Universal Charts Research Articles

Fundamental Limitations on the Output Power and the Third-Order Distortion of Balanced Mixers and Even Harmonic Mixers

A theoretical comparison of the fundamental limitations on the output power and the third-order distortion of balanced diode mixers and even harmonic mixers is described in this paper. In the authors’ previous work, formulas for the output power limitations of the mixers in a modulator operation were described. Using the described formulas, the output power and the third-order distortion of the mixers are calculated for a mixer operation and are represented as universal charts. Further, the closed-form formulas for the output power at a 1 dB gain compression and the intercept point of the third-order intermodulation products are presented. As mixers in a modulator operation, it is clarified that even harmonic mixers have a lower output power capability than balanced diode mixers. All the derived formulas were confirmed with experimental investigations at 100 MHz.

The role of nonlinear optical absorption in narrowband difference-frequency terahertz-wave generation

We present a general analysis of the influence of nonlinear optical absorption on terahertz generation via optical-difference frequency generation when reaching for the quantum conversion efficiency limit. By casting the equations governing the process in a suitably normalized form, including either two-photon- or three-photon absorption terms, we have been able to plot universal charts for phase-matched optical-to-terahertz conversion for different values of the nonlinear absorption coefficients. We apply our analysis to some experiments reported to date in order to understand to what extent multiphoton absorption could have played a role and also to predict the maximum achievable conversion efficiency at higher peak pump intensities.

Universal design charts for insulation of steel members in fire

Charts for insulation design of steel members in fire are usually provided by the manufacturers of the specified fire protection materials. These design charts may not be readily available, particularly for fire protection materials which may not have proprietary rights. This paper describes the development of a set of universal charts for the insulation design of steel members in fire for a wide range of fire protection materials of known physical and thermal properties. The main advantage of using these charts for insulation design is that they apply to all types of fire protection material without referring to the manufacturers’ design charts. In addition, high density fire protection materials, such as concrete, for steel members have also been included in these universal design charts.

SYNTHESIZING STATE-BASED OBJECT SYSTEMS FROM LSC SPECIFICATIONS

Live sequence charts (LSCs) have been defined recently as an extension of message sequence charts (MSCs; or their UML variant, sequence charts (MSCs; or their UML variant, sequence diagrams) for rich inter-object specification. One of the main additions is the notion of universal charts and hot, mandatory behavior, which, among other things, enables one to specify forbidden scenarios. LSCs are thus essentially as expressive as statecharts. This paper deals with synthesis, which is the problem of deciding, given an LSC specification, if there exists a satisfying object system and, if so, to synthesize one automatically. The synthesis problem is crucial in the development of complex systems, since sequence diagrams serve as the manifestation of use cases — whether used formally or informally — and if synthesizable they could lead directly to implementation. Synthesis is considerably harder for LSCs than for MSCs, and we tackle it by defining consistency, showing that an entire LSC specification is consistent iff it is satisfiable by a state-based object system, and them synthesizing a satisfying system as a collection of finite state machines or statecharts.

Optimization of a nonreciprocal phase shifter comprising a magneto-optic slab waveguide

The problem of a nonreciprocal phase shifter is solved analytically in the framework of first-order perturbation theory. The expression for the differential phase shift Δβ is valid for any set of material parameters. It is shown that an optimal Δβ is achieved for a film thickness smaller than that for maximal power confinement. Using scaled parameters and introducing a normalized nonreciprocal phase shift allow to obtain universal charts for the optimal film thickness and the corresponding nonreciprocal phase shift.

General aspects of beam threshold effects in LEED

We present in this paper some general aspects of beam threshold effects in LEED concerning their observation, their extension and their detection. The observation is possible on LEED intensities but also on crystal to ground current and total reflected current. We discuss the various types of profiles due to threshold effects for LEED intensities. From universal relations coming from emergence conditions of a new beam we draw universal charts for the “speed of emergence” versus E, θ or φ. These charts are used for a discussion of the range in I( E) or I(φ) profiles, where threshold effects may affect the LEED intensities. The same relations are used for a discussion of the detection of threshold effects. Assuming a Gaussian distribution (in energy and angles) for the incident beam, we derive a “total equivalent experimental resolution” and we discuss the consequence on intensity profiles and on the optimal conditions of detection.

Numerical field solution for an arbitrary asymmetrical graded-index planar waveguide

We present a numerical solution for the field amplitudes in an asymmetrical graded-index planar waveguide with an arbitrary index profile. For small index differences between the surface and bulk indexes and for large differences between the cover and surface indexes, the modes of the diffused waveguides can be described entirely in terms of normalized mode index, diffusion depth, effective modal width, and the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</tex> number. The results show a high degree of accuracy when checked against exact published results for the parabolic and exponential index profiles. Universal charts for the modal fields in terms of the normalized quantities are presented for profiles of practical interest, namely, Gaussian and complimentary error function index profiles. We show that the modal width, while somewhat sensitive to the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</tex> number, is surprisingly insensitive to the index profile. Tailoring of the index profile, therefore, does not seem important for the efficient fiber-waveguide endfire coupling. Error involved in the estimation of the phase shift at the cover-surface boundary as function of the asymmetry parameter is shown to be rather small for practical cases. Also, the discrepancy in the field distribution between an almost symmetrical and a highly asymmetrical waveguide at the cover-surface boundary is illustrated with a practical example.

Transmission Line Tower Grounding Performance in Non-Uniform Soil

Detailed computer analyses of a 765 kV typical transmission tower footing grounding performance during phase-to-ground fault condition are described and discussed. It is assumed the tower is erected on a two-layer earth structure. The tower resistance, worst touch and step potentials, are calculated for various soil conditions described by the top layer height and both layer resistivities. Universal charts are presented to help the engineer in predicting and designing transmission tower ground performance.

Scaling Rules for Thin-Film Optical Waveguides

An asymmetry measure is introduced to characterize thin-film optical waveguides that are asymmetric in refractive index. Together with the usual normalized frequency this allows the plotting of universal charts from which the guide cutoff, the effective guide index, and the effective guide thickness can be determined by the use of simple scaling rules. The minimum value of the effective guide thickness is found to be a simple function of wavelength and the film and substrate indices.

Two-twin-T cascade configuration

When two twin T's are connected in cascade in the feedback path of an amplifier, the response is different from the usual expectation. There are, of course, two selective peaks, but the frequencies of the two peaks are considerably different from the null frequencies of the twin T's. Universal charts have been given for the computation of these peak frequencies knowing the loop gain and the null frequencies, and vice versa.

Nonlinear distortion in common-emitter transistor amplifiers operated in the normal domain

Three nonlinear-distortion sources are analysed separately for polarity and magnitude of harmonics. If magnitudes are small, the resultant harmonic from these sources is the vector sum of its separated magnitudes. Universal charts are computed, to design amplifier circuits with simultaneous zero second and third harmonics. Experiments on an OC44 confirmed the theory, giving 2.5 mW with second to sixth harmonics better than -75 dB, power gain 40 dB, and no feedback or push-pull.

Characteristics Of Loaded Rectangular Waveguides

Electromagnetic fields of a rectangular waveguide with an arbitrarily loaded slab are theoretically analyzed. Eigenvalues for the transmission modes are presented in the form of universal eigenvalue charts. Electric field distributions in the loaded waveguide are obtained theoretically, and they are compared with the results of measurements. Power attenuation is also discussed, and attenuation charts that give the lowest limitation for the attenuation are shown. As an example of application the attenuation characteristic of waveguide resistance attenuators are investigated, and a new interpretation is derived for the phenomena where the curves of attenuation characteristic have sharp peak points.

Solution and Theoretical Evaluation of Steady-State Equations in Continuous Zone Refining

The classical theory of continuous zone refining is re-examined in light of alternate boundary conditions taking special care to account systematically for density changes due to melting. The new boundary conditions are applied to the zone-void and matter transport systems. Nondimensional parameters are introduced, leading to universal relations that have made it feasible to use an IBM 7090 computer to compute curves for a set of universal charts. These charts make it possible to explore for and choose rapidly optimum parameters for the design of continuous zone refiners for new materials and to evaluate existing proposals.