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Communication Technology, IEEE Transactions on

Issue 4 • Date August 1966

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Displaying Results 1 - 25 of 27
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Performance of a Multiple Address RADA System

    Page(s): 369 - 372
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    Potentialities and limitations are derived for a random access, discrete address (RADA) communication system in which addresses consist of time-frequency coded pulses and in which a higher order alphabet is realized by assigning many different addresses per person. The performance of such a multiple address RADA system is derived as a function of two parameters: the channel utilization and the size of the time-frequency matrix. The channel utilization is the ratio of the total information rate to the channel bandwidth. The size of the time-frequency matrix, in which addresses are formed, is a measure of the receiver complexity. If there is no limitation on matrix size, arbitrarily low probabilities of error can be obtained for any value of channel utilization below 70 percent by increasing the number of addresses per person. If both matrix size and channel utilization are fixed, a minimum error probability is achieved with an optimum number of addresses per person. The performance of a multiple address RADA system is shown to be generally superior to that of a single address ON-OFF RADA system. View full abstract»

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  • Further Analysis of an Integrated Switching and Multiplexing (ISAM) System

    Page(s): 373 - 381
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    This paper is an extension of earlier analysis work relating to a new method of achieving frequency division multiplexing, capable of being effectively integrated with time division switching. The band shifting inherent in frequency division multiplexing and demultiplexing is achieved by placing a sampling gate between a baseband and a sideband filter. When this technique is combined with time division switching, the transmission path also includes the cases of transmission via a switch between sideband filters, that may or may not cover the same sideband region, and between baseband filters. Resonant transfer is incorporated for all cases. Only the case of resonant transfer between baseband filters has been considered in the past. In general, the basic transmission path under analysis is the one between sideband filters, where the term sideband is used in the sense to include baseband. This is logical, since the baseband may be considered to be an upper sideband around zero frequency. Such a basic transmission path is rigorously analyzed on the basis of certain ideal assumptions. The purpose is to provide further insight into the fundamental operation of this new modulation-demodulatian scheme. View full abstract»

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  • A Statistical Analysis of Telephone Circuit Error Data

    Page(s): 382 - 389
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    Berger and Mandelbrot in 1963 proposed a particular renewal process as a model for the occurrence of errors in data transmitted over telephone circuits. Besides the assumed independence between the successive intervals between errors, they assume that the intervals have a Pareto distribution. Their graphical analyses of large amounts of data indicated departures from the model which Mandelbrot proposed in 1964 to account for in an extended model. Some simple formal statistical procedures are given for analyzing this sort of data, procedures that are not affected by the possibility that the population mean-interval-between-errors is infinite. The departures from independence of intervals noted by Berger and Mandelbrot are formally verified from the analysis of data from a single data transmission test. A separate analysis of another set of data is also made and the results are compared to see what features of the error patterns are general, and what features are particular to different transmission conditions. In both sets of data analyzed, the outstanding feature detected is the strong positive correlation between successive long intervals between errors. Evidence is also found which indicates that the upper tail of the marginal distribution of intervals between errors does not follow a hyperbolic law. View full abstract»

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  • Communication nets in random behavior

    Page(s): 389 - 399
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    Concepts of random neural nets, as treated in mathematical biophysics, are used to describe the random behavior of communication nets. Application of the steady-state as well as message spread threshold concepts to communication nets are considered. The steady state here implies a systematic and regular spread of the message while the spread threshold, referred to as the "ignition" threshold in neural nets, determines the required threshold minimum number of links ensuring, eventually, a steady-state activity, namely, a regular spread of the message throughout the net. The derived formulas offer useful computational tools in the treatment of strategic nondirectory nets in random behavior. Section II discusses the use of the spread of contagion theory and Section III deals with the random behavior of mobile communication nets, with directional and nondirectional antennas. View full abstract»

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  • Binary Error Probabilities Over Selectively Fading Channels Containing Specular Components

    Page(s): 400 - 406
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    This paper derives a general expression for error probabilities in binary transmission of signals over selectively fading diversity channels, containing specular and scatter type components. Post detection diversity combining is employed at the receiver, and a general form of detector that includes the usual coherent and incoherent detectors is assumed as a special case. Recent results of other authors are cited as special cases. View full abstract»

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  • Response of an AGC Amplifier to Two Narrow-Band Input Signals

    Page(s): 407 - 417
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    The response of an automatic gain control (AGC) amplifier to two narrow-band input signals is analyzed with respect to weak signal suppression and cross-product generation. A linear control characteristic is assumed. Results are obtained for a wide range of relative input-signal levels and frequency spacings. It is shown that the weak signal suppression and cross-product generation decrease, with increasing frequency separation, relative to the closed-loop AGC bandwidth. With the proper choice of AGC time constant and frequency spacing, it is possible to control the total power level of several signals without undesirable interaction among the signals. For certain asymptotic results, it is shown that the AGC performance coincides with that of a hard-limiter. View full abstract»

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  • Optimal Design of One-Way and Two-Way Coherent Communication Links

    Page(s): 418 - 431
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    This paper is concerned with the optimal design of one-way and two-way communication systems which are of greatest interest in space applications. A two-way communication system is defined to be one composed of two radio links or channels, viz., an up-link channel and a down-link channel. The down-link RF carrier is derived from the carrier tracking loop located in the uplink receiver. Transmission of information which does not make use of the carrier derived in the up-link receiver is referred to as oneway communications. In particular, a design technique is presented in the form of a universal set of design curves which enable the communications engineer to make a "best" choice of parameters when faced with a given set of design constraints. This means that, given a certain desired error probability, a total transmitter power limitation, data rate, and carrier tracking loop bandwidth, the modulation index, i.e., the square root of the ratio of the power in the carrier to the total transmitted power, may be chosen so as to minimize the probability of error. As an alternate technique, and one which is not as difficult to carry out, the design may be predicted on the basis of selecting that value of modulation index which maximizes the signal-to-noise ratio at the output of the data demodulator. Design curves are given which allow one to employ this alternate criterion. Further, these results should prove useful when attempting to check experimentally a design based upon the criterion of minimum error probability. View full abstract»

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  • Design and Analysis of a Linear Phase-Locked Loop of Wide Dynamic Range

    Page(s): 432 - 440
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    Consideration is given to a phase-locked loop configuration which provides a linear control characteristic over a range of 2π radians. Loop configurations employing pulse-amplitude-modulation (PAM) and pulse-duration-modulation (PDM) sawtooth phase comparators are outlined. The performance of the loop in a noise-free environment is determined for the case where the loop filter is of the perfect proportional-plus-integral control type. Expressions for the normalized pull-in time are obtained, and the results are compared with those available for the conventional loop employing a sinusoidal comparator. The limitations of this technique, as well as loop performance in a noisy environment, are also discussed View full abstract»

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  • Distortion of FM Signals Caused by Channel Phase Nonlinearity and Amplitude Fluctuation

    Page(s): 440 - 448
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    The distortion of FM (frequency-modulated) signals after being processed through time-invariant channels with nonlinear phase characteristic and/or fluctuating amplitude function is considered, starting from a Fourier spectral analysis of the signal. Expressions for calculating the distortion power or harmonic amplitudes, applicable to both single-tone and multitone message signals, are derived in terms of coefficients in the power series representation of channel phase characteristics. The quasi-stationary method is shown to be correct only in the leading term in each order of the distortion voltage. The missing terms can cause substantial errors in certain instances. Fluctuation in the channel amplitude function vs. frequency also causes change in the phase of the signal; the distortion generated is, however, one order of magnitude lower. Using a Butterworth-type bandpass filter as a particular example, the third and fifth harmonic amplitudes in the discriminator output are hand-calculated and plotted as a function of the modulation index. Results agree quite well with recent data from digital machine computations by Schenck and Kennedy. The spectral technique is also used to compute the channel bandwidth requirement, based on distortion considerations, and a family of curves is plotted from results of numerical computations on a digital computer. View full abstract»

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  • FM 120/5000 Radio Link System

    Page(s): 449 - 455
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    A radio communication system, primarily suited for military application, is described, general design objectives are outlined, and some features, such as rapid standby switching arrangement, are discussed in detail. View full abstract»

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  • Microwave Receiver Interference Characteristic Measurements

    Page(s): 455 - 469
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    Interference measurements on a 6-Gc/s microwave receiver at RF frequencies for 600- and 960-channel loading are described. The receiver used a 70-Mc/s IF amplifier with a 25Mc/s bandwidth. The mechanism for creating interference at RF frequencies is presented and is verified by many figures that relate the interfering signal level at several baseband frequencies to the magnitude and relative frequency of the interfering carrier. The measurement technique, which is fully described, used a swept backward wave oscillator (BWO) as the interfering carrier, and a recorder tracked the BWO frequency and provided a continuous plot of interfering signal level from the output of a noise-loading test set receiver for combinations of noise modulation on both carriers. Use of the data is described, and a generalized chart is given for a constant -78 dBmO interfering signal level, with and without preselection for variations of interfering carrier magnitude and frequency under different modulation conditions. View full abstract»

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  • Transient Response of Narrow-Band Networks to Narrow-Band Signals with Applications to Frequency Shift Keying

    Page(s): 470 - 477
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    A method is presented for simplifying the calculation of transient response of narrow-band networks to narrow-band signals. Laplace transforms are used, but employ only positive frequencies, simplified by approximations justified by the narrowband properties of the networks and signals. The method is applied in calculating the transient response of 1- and 2-pole band-pass filters to a step change of frequency of a signal whose amplitude is constant. Curves are included, showing the instantaneous amplitude, phase, and frequency of the filter outputs. View full abstract»

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  • Negative Resistance Devices Using A Multiple Number of Tunnel Diodes or Varactors

    Page(s): 478 - 483
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    The critical need for simple high-gain, low-noise microwave amplifiers and frequency converters, required for space communication and improved ground communication systems, appears to be met by the solid-state tunnel diode and varactor devices. The incorporation of these low-noise negative resistance devices results in significant improvement in the performance of communication systems where sensitivity is of importance. Past attention has been concentrated mainly on negative resistance devices using a single tunnel diode or varactor. This paper will present some results on devices using a multiple number of tunnel diodes or varactors. The behavior of devices using an arbitrary number of diodes in either a nonreciprocal or reciprocal environment is studied and compared with the single-diode configurations. For an amplifier usingntunnel diodes with parameters (- R_{1}, C_{1}), (-R_{2}, C_{2}), ...,(- R_{n}, C_{n}), the optimum gain-bandwidth limitation for a nonreciprocal configuration is given by(G_{T})_{n}leq exp [sum min{r=1} max {n} frac{2pi}{omega_{c}R_{r}C_{r}]where(G_{T})_{n}is the fiat transducer power gain and ωcis the bandwidth in rad/s for the amplifier usingntunnel diodes. This optimum gain-bandwidth limit can be realized by cascadingnstages of the optimum nonreciprocal single-diode amplifiers. For the reciprocal realization of the tunnel diode amplifiers, it can be shown that irrespective of the number of tunnel diodes employed, the optimum nonreciprocal matching can never yield more than 6 dB over the optimum reciprocal equalization. Thus, the fiat gain for the reciprocal case is given by(G_{T})_{n} leq frac{1}{4}[1+ exp (sum min{r=1} max{n} frac{pi}{omega_{c}R_{r}C_{r})]^{2}. Fornvaractors with parameters CorandC{1r}, r= 1,2, ...,n, the optimum nonreciprocal parametric amplifier - must satisfy the following limitation(G_{T})n leq cosh^{2} [frac{pi}{sqrt{omega_{so}w_{io}}{omega_{c}}(sum min{r=1} max{n} frac {C_{1r}}{C_{or}})]whereomega_{s0}andomega_{i0}denote the signal and idler band-center frequencies respectively. This result is a generalization of the gainbandwidth limitation for single-varactor parametric amplifiers published recently by the author [1]. Besides the results on gain-bandwidth limitations, the stability of the negative-resistance devices using an arbitrary number of tunnel diodes or varactors is also studied. Since both the tunnel diode and the varactor are two-terminal active elements, they must be capable of operating in a stable manner under at least one passive termination. Although a complete stability theory for tunnel diode and varactor devices is not as yet available, some useful sufficient conditions are derived in the paper for the stability of these negative resistance devices. Results presented in the paper on the important gain-bandwidth limitations and stability conditions are useful in the design and synthesis of stable, broadband, low noise tunnel diode and varactor parametric amplifiers incorporating a multiple number of diodes. Among the many possible applications for this theory, one can cite the phased-array systems and the pseudo-passive satellite techniques. In the latter application, a large number of tunnel diode amplifier units are integrated in an antenna structure to enhance the scattering cross-section of a moderate-size structure. View full abstract»

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  • Measurement of Polarization Statistics of Signals Received Over a Short Range HF Path

    Page(s): 484 - 494
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    A study was performed to measure variations in the polarization characteristics of an HF signal received over a short range ionospheric path. This paper describes a limited number of experiments using signals from Station WWV to determine the statistical nature of the polarization ellipse at the receiving site, Hathaway Hill, near Rochester, N. Y. The approach employed was to regard the elliptically polarized wave as the resultant of two linearly polarized waves of the same frequency and to measure the amplitude and phase of these two components by employing orthogonally oriented receiving dipoles and associated devices to provide continuous recordings of the variables. Three types of data were recorded during a one week field test period, and samples of each type were reduced and analyzed. The data compiled showed that the received signal exhibits Rayleigh fading characteristics with a mean fading rate of approximately 0.15 fades per second. The envelopes of the received components exhibit a high correlation in the morning hours, considerably less correlation in the afternoon, and a high correlation in the evening characterized by a substantial offset in time between the fading of the two components which is often periodic. The envelope of the cross correlation function indicates that the conditions causing the disturbance are changing slowly on a minute-to-minute basis, although complete polarization rotation appears to take about 5 to 10 seconds and is characterized by both phase and amplitude changes of the component waves. It appears that the milder perturbations of relative phase are confined within limits of approximatelypm90deg, and severe perturbations are characterized by a rapid monotonic change in the relative phase of the components of 2π. View full abstract»

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  • Laboratory Simulation of Multipath Propagation Effects on FM Systems

    Page(s): 495 - 498
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    A laboratory multipath simulator was developed to provide a controlled environment for the study of the nature of long delay multipath propagation interference effects on low-channel capacity FM systems, and for the evaluation of design changes on an existing system to improve its tolerance to a multipath environment. The associated laboratory program provided a valuable collection of information both in terms of multipath effects and in providing the field engineering force with a tool to confirm their findings. View full abstract»

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  • A Rake System for Tropospheric Scatter

    Page(s): 499 - 506
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    Experimental equipment has been developed which adapts the Rake concept to tropospheric scatter. This equipment enables experimental tests of multipath diversity effectiveness for communications. Its delay-resolution capabilities and circuit stability also allow effective use of the equipment for novel propagation research. The underlying concepts and equipment design are described, along with initial propagation test results. View full abstract»

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  • The Early Bird Project

    Page(s): 507 - 511
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    The Early Bird communications satellite is a commercial venture owned by a consortium of 52 countries. The system uses one spin stabilized synchronous satellite and five earth stations to provide a full-time microwave link between North America and Europe for 240 telephone circuits or for television. The 85-pound spacecraft was launched from Cape Kennedy on April 6, 1965, by NASA, using Thrust Augmented Delta Number 30. The launch sequence and subsequent maneuvers resulted in a circular synchronous orbit requiring no correction for seven months. The operational experience gained with this experimental/operational system has demonstrated satisfactory spacecraft performance characteristics and proven that synchronous communication satellites provide high quality links for telephone service. View full abstract»

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  • CATV Amplifiers: Figure of Merit and the Coefficient System

    Page(s): 512 - 520
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    A coefficient system has been devised which makes use of transmission objectives and amplifier performance to provide a new method of optimizing CATV system design. Maximum system length, in number of tandem amplifiers, is given for a reference amplifier. This number is called the system coefficient. Each other amplifier, either line or distribution, is assigned an amplifier coefficient which shows the number of reference amplifiers to which it is equivalent. For all amplifiers in tandem, the sum of the amplifier coefficients must be less than or equal to the system coefficient. This allows different kinds of amplifiers to be mixed in the same system and systems of different numbers of channels or bandwidth to be mixed to form a larger system. In addition, a line amplifier figure of merit can be derived which is independent of transmission requirements. View full abstract»

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  • The 1963 Survey of Impulse Noise on Bell System Carrier Facilities

    Page(s): 520 - 525
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    An outstanding characteristic of impulse noise on telecommunication channels is its high variability. A scientifically designed sampling plan was incorporated to conduct a survey of this type of noise on major Bell System carrier facilities. The results show mean impulse noise levels to range from 51 to 66 dBrn, and standard deviation of the nearly normal cumulative distribution functions of the levels to vary from 3.5 to 7.7 dB. Slopes of the peak noise amplitude distribution were found to range from 1.0 to 33.0 dB per decade with 90 percent of them falling in the range of 2.0 to 10.0 dB per decade. The variability of the noise parameters within single carrier groups or common routes was found, on the average, to be considerably smaller than exhibited by the entire system. View full abstract»

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  • Corrections [to "Error probabilities due to atmospheric noise and flat fading in HF ionospheric communications"]

    Page(s): 525
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    The author of the paper "Error Probabilities Due to Atmospheric Noise and Flat Fading in HF Ionospheric Communications," which appeared on pp. 266-279 of the September, 1965, issue of these Transactions, reports corrections to Equation (123). View full abstract»

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  • Corrections [to "On signal-to-noise ratios in communication systems"]

    Page(s): 525
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    The author of the correspondence item "On Signal-to-Noise Ratios in Communication Systems," which appeared on pp, 71-72 of the February, 1966, issue of these Transactions, reports corrections to equations (3) and (4). View full abstract»

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  • Some Properties of the Two-State First-Order Markov Chain

    Page(s): 526 - 529
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    This paper gives analytical derivations and graphical illustrations of the association factor, the stationary proportion of ONE'S, the symbol entropy, and the autocomparison function, as functions of the transition probabilities, for the 2-state first-order Markov chain. These properties of the chain have been found useful in the solution of certain practical problems in the field of information transmission. View full abstract»

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  • Plurality-Count Diversity Combining for Fading M-ary Transmissions

    Page(s): 529 - 532
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    The performance of a plurality-count diversity combiner for fadingM-ary transmissions is analyzed, and calculated error probabilities are presented graphically for alphabet sizes of 2, 8, and 32. The performance is shown to be within 3 dB of that of an optimum square-law combiner for moderate alphabet sizes when there is no restriction on the allowable number of diversity branches. It is shown that a worthwhile saving in transmitted power can be effected by using nonbinary alphabets with plurality-count combining for the transmission of binary data. The availability of extra information from the combiner for use with error-correction is discussed. View full abstract»

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  • An Experimental Comparison of Coding Vs. Frequency Diversity for HF Telegraphy Transmission

    Page(s): 532 - 533
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    This note reports a telegraphy test in which a Rate 1/2 error-correcting coding system was operated on two channels of an HF modem while an in-band diversity system transmitted the same information on two other channels. Error rates of coding and diversity operation are given, showing that coding was greatly superior to diversity when each used the same bandwidth. View full abstract»

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Aims & Scope

This Transactions ceased publication in 1971. The current retitled publication is  IEEE Transactions on Communications.

Full Aims & Scope