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Communications Systems, IRE Transactions on

Issue 3 • Date September 1959

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Displaying Results 1 - 15 of 15
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Editorial

    Page(s): 145 - 146
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    Freely Available from IEEE
  • New Developments in FM Reception and Their Application to the Realization of a System of "Power-Division" Multiplexing

    Page(s): 147 - 161
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    Two techniques-feedforward across a limiter and dynamic trapping-are described to show how the message carried by the weaker of two cochannel FM signals can be extracted with negligible distortion even when its amplitude is much smaller than that of the stronger signal. The development of these techniques marks the end of the stronger-signal capture limitation of FM systems and ushers in more efficient spectrum utilization, as well as new applications for frequency modulation. View full abstract»

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  • Probability Distribution of Noise Due to Fading on Multisection FM Microwave Systems

    Page(s): 161 - 167
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    The probability distribution of expected baseband noise during fading at the end of a multisection microwave radio system is an important consideration in the engineering of a long system. This paper gives measurements of fading on a single path, and derives an estimate of the probability distribution of expected noise due to fading on a particular 68-section system of which the single path is a typical part. A comparison is shown with a measured cumulative distribution curve of noise at baseband subsequently obtained on the long system under operating conditions. A numerical method of combining distribution curves was used in this case and the so-called "breaking effect," due to deep fades, is included. This method is described in the Appendix. While this paper is directed specifically to a particular microwave system, the principles described can be applied equally well to others. View full abstract»

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  • Concerning Optimum Frequencies for Space Vehicle Communication

    Page(s): 167 - 173
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    Optimum frequencies for the varied needs of space vehicle communication can best be determined from the estimated system performance. Each of the contributing equipment and propagation factors over the range of the radio frequency spectrum affects the minimum tolerable signal-to-noise power ratio at the receiver. Over the range of the radio frequency spectrum, the behavior of the individual building blocks, as factors, will vary so as to exhibit a preponderance of either desirable or undesirable characteristics. Some of the newer technical developments that increase sensitivity to weak signals are evaluated for their potential increase in the distance of communication. Then the individual building blocks are married to each other in operating systems that determine the optimum portions of the frequency spectrum. The equipment factors are examined first, both as to their individual characteristics and their dependence on each other. Next, the propagation factors are examined for their effect over the range of the radio frequency spectrum in providing windows for communication through the earth's atmosphere, troposphere, and ionsphere to outer space. Some consideration is given to the effects of auroral displays, water vapor and gaseous absorption, Faraday rotation of polarization, and radio star scintillations. In addition, there is a discussion of noises arising from various causes. Measurements by radio astronomers demonstrate that equivalent noise temperature is a more useful measure of signal-to-noise ratio of receiver performance than the standard noise figure definition. View full abstract»

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  • Effects of Frequency Cutoff Characteristics on Spiking and Ringing of TV Signals

    Page(s): 173 - 179
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    The spiking and ringing of TV signals depend upon amplitude and delay characteristics associated with frequency cutoff of transmission. The effects of a variety of cutoff characteristics of both ideal and practical systems on rectangular and sine-squared pulses are illustrated by computed waveforms. The illustrations are arranged to show a) waveform of input pulse, b) amplitude and delay characteristics of transmission path, and c) waveform of output pulse. Included here is a discussion of inferences that can be drawn from certain output wavesforms on the reductions in transient response that are achieved by inband delay equalization and amplitude roll-off. View full abstract»

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  • A 2500-Baud Time-Sequential Transmission System for Voice-Frequency Wire Line Transmission

    Page(s): 180 - 184
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    The Sebit-25 is a full duplex terminal equipment designed to transmit digital data at rates up to 2500 baud. The equipment has been completely transistorized and thoroughly evaluated under environmental conditions. In operation, binary information at 2500 baud is converted to minimum bandwidth and used to amplitude modulate a 2500cycle carrier. The resulting signal is converted to vestigial sideband prior to transmission, to further compress the bandwidth. At the receiver terminal, amplitude and delay compensation are provided to correct for distortion introduced by the transmission line. Synchronous sampling of the recovered signal by a slaved time standard reproduces the original binary information even though line distortion may be severe. Excellent performance results were obtained from a series of laboratory tests conducted on the Sebit-25 to determine error probability vs noise, level changes, delay distortion, carrier frequency shift, and line filter variations. View full abstract»

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  • An Experimental Equipment to Reduce Teleprinter Errors in the Presence of Multipath

    Page(s): 185 - 188
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    Multipath propagation between radio terminals employing binary signalling elements produces a catastrophic rise in teleprinter error rate when the difference in path delay time becomes appreciable compared to the duration of a bit. A commonly used four-channel multiplex system has a bit length of 6.7 milliseconds and is thus seriously affected by differences in path delay greater than approximately 3 milliseconds. This paper describes a method of preventing the rise in errors when multipath propagation is present, by synchronously shifting the frequency of the transmitter and receiver following transmission of each bit. The receiver is thus responsive to the signalling element propagated by the shortest path and rejects the long path signals by filter selectivity. Spectrum occupancy and receiver bandwidth considerations which determine the magnitude and number of frequency changes are discussed, and a practical system is described. The general features of equipment used in testing this device are illustrated and discussed. The compatability of the anti-multipath equipment with existing equipment and the ability to reduce the error rate substantially, under conditions of ground-scatter multipath propagated by theFlayer, have been successfully demonstrated. View full abstract»

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  • Impulsing of Linear Networks in Integrated Data Systems

    Page(s): 189 - 194
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    Waveforms useful in data transmission may be obtained by impulsing suitable linear networks, and these same networks may be used, in certain cases, as receiving matched filters. A filter design for certain low-pass waveforms is described, together with a procedure for realizing band-pass analogs of these low-pass waveforms. The latter avoid the use of modulators. Practical results are described. View full abstract»

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  • Angular Diversity Reception at 2290 MC Over a 188-Mile Path

    Page(s): 195 - 201
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    Experiments were performed over the 188-mile Round Hill-Crawfords Hill path at 2290 mc to determine the feasibility of using angular diversity reception in a tropospheric scatter system. Using a 28-foot reflector, two beams were produced with two separate feed systems. The correlation of the signals received on one of the two beams with that received on the other was determined for various spacing of the beams, as well as for the azimuthal position of the antenna. These experiments show that angular diversity techniques can be effective depending on the proper choice of frequency, antenna size, and beam separation for paths in the neighborhood of 200 miles in length. A substantial "diversity gain" can be achieved even though partial correlation exists. These results also appear to be in good agreement with theoretical predictions for equal means and for the short periods of time applicable to obtaining reliable voice and high speed teletype communications. View full abstract»

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  • Real-Time Data Transmission System

    Page(s): 201 - 205
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    A real-time data transmission system was designed for and installed at the Atlantic Missile Range. This system is used to transmit the digital range, azimuth, and elevation coordinates from remotely located AN/FPS-16 radars into the Range Safety IBM 704 Computer at Cape Canaveral, Fla. The radar data is transmitted at a 10PPS rate and is used in the computation of a predicted impact point ten times a second within the computer. The predicted impact point is displayed on vertical plotting boards or use by the Range Safety Officer. View full abstract»

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  • Tropospheric Scatter Path Loss Tests--Florida Bahamas

    Page(s): 205 - 208
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    Telephone service between the United States and the Bahama Islands is now provided by means of high-frequency radio systems working in the 2-7 mc range. To handle properly the large volume of traffic during the peak winter season requires that more than the present nine circuits be provided. The lack of available frequencies in the 2-7 mc range, together with the comparatively poorer grade of facility obtained from these radio systems, makes it desirable to investigate other methods of providing telephone facilities. The fact that the present Miami-Havana tropospheric scatter system is performing so well, and that the distance from Miami to Nassau is the same as that to the Cuban terminal, made this type of system very attractive. At the time the Cuban system was being developed, klystron tubes capable of high outputs above 1000 mc were not available. For this reason, the Cuban system was designed to operate in the 700-900 mc range. Since that time tubes capable of high output levels at frequencies above 2000 mc have been developed, and it was considered desirable to operate at these higher frequencies rather than in the lower part of the UHF spectrum. Path loss tests were made over a nineweek period on the Florida-Nassau path using a frequency of 1970 mc. These tests are discussed and some comparisons are drawn between them and the path loss tests made to Cuba at 800 mc two years earlier. The Nassau tests indicated that a satisfactory 60-channel radio system could be provided through use of 10-kw transmitters and 30-foot parabolic antennas. View full abstract»

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  • Applicability of Multipath Protection to Meteor Burst Communications

    Page(s): 209 - 210
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    This paper investigates past methods of improving the duty cycle of meteor scatter communications links in the presence of multipath distortion and suggests using a technique, for further improvement, which has proved useful at HF frequencies. It notes also, that use of this technique in conjunction with improved endof-message error detection techniques should yield an improved duty cycle for meteor burst communications. View full abstract»

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  • A Formalized Procedure for the Prediction and Analysis of Multichannel Tropospheric Scatter Circuits

    Page(s): 211 - 221
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    In order to evaluate the potentialities of the scatter link and to minimize the financial risk involved in its implementation, examination of many combinations of path, sites, and system configurations is desirable. To assist this process, and to minimize the financial risks involved in uncertainties, a formal analytical procedure for the study of these circuits is desirable. The essential structure for such a procedure is outlined. A step-by-step process is involved, commencing with determination of an objective weighting factor for site evaluation. Data are presented for resolution of further steps dealing with median path loss, design accuracy, traffic loading, instantaneous fading, SNR, error rates, bandwidth and power. A performance index for path evaluation is used so that an optimum path-site combination may be selected. An index for comparison of various paths carrying different traffic loads with different reliabilities is suggested. Equations for the use of this data in specific design situations are also given. View full abstract»

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  • Contributors and back cover

    Page(s): 0
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    Freely Available from IEEE

Aims & Scope

This Transactions ceased publication in 1962. The current retitled publication is  IEEE Transactions on Communications.

Full Aims & Scope