• PERFORMANCE OF A 350-Mb/s ADAPTIVE EQUALIZER

      Ryan, Carl R.; Stilwell, James H.; Motorola Inc. (International Foundation for Telemetering, 1973-10)
      This paper applies baseband adaptive equalization techniques to rf multipath and transmitter/receiver distortions. Included are test results comparing 350-Mb/s adaptive equalized and unequalized receivers. These comparisons are made with distortion typically encountered in a high data-rate line-of-sight microwave system such as demodulator quadrature errors, demodulator phase offset errors, and moderate rf multipath distortion. The design and construction techniques are also illustrated.
    • SATELLITE-AIRCRAFT DIGITAL TRANSMISSION EXPERIMENT RESULTS AT L-BAND

      Wilson, Stephen G.; Boeing Commercial Airplane Company (International Foundation for Telemetering, 1973-10)
      Results of an experiment involving the synchronous satellite relay of digital information at L-band between a ground station and a jet aircraft are described. Specific tests studied the performance of PSK signalling in conjunction with three distinct detection strategies for both the classical additive noise channels and the composite multipath channel (direct signal plus multipath). Tests were conducted at various signalto-noise ratios and direct signal-to-multipath ratios. Reasonable agreements with available non-fading and Rician fading channel theory is shown. Implications for the operational aeronautical satellite case are discussed.
    • ADAPTIVE ANTENNA ARRAY

      Smith, James M.; Sielman, Peter F.; AIL (International Foundation for Telemetering, 1973-10)
      A key problem in establishing and maintaining high quality communication repeater links among users, where the vehicle for retransmission is a synchronous orbit communications satellite, is that of enhancing the limited effective radiated power (ERP) capabilities of the smaller user against the not always so limited ERP capabilities of co-users or other sources of rf interference. The adaptive array which can supply narrow high gain custom shaped individualized beams weighted to reflect the ratio of user power to thermal noise and at the same time minimize the capacity reducing effects of intentional or unintentional rf interference emitters appears to be the most effective means of improving overall performance at least system cost.
    • A 10.6 μm TERRESTRIAL COMMUNICATION LINK*

      Goodwin, Francis E.; Nussmeier, Thomas A.; Zavin, Jack E.; Hughes Research Laboratories; U. S. Army Electronics Command (International Foundation for Telemetering, 1973-10)
      This paper reports the development of an experimental type 10.6 μm laser communication system, consisting of a transmitter terminal and a receiver terminal, designed to operate one wav over a nominal five-mile path. The system provides a 5 MB/s digital data channel using a frequency shift keying format and optical heterodyne detection with a mercury cadmium telluride detector operating at a temperature of 77°K. The system is the first CO2 laser heterodyne communication system which is capable of hands-off, uninterrupted operation in a nonlaboratory environment. The achievement of single frequency operation of a laser transmitter and local oscillator in a field system is the result of more than seven years of research and development. Laser frequency purity, stability and control, all questions of primary concern previously, have been proven satisfactory with the development of this system. This paper reports the operation of the system during environmental tests, over a 4.1-mile test range, a 19.5-mile test range at the Hughes facility, and over a three mile test range at Ft. Monmouth, N.J. over a period of several months. During a period of 1320 hours of continuous operation, the system was inoperable for 65 hours due to weather conditions, demonstrating a reliability of 95%.
    • RECONSTRUCTION OF DISTORTED SAMPLES IN DIGITAL TELEMETRY

      Berezin, V. I.; Sviridenko, V. A.; Trofimov, A. M.; Shtarkov, Yu. M. (International Foundation for Telemetering, 1973-10)
      The problem of processing of an analog-digital message, that is transmitted via the noise channel is digital form, is considered. A simple algorithm of correction of distorted samples is proposed with the use of one symbol for even parity checking and linear interpolation. The expression for a resulting mean-square error is obtained, that allows to evaluate the influence of noises in a channel. Possible generalizations of the formulated problem are presented.
    • TRANSMISSION OF RADIOMETER DATA FROM THE SYNCHRONOUS METEOROLOGICAL SATELLITE

      Davies, Richard S.; Philco-Ford Corporation (International Foundation for Telemetering, 1973-10)
      The Synchronous Meteorological Satellite uses a spin scanner radiometer which generates eight visual signals and two infrared signals. These signals are multiplexed and converted into a 28-Mbps data stream. This signal is transmitted to ground by quadriphase modulation at 1686.1 MHz. On the ground, the digital signal is reconstructed to an analog signal. To conserve bandwidth, an analog-to-digital converter with a nonlinear transfer function was used for the visual signals. The size of the quantization step was made proportional to the noise output of the scanner photomultiplier tube which increases as the square root of incident light. The radiometer data transmission link was simulated on a digital computer to determine the transfer function. Some results of the simulation are shown.
    • UNIVERSAL AIR-GROUND DATA LINK SYSTEM

      Williamson, Thomas; Federal Aviation Administration (International Foundation for Telemetering, 1973-10)
      With the implementation of a nationwide Air Traffic Control (ATC) automation system nearly completed the Department of Transportation/Federal Aviation Administration is devoting considerable attention to the integration of a data link capability into the system. This paper presents a description of the universal data link system and details of the system’s characteristics. A possible configuration of the data link system with the ATC automation system is also presented.
    • ON DETERMINATION OF OPTIMAL ACCUMULATION TIME IN PARTICLE FLUX REGISTRATION

      Babkin, V. F.; Institute for Space Research (International Foundation for Telemetering, 1973-10)
      Poisson particle flux is considered which intensity is a random process. The equations are presented for the construction of the intensity realization estimate corresponding to the minimum of a mean-square reconstruction error. The condition is derived the filfulment of which assures the existence of the optimal accumulation time minimising the reconstruction error. The calculation results are given to illustrate the dependence of a mean-square reconstruction error on the accumulation time.
    • MILITARY COMMUNICATION SATELLITES

      Wall, Virgil W.; The Aerospace Corporation (International Foundation for Telemetering, 1973-10)
    • THE ATS-F RADIO FREQUENCY INTERFERENCE MEASUREMENT EXPERIMENT

      Henry, Varice F.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
    • THE NEED TO MEASURE MAN-MADE RADIATION FROM ORBIT FOR SPECTRUM MANAGEMENT

      Eckerman, Jerome; Wolff, Edward A.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
    • RELAY TECHNIQUES FOR MOBILE SERVICES

      Vandenkerckhove, J.; ESRO/ESTEC (International Foundation for Telemetering, 1973-10)
      Dr. Vandenkerckhove will discuss system considerations involved in providing communications services to aeronautical and maritime users via Synchronous Relay Satellite.
    • International Telemetering Conference Proceedings, Volume 09 (1973)

      International Foundation for Telemetering, 1973-10
    • RFI ANALYSIS APPLIED TO THE TDRSS SYSTEM

      Jenny, J.A.; ESL Incorporated (International Foundation for Telemetering, 1973-10)
      The effect of radio frequency interference (RFI) on the proposed Tracking and Data Relay Satellite System (TDRSS) was assessed. The method of assessing RFI was to create a discrete emitter listing containing all the required parameters of transmitters in the applicable VHF and UHF frequency bands. The transmitter and spacecraft receiver characteristics were used to calculate the RFI contribution due to each emitter. The individual contributions were summed to obtain the total impact in the operational bandwidth. Using an as yet incomplete enitter base, we have concluded that the 136-137 MHz band should be used by TDRS rather than the whole 136-138 MHz band because of the higher interference levels in the 137-138 MHz band. Even when restricting the link to 136 to 137 MHz, the existing link design is marginal and it is recommended that interference reduction units, such as the Adaptive Digital Filter, be incorporated in the TDRS ground station. RFI is less of a problem in the 400.5 to 401.5 MHz band and can probably be handled by restricting command transmissions to low RFI areas or if that is not acceptable, by using simple automatic notch filters to notch out the few interferers present.
    • THE REDUNDANCY OF A SIMPLE SYNCHRONIZATION METHOD FOR VARIABLE LENGTH CODES

      Shtarkov, Yu. M.; Academy of Sciences of the USSR (International Foundation for Telemetering, 1973-10)
      Prefix insertion prior to the coded representation of every fixed length block of data provides a simple synchronization method for variable length coding. Unlike fixed length coding where the prefix appears with a set period, the appearance time of each prefix word in the variable length coded representation is a random variable. At the receiver a synchronization decision is made whenever a pattern within a threshold Hamming distance of the prefix is received. In this paper an expression is found for small synchronization error probabilities. This egression depends on the coded block length only through its average value L. The optimal value for the recognition threshold is found. The necessary and sufficient condition for an arbitrarily small synchronization error probability is shown to be that the prefix length grows as log L. The results are discussed from the viewpoint of data compression and source encoding.
    • 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 SHOCK HARDENED PCM SYSTEM WITH DATA STORAGE

      Barnes, D. E.; Sandia Laboratories (International Foundation for Telemetering, 1973-10)
      A miniature shock hardened PCM system with data storage capability has been developed by Sandia Laboratories for use in test where RF transmission either difficult or impossible. The PCM has 16 channel input capacity and encodes the data with 6 bit accuracy. The data rate is selectable from 1k bit per second to 250 k bit per second. The encoder has been harbarized and packaged in a volume of less than 4 cubic inches. The data storage is selected in 6 k bit increments with a maximum storage of 600 k bits. Typical applications involving earth and water penetrating are described.
    • A MULTI-PURPOSE, DUAL-CHANNEL MODEM FOR C/No THRESHOLD

      Baghdady, Elie J.; Info Systems (International Foundation for Telemetering, 1973-10)
      A description is given of a newly developed modem based on the synthesis of a constant-envelope quadra-phase signal with dual-channel frequencydivision multiplexing of analogvoice with data, data with data, time code With data, ranging signal with d:Ata, etc. The technique is capable of providing low-threshold operation down to carrier power-to-(noice power density) ratios, about 40 db, and includes a built-in, on-line measurement and display of the C/N(o) for quantitative performance monitoring purposes.
    • 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.