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Communication Technology, IEEE Transactions on

Issue 2 • Date April 1970

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Displaying Results 1 - 14 of 14
  • [Front cover and table of contents]

    Publication Year: 1970 , Page(s): 0
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    Freely Available from IEEE
  • Field Experience with C1 EAX

    Publication Year: 1970 , Page(s): 85 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (746 KB)  

    The C1 EAX is an electronic switching system developed to meet the needs of class-5 central offices of up to 2400 lines and trunks. This system, the special field trial arrangements, and the experiences of the first year of operation are briefly described. View full abstract»

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  • Communications System Command and Control

    Publication Year: 1970 , Page(s): 90 - 96
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    Communications system command and control is essential to effective management of a dynamic communications system. An evolutionary concept is described, which has been proven in practice, of a method of controlling a dynamic communications system, of some of the equipments developed for this purpose, and of the major advantages of reporting and displaying system and equipment quality-control information on an automated near-real-time basis. View full abstract»

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  • Communications Efficiency of Certain Digital Modulation Systems

    Publication Year: 1970 , Page(s): 97 - 102
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (586 KB)  

    The efficiency as measured by data rate per unit bandwidth of certain digital modulation systems is compared. The systems considered are frequency modulation (FM), phase modulation (PM), and linear modulation. The achievable bits per cycle in digital PM and amplitude modulation (AM) at a given signal-to-noise ratio and error rate have been known for some time. In digital FM this quantity can be maximized, a fact apparently first realized by J. R. Pierce at Bell Telephone Laboratories. Rigorous optimizations were later carried out by Mazo, Rowe, and the author. In addition to the comparisons made with other systems, additional details related to the optimization problem in frequency-shift keying (FSK) are also furnished. Whereas previous treatments analyzed a frequency discrimination system, this paper treats the optimum detector. The results indicate very minor differences m efficiency attained by the two different models analyzed. Results are exhibited graphically, showing the relationships between the important system parameters. View full abstract»

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  • Transionospheric Propagation of FM Signals

    Publication Year: 1970 , Page(s): 102 - 109
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (814 KB)  

    Communication links to earth satellites are not usually affected adversely by propagating through the ionosphere. However, the nonlinear variation of the refractive index with frequency causes a dispersion which can result in significant signal distortion under certain circumstances. Such a case occurs, for example, when a wide-band frequency-modulated (FM) signal propagating at the lower carrier frequencies traverses a low-elevation path through a disturbed ionosphere. Expansions are now available for the spectrum of the output phase of an angle-modulated signal which has been passed through a generalized linear filter. The ionosphere is modeled as such a filter in this study and the spectrum of the demodulated signal is determined. From this, formulas are obtained for the output signal-to-distortion and signal-to-crosstalk ratios. The spectral results are presented graphically for FM with a uniform baseband, and two cases of current interest are examined numerically View full abstract»

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  • An FM Detector for Low S/N

    Publication Year: 1970 , Page(s): 110 - 118
    Cited by:  Papers (30)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (697 KB)  

    Conventional frequency-modulation (FM) detectors show a marked decrease in output S/N below an input S/N of 5 to 10 dB. This threshold effect is caused by "clicks" or phase slips of multiples of π. This effect is related to a normalization (clipping) which is very beneficial at high S/N . A detector is described which has no normalization and is superior to the ideal detector below zero to 10 dB input S/N . The noise at the output of the detector is additive for all input S/N ratios and in this sense is comparable to synchronous detection of AM. Plots of output noise spectrum and output S/N with and without sine-wave modulation are given. Another detector is also proposed that is asymptotic to the ideal detector at high S/N and the aforementioned detector at low S/N . Comparison is made with conventional detectors. The results indicate that this detector may be especially useful in the detection of frequency-shift keying and phase-shift keying in telemetry systems. View full abstract»

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  • On a Solution to the Second-Order Phase-Locked Loop

    Publication Year: 1970 , Page(s): 119 - 126
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (630 KB)  

    A solution of the stationary, mod-2π-reduced phaseerror probability density function for the second-order phase-lock loop is derived, based on a mean square fit to a certain unknown conditional expectation term. The resulting phase variance obtained from this density function yields an error that is negligible for \sigma _{\phi}^{2} \leq 1 and an error no greater than 0.06 rad2for signal-to-noise ratios (SNRs)≥ 2 dB by comparison with actual measurements, and it appears to be the most accurate to date. The usefulness of the result lies in the fact that an accurate estimate of the phase-error variance for arbitrary parameter values is easily obtained without the use of a computer. View full abstract»

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  • Intermodulation Effects in Limiter Amplifier Repeaters

    Publication Year: 1970 , Page(s): 127 - 135
    Cited by:  Papers (21)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (859 KB)  

    A method is presented for analyzing intermodulation (IM) spectra in limiting amplifiers using a statistical approach. Engineering approximations are derived for the case of a large number of input signals. The accuracy appears to be good down to seven signals. The approach permits analysis of arbitrary locations (in frequency) of the input signals. Possible ways of reducing IM interference in limiting satellite repeaters are discussed. The analysis is generally restricted to the ideal hard-limiting amplifier however, its applicability to other nonlinear characteristics is illustrated. Additional sources of degradation, such as amplitudemodulation-frequency-modulation (AM-FM) conversion and system phase nonlinearity, are not treated. View full abstract»

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  • Buffer Considerations for Data Compression of Nonstationary Video Data

    Publication Year: 1970 , Page(s): 136 - 141
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    Including a buffer storage into a telemetry data compression system has proven to be both a requirement and a nemesis. Some video compression simulation results which help define buffer requirements for transmitted bit-rate reductions of 2:1 and 3:1 are summarized. The zero-order predictor algorithm with a buffer-controlled variable aperture was found to provide both efficient buffer utilization and acceptable means of controlling buffer "underflow" and "overflow." The investigation was limited to worst-case nonstationary video data. View full abstract»

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  • Digital Transition Tracking Symbol Synchronizer for LOW SNR Coded Systems

    Publication Year: 1970 , Page(s): 141 - 147
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    In coded telemetry systems symbol synchronization must be performed at low symbol signal-to-noise ratios ( ST/N_{0} ) with negligible degradation from the perfect synchronization case. A digital transition tracking synchronizer which operates with less than 0.03-dB degradation at ST/N_{0} = -3 dB and at rates of 5.6 bit/s to 250 kbit/s is described. View full abstract»

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  • The PAR Meter: Characteristics of a New Voiceband Rating System

    Publication Year: 1970 , Page(s): 147 - 153
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    The peak-to-average ratio (PAR) meter provides a single number measure of the quality of circuits used for transmitting voiceband data signals. A PAR system consists of a generator and a receiver connected to opposite ends of a transmission network to be tested. The generator transmits a precise repetitive pulse through the system, and each pulse is dispersed by the distortions that it encounters. Then, the receiver responds to the pulse envelope peak and to the pulse envelope full-wave average and indicates the ratio on a zero suppressed scale. New equipment to obtain this measure has been designed to avoid ambiguities when used on systems with nonlinear distortion or phase intercept distortion. The PAR concept is reviewed, and the techniques used in this second-generation equipment to overcome these ambiguities and the affects of various distortions on the new meter's response are described. Also, PAR signal spectrum objectives and the measurement sensitivity to circuit parameters are listed. View full abstract»

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  • Compandorized Carrier-Frequency Program Transmission, Including Stereophony

    Publication Year: 1970 , Page(s): 154 - 158
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    Two 15-kHz channels positioned symmetrically in the 60-108-kHz-channel group are used for the transmission of two different programs or one stereophonic program. A new carrierfrequency compandor reduces noise by about 20 dB. The channel group is loaded with a mean power of 500 μW. View full abstract»

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  • Whistle Generation in Superheterodyne Receivers

    Publication Year: 1970 , Page(s): 158 - 159
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (219 KB)  

    A previous paper [3] dealt with seven receiver spurious response mechanisms. This paper shows that two of those mechanisms (intermediate-frequency harmonic and mixer p - q) can give responses at identical frequencies. A measurement method is described which allows the predominant mechanism to be identified, and it is shown that either response may predominate in practice. View full abstract»

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  • [Back cover]

    Publication Year: 1970 , Page(s): 0
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    Freely Available from IEEE

Aims & Scope

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

Full Aims & Scope