tangent) by intermodulation distortion measurements broad-band test devices are more common. Typically, a planar transmission line with an impedance of 50 Ohms can be employed for intermodulation... 

Figure 10. Nyquist plot of the impedance spectrum experimentally measured on the ACFCE at an applied potential of 0.1 V (vs. SCE) in a 30 wt % H2SO4 solution. Dotted and solid lines represent the impedance spectra theoretically calculated based upon the transmission line model (TLM) in consideration of pore size distribution (PSD) and pore length distribution (PLD), respectively. Reprinted with permission from G. -J. Lee, S. -I. Pyun, and C. -H. Kim, J. Solid State Electrochem., 8 (2004) 110. Copyright 2003, with kind permission of Springer Science and Business Media.

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