Practical Design Considerations Research Articles

A universal deflection unit generating a field of any order and azimuth

The magnetic field of line currents flowing axially along the surface of a circular cylinder and having a continuous distribution along the cylinder perimeter is given. The line currents are then limited to a finite number of equal sections, divided over the cylinder surface and forming an n-fold axially symmetrical configuration of current-carrying strips. The functional dependence of the generated field on the strengths of the various currents through these current carriers is derived. It is shown that any desired combination of homogeneous, quadrupole, hexapole, etc fields, all having their own azimuths, can be generated by just one unit of this configuration. Some practical design considerations and the results of an experimental test are given.

Analysis and design of temperature stabilized substrate integrated circuits

A generalized temperature-stabilized substrate integrated circuit system containing heat sources and temperature sensors which are distributed in an arbitrary way in two-dimensions over the surface of the chip is analyzed. A computer-aided technique for optimum placement of these components at the layout stage so as to achieve zero nominal temperature coefficient in the performance parameter of interest is described, and other practical design considerations, such as optimum choice of stabilized chip temperature, are considered. The application of this technique is illustrated with the design of a precision temperature stabilized voltage reference supply. Experimental results from this circuit are presented.

The Minimum Weight One-Dimensional Straight Cooling Fin

The Minimum Principle is used to obtain the minimum weight one-dimensional cooling fin without the length-of-arc assumption. This approach enlarges the class of optimum fin designs available for consideration. The heat-transfer coefficient and the, thermal conductivity can be temperature dependent. It is shown that the tip dimension vanishes for typical profiles. The results are specialized to make a comparison with results obtained with the length-of-arc assumption. With initial conditions obtained from the approximate method for kθ0/q0 = 10, the fin is 15 percent shorter than the classical parabolic profile and contains about 1.6 percent less material. The shorter fin length in this example and the flexibility in specifying the heat flux per unit fin base area for any fin are practical design considerations. The optimum fin is described by a nonlinear two-point boundary-value problem whose solution is obtained numerically. Computational guides are provided.

Experimental Investigations of Strongly Swept Turbine Cascades with low Speed Flow

Results are presented from an investigation into the blade to blade and meridional flow perturbations arising in high deflection turbine cascades subjected to large sweep angles. Experimental work has confirmed previous analytical estimates of the effect of sweep and indicated that certain common design procedures for the calculation of blade to blade flows are seriously in error. The significance of the results with reference to practical design considerations is discussed.

A cylindrical array for the TACAN system

A new cylindrical array has been developed for the TACAN ground antenna application. The technical requirements are unique since the circumferential radiation pattern is quasi-omnidirectional with multiple lobes and must be rotated at a precise rate. This is accomplished by electronically modulating the azimuth aperture distribution. Thus the antenna is a system including a specialized cylindrical array, a modulating RF feed network, and the associated electronic generator providing the required modulation and reference signals. Theoretical and practical design considerations are presented using a mathematical model of the antenna. This model describes the characteristic behavior and actual performance of the cylindrical array. The antenna's physical characteristics and design features are described, and measured array performance is presented in detail and compared to the system requirements. Operational performance data accumulated during actual flight test evaluation is presented briefly.

Practical design considerations for a variable center frequency, constant bandwidth, and constant peak-value active filter

Frequency active filters are designed by treating the operational amplifier as ideal. Consequently, the actual circuit's performance may depart considerably from what is expected. This is demonstrated in the design of an active bandpass circuit. However, it is shown that good agreement results between the predicted and actual performance if the operational amplifier's frequency dependence and output resistance are taken into account. Expressions are derived for the pole shift caused by the nonideal amplifier. Subject to given constraints, quantitative results are given that establish an upper bound on the frequency of operation of the bandpass circuit.

Pattern Synthesis of Linear Arrays Using Fourier Coefficient Matching

This paper presents a computer technique for synthesizing an array pattern for the practical problem in which only the magnitude of the far‐field pattern is specified. The general design problem is one in which both the currents and the spacings of the elements are allowed to be variables. The synthesis is based on a procedure which minimizes the norm of the difference between the Fourier coefficients of the desired and actual patterns. This criterion is very useful from practical design considerations since it allows one to determine a priori the highest order Fourier coefficient that can be approximated if the maximum array size is specified. Also, if no array size is specified, the procedure gives the array size necessary to obtain a given degree of approximation in the pattern.

Chapter 10 lighting of work places

The first part of this chapter deals with the principles of good lighting; these are common to both daylight and artificial light, and no attempt is made to distinguish between the two. In the second part which deals with practical design considerations, the essential features of each type of source are examined independently. The general requirements for good industrial lighting are summarised in the final section.

Analysis and design of multiple input flexible link mechanisms

A method for analyzing the force-displacement characteristics of multiple input flexible link mechanisms for both the static and dynamic cases is presented. The Finite Element Method for an elastic body used in the analysis is brieflly described by making the analogy with a single-degree of freedom discrete system. The link mechanism considered is a mechanical adder, providing incremental output motion for various combinations of displacement inputs, whose pivot points have been replaced by flexible joints. Good correlation with experimental results has been obtained for the static case. Also analyzed is the dynamic response of the system. An optimum design has been obtained by varying different parameters within the limits dictated by practical design considerations.

Design of electronic scanning radar systems (ESRS)

A format is presented for the design of Electronic Scanning Radar Systems (ESRS). Theoretical and practical design considerations unique to ESRS are emphasized. An introductory discussion of the role electronic scanning technology plays in fulfilling modern radar requirements is followed by a brief description of the generic types of electronic scan available to the radar designer. The system parameters affecting mission performance are listed. The corresponding radar functions that are particularly affected by the ESR selection are delineated, concluding with a discussion of the merits of the selection. Major decisions are single or multiple simultaneous beams and narrow, intermediate, or wide bandwidth performance capability. Automatic multitarget acquisition logic, computer controlled iterative tracking, equations, interpolative-null tracking, error budgets, and errors unique to ESRS are topics of discussion. The ESRS design procedure is illustrated with practical examples.

Metallic Seals for Deep Submergence Underwater Vehicles

Underwater vehicles require static and dynamic seals of axial or radial types to seal joints against high, external, hydrostatic pressures. Metallic knife-edge seals can do many of the sealing functions with superior performance in terms of pressure capability, low dynamic friction, controlled unit loading, low breakout force, self cleaning, and reusability. This paper discusses both the theoretical and practical design considerations of such seals and describes and evaluates experimental data generated to date by B. F. Goodrich.

The Improvement of Envelope Detector Performance Through the Use of a Nonlinear Transformation

In the design of many digital receiver systems, practical design considerations may dictate the use of envelope detectors and RC integrators. This paper analyzes the improvement which can be gained by the insertion of a nonlinear transformation between the envelope detector and the RC integrator. The characteristic curve of the optimum nonlinear transformation is determined and is found to yield an improvement of approximately 2.5 dB over the range of operating conditions analyzed. The form of the optimum transformation is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y=\frac{K_{0}}{K_{2} + I_{0}\frac{x}{\sigma\sqrt{2_{\gamma}} + K_{1}</tex> where K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> and K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> are arbitrary constants and K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> depends on the input signal-to-noise ratio γ and where σ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is the noise power at the input to the envelope detector. The performance of a suboptimum nonlinear transformation composed of a two-level quantizer (e.g., Schmitt circuit) is also analyzed and is found to yield a 1.5 dB improvement when adjusted to give the best performance. The best performance is achieved over a wide range of operating conditions when the threshold of the two-level quantizer is adjusted so that noise alone would cause a quantizer output of "one" 15 per cent of the time and "zero" 85 per cent of the time.

Response of Laminates with Dissipative Skins

Laminates made with plastic or reinforced plastic skins were sometimes found to have different damping characteristics than expected on the basis of conventional laminate theory. Investigation of the magnitude of damping of the plastic skins indicated that they had moderate internal damping. Laminates made with such skin materials can be considered as two-phase damping structures. The core contributes shear damping, and the skins add their own characteristic internal damping. Mathematical analyses of the effects of dissipative skins on the dynamic response of laminates are presented. Experimental verification is shown, and some practical design considerations are discussed.

A Photoelectric Grating Spectrometer

The astronomical advantages of a photoelectric grating spectrometer are outlined and the theoretical and practical design considerations are given for an instrument of this type recently constructed at the University of Manchester. It has a relative aperture of f /5 and a spectral resolving power of 20 to 25 thousand over the near ultra-violet and visible regions of the spectrum. Its angular resolution is of the order of the “seeing” disk when used with the 50-inch reflector at Asiago. Tests of the instrument are described, including its optical performance and its ability to compensate to a high degree for fluctuations in entrance slit iUuniination. A description is given of observations of the 3727 A O II radiation from the North America Nebula and luminescent radiation from the Moon. The accuracy with which this latter has been measured is considerably higher than that achieved by earlier observers and the implications of its existence are briefly discussed in the light of present day estimates of the lunar environment.

Use of Traveling Wave Helices in ESR and Double Resonance Spectrometers

Use of a traveling wave helix for concentrating microwave fields is discussed, with special attention given to application to electron spin resonance and Overhauser effects (double magnetic resonance). Some practical design considerations are treated. The influence of the standing wave pattern in the helix is treated in the Appendix.

A Waveguide Quadruplexer System

Practical design considerations are presented for a relatively simple four-channel wave guide branching system. The most important electrical characteristic of this system is an extremely low pass-band reflection coefficient (better than 1.5 per cent in 30-Mc band) which has only very small variations with the environmental conditions.

Novel Ultrasonic Hand Instrument

A new hand instrument, having numerous ultrasonic uses, and operated in the 25 kc/sec range, will be described and shown. This device is entirely portable and features a light weight hand-piece, which permits quick change of the transducer insert elements, without conventional mechanical attachments. The small electronic generator is of a new type and is semi-automatic insofar as frequency selection and control are concerned. The operating characteristics of this instrument will be described. Special emphasis will be given to the vibratory properties of the transducer which is utilized to produce simultaneously controlled longitudinal and flexural vibrations. This results in a variety of motions at the instrument's operating end. Practical design considerations led also to a new transmission line for connecting the magnetostrictive transducer to the operative output elements. An elementary coupling theory for the flexual and longitudinal vibrations will be presented in order to account for the elliptical mechanical motions achieved in practice.

A Novel Construction Concept for Linear Delay Lines

Previous attempts to design lumped parameter delay lines having linear phase characteristics required the use of compensating capacitors or coils. This paper presents a novel concept in construction techniques which results in a linear phase delay line without the necessity of resorting to any compensating components. A step-by-step design procedure for a low-loss linear delay line is used to illustrate this new construction technique. This novel line has a nominal characteristic impedance of 500 ohms, delay of l0 microseconds, low attenuation, and a cutoff frequency of 4 megacycles. This new work is based upon the theoretical treatment of the ideal low-pass filter by Golay;1the ideal parameter relationships have been reduced to practical design considerations involving unique geometric placements of ferrite cored components.

Two types of zero-velocity-error servomechanisms

This paper describes two types of zero-velocity-error servomechanisms which exhibit high dynamic accuracy with a minimum bandwidth. The first type is a special integral control system. The second type contains a simple lag circuit in the feedback path. These systems are analyzed and discussed from both theoretical and practical design considerations. A method to aid in the determination of required bandwidth is introduced. A classification of possible zero-velocity-error systems and a method of deriving zero-forced-error systems are also presented.

High-Frequency Compensation of RC Amplifiers

The high-frequency compensation of single- and multistage resistance-coupled amplifiers is discussed with special reference to the transient response. Optimum parameters are given for a number of typical cases. It is shown that, for the simplest type of high-frequency compensation with one coil in the anode lead, staggering of the time constants in a multistage amplifier reduces the rise time to less than 45 per cent of the uncompensated value, as against a reduction to between 55 and 60 per cent for the case of identical stages. Other practical design considerations are also discussed.