Browsing by Author "Loeb, H. W."
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Item Open Access An analogue method for the analysis of current carrying semiconductor systems(College of Aeronautics, 1963-09) Loeb, H. W.In an earlier Internal Technical Memorandum (1) and in subsequent work(2), it has been demonstrated that a particular kind of resistance network, in which non-linear elements are associated with each mesh point, can be made to represent an exact analogue to a non-degenerate semiconductor system in the equilibrium or quasi-equilibrium state. The term !exact' in this context implies that the difference equation which governs the potential distribution in the network becomes identical, for the limit of vanishing mesh interval, with the differential equation for the electrostatic potential within the semiconductor system, i.e. the Shockley-Poisson equation. From this type of analogue network information concerning the variation of maximum field intensity and of junction capacitance with applied bias voltages can be obtained for one, two and three dimensional configurations of p and n type regions of arbitrary geometry and impurity concentration profiles. One limitation to the applicability of the analogue technique arises from the restriction to quasi-equilibrium conditions. This restriction precludes the investigation of situations in which current flow contributions to the carrier concentration pattern become significant - for example, in the case of strongly forward biassed p-n junctions, and of p-i-n junctions and transistors operating at high injection levels. In the present paper, the problems involved in an extension of the basic analogue method to the treatment of non-equilibrium situations are examined, and means for their solution are discussed. A review of the methods previously described and an illustration of the nature of their limitations is given in Section 2. This is followed, in Sections 3 to 7, by a detailed treatment of the case of a current carrying semiconductor system in one dimension which leads to a theoretically possible realization in terms of resistancenetwork/ analogue computer techniques, which is, however, too complex to. be considered practical. Section 8 discusses means for the simplification of the proposed schemes and leads to the description of a relatively simple system in which a significant reduction in equipment complexity has been made possible by the adoption of an operating mode based upon an iterative process of successive approximations. The extension of the technique to three dimensions is outlined in Section 9.Item Open Access C.V.D. annual report: November 1965 research project RU27-1 :an analogue method for the determination of potential distributions in semiconductor systems(College of Aeronautics, 1965-11) Davis, J. A.; Loeb, H. W.A general method for the solution of the nonlinear Shockley-Poisson differential equation which governs the potential distribution in non-degenerate semiconductor systems is described which can be applied to the evaluation of depletion layer widths, carrier densities and capacitance bias relationships of p-n junction structures. The method is based upon the use of a particular type of resistance network analogue and results obtained for several one and two dimensional configurations are discussed.Item Open Access C.V.D. annual report: January, 1967 research project ru27-1 : analogue study of semiconductor device structures(College of Aeronautics, 1967-01) Andrew, R.; Loeb, H. W.The e::tension of the resistance network analogue method to the study of a M.O.S.T. structure is described. By means of an iterative technique, data regarding channel current, field distribution, surface charge and position of pinch-off point as function of gate and drain voltagen can be obtained which do not involve the usual 'gradual' channel approximation Results for a particular device geometry are presented. A discussion of a digital computer approach to the solution of semiconductor device current flow problems is included, together with preliminary results.Item Open Access Resistance network simulation of semiconductor systems(College of Aeronautics, 1964-09) Loeb, H. W.1. Introduction A basic problem in the design theory of semiconductor systems such as p-n junction devices relates to the determination of the spatial variation of electrostatic potential, 4, of electric field intensity, and of mobile carrier (hole, electron) concentrations, p and n ... [cont.].Item Open Access Theory and assessment of an improved power spectral density estimator(Cranfield University, 1990-06) Ali, Ali Abbas; Loeb, H. W.This thesis is concerned with the processing of time domain signals received by a single sensor. An example of such signals is the radar return, which is used in one way or another to estimate the power spectral density a frequency representation of the power of the signal in order that we can pick up and track the moving targets. since the POWER SPECTRAL DENSITY ESTIMATION is a fundamental tool in digital signal processing, the theory of the different approaches to PSDE is given in the Literature review chapter. The aim of this research is to develop a technique for the Power Spectral Density Estimation (PSDE) of multiple signals in white noise, which has high resolution capability and less frequency estimation errors. Hence, the various techniques mentioned above are tested for their detection, resolution capabilities and performance. Finally the different parameters affecting the resolution and detection capabilities of the Eigen Vector Decomposition Techniques (EVDT) for PSDE are studied in some depth.Item Open Access Time domain and frequency domain measurement techniques(College of Aeronautics, 1969-01) Loeb, H. W.The principles underlying two distinct approaches to the measurement of electrical network characteristics over a wide frequency range are outlined, together with brief descriptions of currently available test systems which cover the range 0.1 - 4GHZ. The two techniques are assessed in terms of their ultimate capabilities with regard to accuracy, speed of measurement and costs.Item Open Access Time domain and frequency domain measurements for transistor characterization(College of Aeronautics, 1966-05) Loeb, H. W.