Characterization and performance prediction for integral resistorsin low temperature co-fired ceramic technology

This paper addresses the electrical characterization of integral resistors in low temperature co-fired ceramic (LTCC). The resistors form part of an integral component technology that also includes capacitors and inductors. The geometry and fabrication of the integral resistors is summarized, describing a screen-printing method that places the resistors 200 μm into the substrate. A test vehicle made to analyze the technique, 150 samples of which were characterized, is described. Three different resistor pastes are analyzed; 104 Ω/sq, .66 kΩ/sq, and 6.2 kΩ/sq. In addition, further parameters are investigated, including the effects of lamination pressure, resistor size, and the use of trim-holes in the technology. The results of the analyzes are summarized with regard to the impact of applied frequency, temperature, and DC voltage. The paper then discusses the development of performance predictive functions for the variations in the resistors, functions which are necessary to enable designers to develop circuits for applications in a wide range of operating environments. The results of a geometric analysis of the resistors are presented, and are used to permit accurate, simple electrical models to be made using analytical methods. The models are needed by process engineers to optimize resistor performance, and by design engineers as means of defining the correct component geometries for their circuits     

On the use of intensity optical pumping and coherent population trapping techniques in the implementation of atomic frequency standards

The paper summarizes the relative advantages and disadvantages of coherent population trapping (CPT) or intensity optical pumping (IOP) for the implementation of a passive atomic frequency standard using the isotope /sup 87/Rb. This paper outlines the basic principles common to both CPT and IOP when using laser optical pumping, and makes explicit their similarities and their differences. This paper describes experimental results obtained in the same cell on the characteristics of the CPT and IOP /sup 87/Rb-hyperfine-resonance line. The measurements showed that the signal contrast is larger in CPT than in IOP for the same resulting line width; the light shift is smaller in CPT than in IOP, and is easier to control; in principle, a passive frequency standard based on CPT has a smaller size than that based on IOP, due to the absence of a microwave cavity. Conclusions on overall expectations for the future of such frequency standards are drawn.     

Signal detection using third-order moments

The noise suppression capability of higher-order moments and spectra has made them attractive when the goal is to extract or reconstruct a signal that is contaminated by multivariate Gaussian noise or certain types of non-Gaussian noise. Two new detectors, one centralized and one distributed, which are based on the third-order moment of the data are proposed. The asymptotic performance of the centralized detector and the asymptotic distribution of the components of the distributed detector are analyzed. Further, the performance of these detectors is simulated and compared to that of the matched filter for three different types of interference: Gaussian noise, Gaussian noise corrupted by a sinusoid with random phase, and Arctic under-ice noise.     

Calculation of error probabilities for distance-invariant nonlinear error control codes

Expressions are given for the distance distribution of some nonlinear codes which enable error probabilities to be calculated using methods commonly associated with linear error control codes.<>     

Field dielectric measurements of frozen silt using VHF pulses

Radiowave propagation experiments utilizing short pulses in the VHF band were conducted in the permafrost tunnel at Fox, Alaska. The purpose was to measure dielectric properties of this naturally occurring, perennially frozen organic silt which is common to much of interior Alaska and for which ice content varies between about 54 and 79% by volume. Transmissions across a septum dividing two drifts gave relative dielectric permittivity values between 3.9 and 7.3. The low values resulted when transmission was predominantly through an ice wedge. Propagation along the septum gave values of 3.3 and 5.0 depending on antenna polarization. This propagation was influenced by the dry, surface silts, as was propagation along a ceiling section, which also gave an approximate value of 3.3. The data from attempted transmissions from the ground surface directly above the tunnel to the tunnel ceiling (approximately 12 m distance) are ambiguous, as signals that propagated indirectly along the transmitter cable through a nearby ventilation shaft may or may not have masked direct transmission through the permafrost. The results agree with previous laboratory investigations conducted at temperatures well below that of naturally occurring materials in interior Alaska suggesting that winter refrigeration of the tunnel by circulated outside air greatly affected the natural conditions at this site.     

The potential value of small responses and partial solutions

At the turn of the century, Taiwan's population was increasing slowly, then later grew during a period of high fertility after the end of World War II and the accordance of independence in 1946. This growth in fertility came together with increasing life expectancy and a general desire by couples to have families comprised of 5-6 children. Taiwan was therefore poised to experience a major population explosion. In this context, a family planning program was established in the country which has since evolved into one of the world's most successful such programs. By 1990, the preferred family size was 2-3 children and of couples which already had 2 children, 70% of those without any sons were nonetheless practicing contraception. While in 1965, no married women used contraception until they had some children, by 1990, 27% of married women without children used contraception. Increasing age at marriage has been an important factor in Taiwan's declining fertility, with the average age at marriage increasing from 20 years in the 1950s to approximately 27 in the 1970s. Few mothers, however, want only one child. The fertility trends observed in Taiwan have been made possible through the provision of contraception, which used to be universally free, but which is now provided free to only people of low income or the disabled. Oral contraception, condoms, and IUDs are used, although 30% of couples depend upon sterilization.