• STANDARDS FOR GOVERNMENT USE OF THE SPECTRUM

      Hull, Joseph A.; IRAC Technical Subcommittee (International Foundation for Telemetering, 1973-10)
    • GSFC STANDARDS PROGRAM

      Poland, William B., JR.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
    • THE APPLICATIONS OF CODEM CONCEPTS FOR COMMUNICATIONS OVER THE AERONAUTICAL CHANNEL

      Chase, David; CNR, Inc. (International Foundation for Telemetering, 1973-10)
      The aeronautical channel characterized by multipath interference due to scattering and reflections off the surface of the earth represents a difficult channel for obtaining reliable data transmission. It is shown that interfering paths can be of sufficient strength and have Doppler spreads such that conventional forms of modulation are severely limited. In order to obtain error probabilities below 10^(-5) over a wide range of channel conditions, a robust signaling approach which is relatively insensitive to short term channel conditions is necessary. It is shown that these robust properties can be obtained by Codem concepts which jointly optimize the modem and coding design.
    • A DISCRETE ADDRESS BEACON SYSTEM

      Israel, David R.; Federal Aviation Administration (International Foundation for Telemetering, 1973-10)
      The two most basic requirements for air traffic control are surveillance and communications. The surveillance system in use today is the Air Traffic Control Radar Beacon System. It is based on World War II technology and is experiencing severe difficulties as the number of aircraft carrying transponders increases. This paper outlines the present FAA program to develop a new surveillance system which will eliminate the problems, will be compatible with the existing system and will also provide a digital data-link for collision avoidance and air traffic control purposes.
    • A SYNCHRONIZED DISCRETE ADDRESS BEACON SYSTEM

      Blake, Neal A.; Federal Aviation Administration (International Foundation for Telemetering, 1973-10)
      The Federal Aviation Administration is developing a Discrete Address Beacon System as a new air traffic control surveillance system. It will solve most of the problems of the present beacon system and will also provide an integral digital data-link for ground to air messages. This paper describes a particular implementation of the DABS concept which also provides air-to-air collision avoidance service and navigation service.
    • ASTRODRIVE - A NEW POWER-CONSERVING TAPE DRIVE

      Karsh, Irving; Bell & Howell (International Foundation for Telemetering, 1973-10)
      Astrodrive® is a regenerative magnetic tape drive providing tape speeds from 15/16 to 960 in./sec. The unit features mechanical simplicity and low power consumption, in a unique peripheral drive mechanism, suitable for cartridge-load, or conventional reel-to-reel transport arrangements. Both single and dual motor configurations of the basic mechanism are discussed, along with the inherent capabilities and limitations of each.
    • PLANETARY PROGRAM DATA SYSTEMS STANDARDS

      Glahn, Earl W.; Planatary Programs Data Systems Working Group (International Foundation for Telemetering, 1973-10)
    • TELEMETERING VIA LEAKY WAVEGUIDES

      Hu, A. S.; New Mexico State University (International Foundation for Telemetering, 1973-10)
      Telemetering through leaky waveguides is a combination of cable transmission and atmospheric transmission. This system carries radio signals in a confined space tube thus making signal transmission through tunnels, mines, and buildings possible. This paper discusses the history of development, the types of leaky waveguide, the transmission characteristics, and the performance evaluation methods.
    • THE INFLUENCE OF CARRIER FREQUENCY ON SNR FOR FM SYSTEMS

      Monson J. E.; Harvey Mudd College (International Foundation for Telemetering, 1973-10)
      The influence of carrier frequency on broadband signal-to-noise ratio is derived for a frequency modulated tape recording system. Optimum signal-to-noise performance occurs at the value of carrier frequency where the carrier-to-noise ratio is falling at 6 dB/octave. Signal-to-noise ratio is relatively insensitive to changes in carrier frequency about the optimum value.
    • SPECTRUM PROCESSING RECEIVERS FOR TELEMETRY APPLICATIONS

      Van Cleave, J. R.; American Electriconic Laboratories, Inc. (International Foundation for Telemetering, 1973-10)
      When the i-f filter of a telemetry receiver is replaced by a digital processor utilizing an intermediate orthogonal transformation into either the frequency domain using Fast Fourier Transform (FFT) or sequency domain using Fast Walsh Transform (FWT), then much improvement in performance may be expected. This paper discusses both application and results of FFT and FWT processing to: 1) a signal acquisition receiver providing extremely enhanced phase lock loop (PLL) acquisition speed; 2) an adaptive i-f bandwidth receiver providing a large i-f signal to noise ratio (SNR) improvement and also immunity to undesired EMI and/or jamming signals; and, 3) a signal evaluation receiver for measurement of SNR in the range of -30 dB and up. Spectrum processor design considerations and tradeoffs are presented.
    • A SHORT RANGE 15 MEGABIT/S LED COMMUNICATOR

      Dworkin, L. U.; Coryell, L.; USAECOM (International Foundation for Telemetering, 1973-10)
      The design, development, and testing of a short range (distances up to 100 ft) data communications equipment that utilizes a GaAs light emitting diode (LED) source is discussed. Data rates of 15 Mb/s are accommodated by a transmission terminal which consists of a line of sight (LOS) atmospheric portion and a fiber optic link. The system has an all weather capability, is relatively inexpensive and is intended for tactical military applications. This is the first attempt at developing a wideband optical communicator that has a similtaneous LOS and cable capability often needed in a tactical military environment.
    • A PCM DATA SEQUENCE CONTROLLER

      Sandia Laboratories; Johnson, Charles S. (International Foundation for Telemetering, 1973-10)
      The PCM Data Sequence Controller described in this paper is used to interface a memory-controlled PCM encoder with a plated wire memory to form a unique digital data compression and storage system. The memory-controlled PCM encoder is used to select formats and convert input analog data channels into a PCM bit stream which is both transmitted and stored in a plated wire memory. The encoder is also used to retrieve information from the plated wire memory and retransmit it. The system provides both temporary and permanent data storage for the telemetering of data in a severe environment.
    • Optran® AN INFRARED LED TRANSCEIVER FOR DATA COMMUNICATIONS

      Meyer, Andrew W.; Harting, Stephen W.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
      The following discussion reviews operating experience with a non-coherent infrared (IR) optical data link at several installations in the United States. Optran is a commercial digital data link, manufactured by Computer Transmission Corporation, for computer-to-computer or computer-to-terminal data transfer applications. It uses a nonlasing gallium arsenide diode as the transmitter and a silicon diode as the receiver. Simple optics collimate the transmitter output and focus the captured receive energy on the receiver diode. A digital interface unit at each terminal end presents a standard interface to business equipment and encodes/decodes data from the optical head.
    • DATA RELIABILITY

      Powers, S.G.; Radiation (International Foundation for Telemetering, 1973-10)
      In this paper the problem of achieving reliable digital information transfer in the presence of data errors is addressed. The approach taken is to reject data which is suspected of being in error under the philosophy that it is better to miss data than to receive it incorrectly. To this end, error detection mechanisms are considered and their performance compared for a specific application. The mechanisms are thresholding, error detection coding, waveform error detection and feedback. It is shown that error detection coding is the most effective, followed by feedback, thresholding, then waveform error detection. The results are summarized in Tables I and II. These tables give the undetected word error rate and missed word rates for the techniques considered. The application which originally inspired this work is the use of time-division multiplexing to transfer mission-critical data on the B-1 aircraft.
    • NEW MAJORITY-LOGIC DECODABLE CODES

      Chen, C.L. (International Foundation for Telemetering, 1973-10)
      A method of the construction of majority-logic decodable codes is presented. Many of the codes constructed are more efficient than any other comparable majority-logic decodable codes previously known.
    • MEASURING TERRESTRIAL RADIO FREQUENCY INTERFERENCE AT ORBIT ALTITUDES

      Bayol, Martin E.; Locke, Paul A.; National Scientific Laboratories, Inc. (International Foundation for Telemetering, 1973-10)
      Satellite systems, by virtue of their large terrestrial fields of view, may be exposed to a great many man-made radio signals the aggregate effects of which can be deleterious to satellite receivers. An experiment has been designed to measure and characterize such man-made interference at orbital altitudes. The experiment, as designed, requires dedicated hardware on a spacecraft of specified orbit and will measure (within the frequency range of 400 MHz to 12.4 GHz) peak levels of interference in cells dimensioned in space, time, and frequency. The experiment will provide data indicative of some of the statistical characteristics of interference levels at satellite orbital altitudes and will provide designers of satellite communications links with new facilities for the prediction and prevention of interference problems, and should provide a considerable data base for use in long range planning of spectrum utilization.
    • A SPACEBORNE RECEIVER FOR MEASURING ELECTROMAGNETIC FIELD INTENSITY

      Reich, B.W.; Van Dusen, M. R.; Habib, E. J.; National Oceanographic and Atmospheric Administration; Airborne Instrument Laboratory; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
      At the present time, considerable interference with communications to and from spacecraft has been experienced. Consequently, the need for determining the extent of this interference was indicated. NASA contracted AIL to design and build a very accurately controlled receiver to monitor the electromagnetic radiations in both existing and projected space communication bands. Based on analysis of the existing and projected space communication bands, 108 to 174 MHz, 240 to 478 MHz, and 1535 to 1665 MHz were covered. The receiver achieves accurate control via a digitally tuned synthesizer and a wide range of digital control including frequency band coverage and gain control selection. Digital memory was provided to store 16 separate digital command instructions which can be programmed via a command data link. The receiver provides for transmission to the ground of both a predetection signal and signals in digital format, which in turn, were provided by sampling and analog-to-digital conversions.
    • A VIDEO BANDWIDTH HE-NE LASER COMMUNICATION SYSTEM

      Pao, Yoh-Han; Freeman, J.P.; Allen, J.W.; Claspy, P.C.; Laser Communications Inc.; Case Institute of Technology (International Foundation for Telemetering, 1973-10)
      A He-Ne laser communication system with video bandwidth capability is described. The system is suitable for the transmission of video signals generally compatible with U.S. commercial practice, and the transmission of digital data at rates of approximately 10 to 1000 Kb/s, over ranges extending from a few hundred feet to about 10 miles. Relative to cable systems and microwave links, this laser system has the advantages of immunity from electromagnetic noise and from microwave interference, ease of installation, comparative freedom from regulation, mobile operation and lower costs. Possible occasional outages due to inclement weather constitute the principal drawback. This system is different from two other available types of optical links. The light emitting diode (LED) links are limited to short ranges and the laser injection diode (LID) links have low duty cycles and are not designed for video capability. The performance characteristics and operating data of a specific system, the LCI-203 system of LASER COMMUNICATIONS, INC. , are described in detail. Operating ranges and corresponding reliability figures are estimated for various geographical locations. Operating experiences in health care delivery and security surveillance applications are described.
    • A REAL-TIME HADAMARD TRANSFORM SYSTEM FOR SPECIAL AND TEMPORAL REDUNDANCY REDUCTION IN TELEVISION

      Noble, S. C.; Knauer, S. C.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
      A digital Hadamard transform system has been developed for the real-time compression of standard NTSC television signals. The system digitizes the video signals and subdivides four successive frames of data into suppictures of sixty-four picture elements. The subpictures are cubes four elements on a side, in horizontal, vertical and temporal directions. Subpictures are transformed and processed to reduce special and temporal redundancy. Implementation and performance results of the system will be described and discussed.
    • MILITARY COMMUNICATION SATELLITES

      Wall, Virgil W.; The Aerospace Corporation (International Foundation for Telemetering, 1973-10)