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Proceedings of the IEEE

Issue 3 • Date March 1969

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Displaying Results 1 - 25 of 34
  • [Front cover and table of contents]

    Page(s): c1
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    Freely Available from IEEE
  • Scanning the issue

    Page(s): 257
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    Freely Available from IEEE
  • The thermal structure of the ionosphere

    Page(s): 258 - 281
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    From a large number of rocket, satellite, and ground-based experiments since 1959 it is known that the electron and ion gases of the middle and upper ionosphere are substantially hotter than the neutral atmosphere. At low and midgeomagnetic latitudes the principal heating agent for the ionospheric plasma lies in the excess kinetic energy given to photoelectrons arising from the ionization of the atmospheric gases by solar ultraviolet radiation. Although the photoelectrons lose most of their kinetic energy in the excitation of atomic and molecular gases, a significant amount of energy is given to the ambient Maxwellian electron gas, increasing its temperature above that of the neutral gases. The ion gases, in contrast, appear to be heated almost entirely through the elastic collisions with ambient electrons so that the ion temperature generally lies between the electron and neutral temperatures. The calculation of theoretical temperature profiles has developed into a moderately sophisticated process with a fair degree of correspondence between predicted and observed values for undisturbed geophysical conditions. Current research emphasizes the global aspects of plasma temperatures and the connection between ionospheric and magnetospheric phenomena. However, many of the observed diurnal and seasonal variations in both electron and ion temperatures depend upon the couplings between the neutral and ionized atmospheres, and a complete understanding of all aspects of the ionospheric thermal balance is not possible at the present time. View full abstract»

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  • A low light level slow scan TV camera for satellite application

    Page(s): 281 - 291
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    A short description of the Owl satellite TV camera system and of several unique design features used with the secondary electron conduction (SEC) camera tube is presented. The dependence of the SNR on the scanning speed is analyzed, and the SNR is maximized for an amplifier employing a low noise field-effect transistor. The optimum scanning speed corresponds to an amplifier using a bandwidth of 8 kHz and a gate biasing resistor of a value in excess of 250 MΩ. To satisfy the requirements of optimum scan rate and low data telemetry bandwidth, an intermittent scanning procedure is employed in which the scanning beam touches the unscanned area of the target in a fraction of the scanning time only. This procedure combines the advantages of low noise level and high efficiency charge removal in a single scan. The single exposure scan feature reduces the efficiency of the TV system unless a small bias illumination is applied on the photosensitive surface to avoid the ineffiencies caused by the velocity distribution of the scanning beam. View full abstract»

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  • Calculation of the acoustic radiation field at the surface of a finite cylinder by the method of weighted residuals

    Page(s): 291 - 306
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    In the design of sonar systems it is desirable to compute the acoustic radiation field at the transducer surface, upon which all the significant radiation properties (radiation impedance, beam patterns, etc.) depend. Like other practical array geometries of interest, the finite cylinder does not belong to the class of separable coordinate surfaces of the Helmholtz equation, and consequently, the acoustic field for this geometry cannot be determined analytically. In this paper the surface field is computed numerically from the interior Helmholtz integral equation by the method of weighted residuals. Since the pressure fields over the three surfaces of the finite cylinder must coincide along the locii of intersection between the cylindrical surface and the end caps, the interior Helmholtz integral equation must he constrained to meet this requirement. The matrix representation of this equation which is not self-adjoint is solved by the method of least squares. This enables the constraints to be introduced via Lagrange multipliers. The procedure is used to calculate the surface pressure and radiation impedance of the finite cylinder for a range of axis ratios (diameter/length) and frequencies of interest in sonar applications. Calculations of the radiation resistance and the directivity index determined in this manner are shown to differ from those previously evaluated from the far-field solution. The weighted-residual methods considered are shown to have excellent convergence properties which make them more versatile than alternative numerical methods for solving the problem. View full abstract»

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  • Plasma physics and the interruption of an electric circuit

    Page(s): 307 - 323
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    This paper reviews the fundamentals of circuit interruption from both a scientific and an engineering viewpoint. The paper starts by discussing the interaction between a circuit interrupter and its associated power system. It then proceeds to describe the different methods of arc interruption. These first two parts form the background for the main purpose of this paper: to review the scientific understanding of arc interruption. Since the common ingredient in all circuit interrupters is the electric arc, the understanding of the process of circuit interruption is closely related to the scientific understanding of the behavior of arcs under both steady-state and transient conditions. Recent progress it this area is reviewed. Since arc interruption is a process during which a gas is changed from a high-temperature conducting state to a low-temperature insulating state, the knowledge of electrical breakdown of high-temperature gases is of fundamental importance, and this subject is discussed in some detail. References are provided for further study. View full abstract»

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  • The AN/FPS-85 radar system

    Page(s): 324 - 335
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    The AN/FPS-85 is a large operational UHF phased array radar designed and constructed for the U. S. Air Force by the Bendix Communications Division, Bendix Corporation. This paper gives a description of the radar's operation, some insight into the system design, pictures of actual hardware, a summary of system testing, and a project summary. View full abstract»

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  • On the computation of intermodulation products for a power series nonlinearity

    Page(s): 337 - 338
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    A recently derived formula for intermodulation amplitudes in a power series nonlinearity involved a multiple summation with many terms. An iterative scheme is presented for performing the summation which greatly reduces computing time, thereby making the formula practical even for cases where the input amplitudes are not small. View full abstract»

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  • A fast algorithm for computing the response of a linear system to a large number of inputs

    Page(s): 338 - 339
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    A method is presented which saves computation time when determining the response of an arbitrary linear time-invariant system, where several input-output responses are desired. The method is based on an assumption that the system input is band-limited. View full abstract»

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  • High CW power K-band Gunn oscillators

    Page(s): 339 - 340
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    Mechanically tunable K-band Gunn oscillators have been made which yield up to 120 mW of CW power at 24.8 GHz with an efficiency of 5.2 percent. View full abstract»

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  • Observations of voltage and current waveforms of the transferred electron oscillators

    Page(s): 340 - 342
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    The results of the observations of current waveforms of the resonant domain mode and the LSA mode are presented. The drift current which is very characteristic of the LSA oscillation is experimentally revealed by the subtraction of the displacement current from the total current, thereby confirming the oscillation of the LSA mode. View full abstract»

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  • Frequency conversion with gain through sideband locking of an IMPATT diode oscillation

    Page(s): 342 - 343
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    An up-converter with gain and stabilized frequency can be realized through the sideband locking of an IMPATT oscillator. An up-converter with a gain of 13.3 dB (microwave to microwave) and an output power of 13.3 dBm over the bandwidth 30 MHz is realized and operated at 10.18 GHz. View full abstract»

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  • Additional optical data processing techniques for surface roughness studies

    Page(s): 343 - 344
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    Three methods for determining the statistics of a surface's roughness are proposed. All three use some variation of the phase contrast method, and all appear to have advantages over a recently suggested method. View full abstract»

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  • A simplified optical correlator for radar-signal Processing

    Page(s): 344 - 346
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    Radar-signal processing is an interesting application of optical correlators. A simplified optical correlator is described and experimental results are presented. View full abstract»

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  • The effect of vignetting on the impulse response of coherent optical processors

    Page(s): 346 - 347
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    Passive linear electronic filtering systems are often assumed to be characterized by time-invariant impulse responses. It is shown that due to vignetting, their optical analog, the general coherent optical Fourier processor, is represented by a function analogous to a time-varying response. Hence, the usual convolution integral cannot be applied to it. Limits are also given on the maximum size of the input functions with respect to the aperture of the Fourier-transforming lenses. For "band-limited" Fourier filter functions, the impulse response becomes analogous to being time invariant for input sizes within specified bounds. These bounds represent a tradeoff between input size and bandwidth. View full abstract»

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  • Transient response evaluation from the state transition matrix

    Page(s): 347 - 349
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    A novel method for obtaining the transient response of a linear time-invariant system is presented. The main advantages of this method are that it eliminates the evaluation of the eigenvalues and also involves a minimal number of numerical steps. The method is illustrated by a specific example. View full abstract»

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  • Observation of the current and voltage waveforms of the Si IMPATT diode

    Page(s): 349 - 350
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    Current and voltage waveforms of the Si IMPATT diode were observed directly by means of the oscillating circuit using microstrip line. The results indicate that the conventional small-signal theory cannot be applied to the observed type of oscillation. The oscillation starts at the bias voltage just above the breakdon voltage of the diode; then along with its buildup, the bias voltage is lowered owing to the auto-bias effect, to reach a steady value considerably below the breakdown voltage. Large amplitude oscillation of high efficiency is expected over a wide frequency range. View full abstract»

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  • On narrow-band LC 70 MHz IF filters

    Page(s): 350 - 351
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    A practical method of designing narrow-band 70 MHz IF filters is described. The method is simple and straightforward and requires only a desk calculator. Experimental results of filters designed by this method agree well with their theoretical characteristics. View full abstract»

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  • Negative resistance in current-voltage curves of avalanche diodes

    Page(s): 351 - 354
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    The static current-voltage characteristics of silicon p+-n-n+diodes in avalanche have been measured and compared with theoretical predictions. The incremental negative resistance which is present causes the formation of high current density filaments. View full abstract»

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  • Microwave holograms using liquid crystal displays

    Page(s): 354 - 355
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    The use and limitations of liquid crystals for photographically recording microwave holograms are discussed. View full abstract»

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  • Green's function for the steady state of a periodically excited circuit

    Page(s): 355 - 356
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    The problem of finding the steady-state solution x(t) of the equation P^x(t) = Q^f(t) is studied, where f(t) is a periodical excitation, and P^and Q^are ordinary linear differential operators with constant coefficients For this purpose, a Green's function is constructed, which is the solution of the problem when the excitation f(t) consists of periodically applied pulses. This Green's function is then used in a convolution integral to find the steady-state solution for any periodical f(t). View full abstract»

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  • A temperature-stable RC transistor oscillator

    Page(s): 356 - 357
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    Generation of stable sinusoidal oscillations of fairly good waveform has been realized in a basic multivibrator circuit by optimizing load and coupling elements and introducing an amplitude defining mechanism with the use of emitter coupling. The resulting differential operation introduces an inherent tendency of self-compensation against changes of active circuit parameters, and the frequency remains practically independent of temperature change even though transistors are used. View full abstract»

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  • An analysis of thermal and space-charge spreading of electron beams from Guns of the pierce type

    Page(s): 357 - 358
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    An existing technique for analyzing the spreading of an electron beam in a drift space is extended to be valid for regions with an arbitrary variation of potential. Equations enabling the complete profile of the beam to be computed are presented. View full abstract»

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  • Space division multiplexing holography

    Page(s): 358 - 359
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    A technique is proposed for multiple information storage in a sampled hologram in long-wavelength holographies. An experiment on the proposed technique is conducted to construct a hologram using 15 kHz sound waves and to reconstruct images using laser light. View full abstract»

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  • Modified scheme for simulation of a delayor for polynomial inputs

    Page(s): 359 - 362
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    The steady-state response of any differential equation is a polynomial of the same degree as the input if the coefficients of the differential equation are so chosen that all the roots of the characteristic equation have nonzero negative real parts. If the order of the differential equation is the same as the degree of the input function, then under the steady-state condition the input and its derivatives can he obtained from the output and its derivatives which are readily available from the analog setup simulating the differential equation. From this a delayed or an advanced function can he generated by using Maclaurin's series expansion. The transient period of the scheme can be adjusted by a proper choice of the coefficients of the differential equation. View full abstract»

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North Carolina State University