Generalized Design Equations Research Articles

Trade-off between preamplifier noise figure and decoupling in MRI detectors.

There is a limit to the maximum achievable preamplifier decoupling. In many cases, this level is not enough. To overcome this limit, the preamplifier noise figure can be compromised for further decoupling increase. This is useful in flexible MRI arrays where ensuring coil insensitivity to changes in other array elements is a challenge. This work establishes the relation between the preamplifier noise figure and preamplifier decoupling using closed-form equations. These equations allow the evaluation of preamplifier decoupling properties and benchmark different preamplifiers against each other. The method to design the corresponding decoupling networks is described. The derived generalized design equations, which are not limited to 50 Ω pre-matched preamplifiers, greatly improve design flexibility and enable use of new amplifiers in MRI detectors. Using the method, the decoupling properties of three preamplifiers are studied. For demonstration, the coil decoupling is further increased by 10.8dB using one of the preamplifiers. The noise figure is sacrificed by 0.5dB, which is predicted by equations and verified experimentally. Although examples are shown for 3T systems at 32.13 MHz and 127.7MHz, the approach and equations apply to any field strength and nucleus. Preamplifier decoupling can be improved beyond what is possible by traditional approaches. The derived design equations cover a wide range of cases, including inductive coils and self-resonant low-impedance and high-impedance coils.

Design of a Practical Metal-Made Cold Isostatic Pressing (CIP) Chamber Using Finite Element Analysis

The fast development of deep-ocean engineering equipment requires more deep-ocean pressure chambers (DOPCs) with a large inner diameter and ultra-high-pressure (UHP). Using the pre-stressed wire-wound (PSWW) concept, cold isostatic pressing (CIP) chambers have become a new concept of DOPCs, which can provide 100% performance of materials in theory. This paper aims to provide a comprehensive design process for a practical metal-made CIP chamber. First, the generalized design equations are derived by considering the fact that the cylinder and wire have different Young’s moduli and Poisson’s ratios. Second, to verify the theory and the reliability of the CIP chamber, the authors proposed a series of FEA models based on ANSYS Mechanical, including a two-dimensional (2D) model with the thermal strain method (TSM) and a three-dimensional (3D) model with the direct method (DM). The relative errors of the pre-stress coefficient range from 0.17% to 5%. Finally, the crack growth path is predicted by using ANSYS’s Separating Morphing and Adaptive Remeshing Technology (SMART) algorithm, and the fatigue life is evaluated by using the unified fatigue life prediction (UFLP) method developed by the authors’ group. This paper provides a more valuable basis to the design of DOPCs as well as to the similar pressure vessels than the previous work.

Outside Nominal Operation Analysis and Design Considerations of Inverse-Class-E Power Amplifier

In this paper, design and analysis using analytical expressions for the inverse class-E power amplifier (PA) operating at the outside nominal operation, i.e., class- $\text{E}_{\mathrm{n}}$ PA, is presented. This operation is defined as nonzero current switch (n-ZCS) and nonzero-derivative-current switch (n-ZDCS) conditions. The generalized design equations as a function of design specifications, load resistance, and a given dc-supply voltage are derived. Two degrees of the design freedom achieved thanks to n-ZCS and n-ZDCS that are utilized for the simultaneous satisfaction of design specifications, such as peak-switch-voltage and peak-switch-current along with a given load resistance. The output power capability is affected by n-ZCS and n-ZDCS conditions, which can be obtained in the desired value using the controlled adjustment of introduced deviation parameters. In order to prove the validity of the proposed design methodology, an inverse class-E PA operating in 2 GHz with output power of 23 dBm is implemented in 0.25- $\mu \text{m}$ AlGaAs–InGaAs pHEMT technology. There is a close agreement between the theoretical and simulation results and the measurements of the fabricated prototype PA, which proved the validity of the obtained design expressions.

Geometric Programming for Design Equation Development and Cost/Profit Optimization (with illustrative case study problems and solutions), Third Edition

Geometric Programming is used for cost minimization, profit maximization, obtaining cost ratios, and the development of generalized design equations for the primal variables. The early pioneers of geometric programming—Zener, Duffin, Peterson, Beightler, Wilde, and Phillips—played important roles in its development. Five new case studies have been added to the third edition. There are five major sections: (1) Introduction, History and Theoretical Fundamentals; (2) Cost Minimization Applications with Zero Degrees of Difficulty; (3) Profit Maximization Applications with Zero Degrees of Difficulty; (4) Applications with Positive Degrees of Difficulty; and (5) Summary, Future Directions, and Geometric Programming Theses & Dissertations Titles. The various solution techniques presented are the constrained derivative approach, condensation of terms approach, dimensional analysis approach, and transformed dual approach. A primary goal of this work is to have readers develop more case studies and new solution techniques to further the application of geometric programming.

Generalized design of continuous‐mode second harmonic tuned amplifiers

ABSTRACTThis article presents generalized design equations for achieving broadband second harmonic tuned power amplifiers (PAs) that are operated in class‐B, class‐AB, or class‐A bias conditions. The investigation is carried out by deriving the general intrinsic drain current and voltage waveforms for conduction angle, α, varying between 180 and 360°. New impedance solutions are then extracted using the generalized current and voltage equations. Shifted fundamental design space and expanded second harmonic impedance area are obtained when α is swept between 180 and 360°. A Gallium Nitride (GaN) fabricated PA is operated in class‐AB and delivers an output power greater than 40 dBm with minimum drain efficiency of 73% in the frequency band ranging from 500 to 950 MHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2787–2789, 2016

A new paradigm for star grain design and optimization

Purpose – The paper aims to extend the knowledge base for design and optimization of Star grain which is well known for its simplicity, reliability and efficiency. Star grain configuration is considered to be among the extensively used configurations for the past 60 years. The unexplored areas of treatment of ballistic constraints, non-neutral trace and freedom from use of generalized design equations and sensitivity analysis of optimum design point are treated in detail to bridge the gap. The foremost purpose is to expand the design domain by considering entire convex Star family under both neutral and non-neutral conditions. Design/methodology/approach – This research effort optimizes Star grain configuration for use in Solid Rocket Motors with ballistic objective function (effective total impulse) and parametric modelling of the entire convex Star grain family using solid modelling module. Internal ballistics calculations are performed using equilibrium pressure method. Optimization process consists of...

Design of Modified Countercurrent Liquid–Liquid Spray Column for Transfer of Surface Active Solutes in Presence of Interfacial Instability

Several design aspects of countercurrent spray column for transfer of surface-active solutes in the presence of interfacial instability have been analysed. On the basis of generalized design equations formulated for such a column, it has been shown that the height of the column for a given degree of extraction is significantly lower in the presence of interfacial instability with multiple feeding of organic phase from the bottom to several points up the column in comparison to a conventional design with the assumption of no instability. The example of a ternary system used is acetic acid–toluene–water.

Analysis and design of a high-efficiency multistage Doherty power amplifier for wireless communications

A comprehensive analysis of a multistage Doherty amplifier, which can be used to achieve higher efficiency at a lower output power level compared to the classical Doherty amplifier, is presented. Generalized design equations that explain the operation of a three-stage Doherty amplifier, which can be easily extended to an N-stage Doherty amplifier, are derived. In addition, the optimum device periphery, which minimizes AM-AM distortion for perfect Doherty amplifier operation, is analyzed. For the first time, a multistage Doherty power amplifier that meets wide-band code-division multiple-access (WCDMA) requirements is demonstrated. The designed power amplifier exhibits a power-added efficiency (PAE) of 42% at 6-dB output power backoff and 27% at 12-dB output power backoff. These PAEs are more than 2/spl times/ and 7/spl times/ better, respectively, than that of a single-stage linear power amplifier at the same output power backoff levels. The power amplifier is capable of delivering up to 33 dBm of output power, and has a maximum adjacent channel power leakage ratio of -35 and -47 dBc at 5- and 10-MHz offset, respectively. To the best of the authors' knowledge, these represent the best reported results of a Doherty amplifier for WCDMA application in the 1.95-GHz band to date.

Composite girder design by CAN/CSA S6-00: generalized design equations

This paper presents generalized design equations for concrete–steel composite girders. The equations evaluate the ultimate positive and negative flexural resistances of a composite section by addressing the issues of different design classes, varying locations of the neutral axis, and the possibility for either pseudoplastic or elastoplastic design. The equations may be readily implemented into design programs or spreadsheets.Key words: bridge, composite girders, design equations, elastic, elastoplastic, plastic, psuedoplastic.

An extended Doherty amplifier with high efficiency over a wide power range

An extension of the Doherty amplifier, which maintains high efficiency over a wide range of output power (>6 dB), is presented in this paper. This extended Doherty amplifier is demonstrated experimentally with InGaP/GaAs heterojunction bipolar transistors at 950 MHz. Power-added efficiency (PAE) of 46% is measured at P/sub 1dB/ of 27.5 dBm and 45% is measured at 9 dB backed off from P/sub 1dB/. Additionally, PAE of at least 39% is maintained for over an output power range of 12 dB backed off from P/sub 1dB/. This is an improvement over the classical Doherty amplifier, where high efficiency is typically obtained up to 5-6 dB backed off from P/sub 1dB/. Compared to a single transistor class-B amplifier with similar gain and P/sub 1dB/, the extended Doherty amplifier has PAE 2.6 /spl times/ higher at 10 dB back off and 3 /spl times/ higher at 20 dB back off from P/sub 1dB/. Under different bias and output matching conditions, the amplifier was also evaluated with CDMA signals. At the highest measured power of 25 dBm, the extended Doherty amplifier achieves a PAE of 45% with an adjacent channel power ratio of -42 dBc. Generalized design equations are also derived and the consequences of finite device output impedance on amplifier gain and linearity are explored.

Generalized design equations for backmixed liquid extraction columns with nonlinear equilibria

Two methods are described, in terms of the backflow model, for calculating explicitly the number of nonideal stages required in a backmixed multicompartment extraction column with nonlinear equilibria to achieve a given performance

Adjustable Mechanisms for Exact Path Generation

The generalized design equations for a path generating cam-link mechanism are developed. A cam-link provides a continually adjustable link that provides accuracy over a range of motion not available with coventional linkages. The design equations are used with an optimization scheme to satisfy a merit function based on cam pressure angle and drift angle. Examples are included that illustrate the capabilities of this synthesis technique.

Bias-Controlled Tunnel-Pair Logic Circuits

A three-terminal network consisting of two matched tunnel diodes and a fixed resistor is introduced as a basic element for performing peak threshold summation logic. The characteristic between two terminals resembles a tunnel diode curve where application of a signal or bias current to the third terminal causes reduction of the observed peak current. Decrease of this peak current below a fixed load line allows switching from the low- to the high-voltage state for logic-function circuit operation. Such bias-controlled tunnel pairs are shown to be unilateral to a considerable extent (30 db). This is advantageous in logic networks since it allows directional flow of information without the provision of multiphase power supplies or backward diodes, as needed in conventional tunnel diode logic circuits to eliminate back-switching. Circuits are described based on this principle, consisting entirely of tunnel junctions and resistors, for performing OR, MAJORITY, AND and NOR logic. Generalized design equations for circuits with a fan-in of M and a fan-out of N are derived. Test circuits based upon the generalized equations with a fan-in of 9 and a fan-out of 5 were found to operate over a temperature range from -70° to +60°C. A sample switching speed measurement for an OR gate using 1-ma tunnel diodes and a normal degree of drive showed a 7.5-nsec rise time which was triple that observed with a single tunnel diode under similar conditions.