Low-frequency Equipment Research Articles

Investigation and Modeling of Hot Carrier Effects on Performance of 45- and 55-nm NMOSFETs With RF Automatic Measurement

Effects of hot carriers on dc and RF reliabilities for both 45- and 55-nm negative metal-oxide-semiconductor field-effect transistors with in-line ground-signal-signal-ground test-pad structures were investigated in detail. The investigations were evaluated by an RF automatic testing system with a proprietary control program in Agilent's Integrated Circuit Characterization and Analysis Program software. After a hot carrier stress, we found that the increase in Cgs is larger than the decrease in Cgd for 55- and 45-nm devices, and the difference increases as the process technology keeps advancing. Thus, the degradations of cutoff frequency fT and maximum oscillation frequency fmax are dependent on transconductance gm and gate capacitance Cgg (= Cgs + Cgd) for 45- and 55-nm devices. This is different than many conventional studies that used low-frequency equipment. We propose a surface channel resistance model to comprehensively interpret the observations and verify it by the slope changes in the curves of measured fT versus gm.

Capacitance sounding: a new geophysical method for asphalt pavement quality evaluation

A capacitance sounding method has been proposed and developed for evaluation of the actual thickness and dielectric permittivity of asphalt pavement. The method is based on the continuous measurements of the electrical capacitance between two electrodes in real time. One of them is grounded within the soil immediately adjacent to the side of the road. Another one (sensing electrode) is mounted on a motor-driven positioner to obtain the capacitance measurements at multiple locations along the direction perpendicular to asphalt surface. The principle of the method is to vary the clearance of the sensing electrode to sound the 1D structure of the pavement beneath that electrode. A distinguished feature of the proposed technology is that the measured signal depends only on the thickness and the permittivity of the asphalt layer. All underlying layers do not affect the capacitance readings. A set of capacitance values versus sensing electrode positions is considered as a sounding curve. Software tools were created for solving forward and inverse problems of the capacitance sounding. An unknown thickness and permittivity are derived from a real-time inversion of the data obtained. Upon completing the inversion, an operator can move the assembling with the second electrode across the asphalt surface to the next sounding site. The capacitance sounding method proved to have a good lateral resolution: the dielectric permittivity values and the asphalt layer thickness are accurately detected over distances of 40 cm from a measuring point. An extensive feasibility study of capacitance sounding using both mathematical modeling and field measurements has been carried out. As a result, portable, low-frequency equipment has been designed and created. Asphalt layer thickness and the dielectric permittivity measurements were carried out on a high-traffic highway. The comparison of field trial results with core sampling analysis demonstrated the efficiency of the proposed method.

Through-The-Earth Radio Communications For Trapped Miners

Through-the-earth radio offers a possible means of communication with trapped miners after a mining disaster. Much of the original work was the outgrowth of war research. Since the 1920's the efforts to develop through-the-earth radio have paralleled developing electromagnetic geophysical techniques. The electrical characteristics of the earth medium as well as the ambient electromagnetic noise have been determined and theoretical models of electromagnetic propagation have been derived. Since 1969, under U.S. Bureau of Mines leadership, numerous researchers have tried to develop deployable systems. Despite some successes the basic problem remains unresolved. Low frequency signals must be used to penetrate the earth to a sufficient depth; but low frequency equipment is bulky, heavy, expensive and requires large power supplies which are not available to trapped miners. New techniques utilizing miniaturized circuitry and computers shows promise of providing a technology from which workable through-the-earth communication systems may develop in the near future.

940–960-megacycle communications equipment for industrial applications

Microwave equipment uses the same kinds of parts applied in the same general manner as in low-frequency equipment. However, because of the wide frequency spectrum available, realizable antenna gains, propagation characteristics, and economic considerations, microwave equipment is widely different from low-frequency equipment in design and application.