• International Telemetering Conference Proceedings, Volume 08 (1972)

      International Foundation for Telemetering, 1972-10
    • BIT SYNCHRONIZATION

      McRae, D. D.; Smith, E. F.; Radiation Incorporated (International Foundation for Telemetering, 1972-10)
      In this paper the trade off between acquisition and noise performance for several bit synchronizer techniques are examined. Results are presented for random NRZ input data with an initial frequency offset between the incoming bit rate and the a priori estimate of this rate.
    • FIBER OPTICS COMMUNICATIONS

      Somekh, S.; Yariv, A.; California Institute of Technology (International Foundation for Telemetering, 1972-10)
      The transfer of information in the form of light waves via an optical fiber waveguide is discussed. Small size and weight together with high information rate capability make the fibers attractive for various types of communications systems. Description of channel characteristics such as attenuation and bandwidth is given, and possible input and output devices are examined.
    • MICROPROGRAMMABLE PROCESSORS APPLIED TO TELEMETRY PROCESSING SYSTEMS

      Karleskint, Daniel J. (International Foundation for Telemetering, 1972-10)
      This paper briefly analyzes the application of modern microprogram techniques in the computerized telemetry processing environment. It shows these technique s can attain a flexibility in design and application previously unavailable.
    • A NEW TYPE OF PSK ANTI-AMBIGUITY SYSTEM FOR SATELLITE APPLICATIONS

      Pera, L.; European Space Technology Centre (ESTEC) (International Foundation for Telemetering, 1972-10)
      In coherent PCM-PSK links the problem of solving the phase ambiguity in the reconstruction of the subcarrier has been traditionally solved by making use of the knowledge of some part of the transmitted message or by employing MARK-type codes. After a brief discussion of these well-known methods a new approach is proposed which makes use of an auxiliary non-ambiguous PSK demodulator based on the estimation of the sign of the message transitions. It is shown that no particular requirements on the noise performance of this auxiliary demodulator is needed to ensure acceptable overall performance of the antiambiguity system. A particularly simple hardware implementation is indicated and experimental results are presented for cases of practical interest.
    • COMPARING BANDWIDTH REQUIREMENTS FOR DIGITAL BASEBAND SIGNALS

      Houts, R. C.; Green, T. A.; University of Alabama (International Foundation for Telemetering, 1972-10)
      This paper describes the relative, bandwidth requirements of the common digital baseband signaling techniques used for data transmission. Bandwidth considerations include the percentage of total power in a properly encoded PN sequence passed at bandwidths of 0.5, 1, 2 and 3 times the reciprocal of the bit interval, T(b). The signals considered in this study are limited to the binary class, i.e., each decision at the receiver yields one bit of information, in contrast to signaling schemes which encode groups of bits into a given signal amplitude, phase shift, etc. The study compares such signaling techniques as delay modulation (DM), bipolar (BP), biternary (BT), duobinary (DB), pair selected ternary (PST), and time polarity control (TPC) in addition to the conventional NRZ, RZ and BIΦ schemes. It is shown that several of the signals can be transmitted over channels which block frequencies below 10% of the bit rate and still lose less than 5% of the total signal power. Based upon the dual consideration of a large number of regularily-spaced level transitions to assure synchronization plus a minimum of bandwidth and no dc response, it is concluded that DM and PST are the best choices.
    • A REAL TIME MULTIPROGRAMMED TELEMETRY SYSTEM

      Muse, G. B. (International Foundation for Telemetering, 1972-10)
      A study of several Telemetry Data Reduction Systems has revealed some common problems which reduce the effectiveness of these systems. The problems include: The high cost of real-time computer analysis programs, lengthy turnaround for data product modification, lack of testing flexibility, and reduced hardware system utilization. A computer system, 11TELFILE11, has been implemented to improve upon these problem areas. This system is operational at the Space and Missile Test Center (SAMTEC), Vandenberg Air Force Base, for support of the Minuteman III Weapons Systems.
    • EXPERIMENTAL COMPARISONS OF TELEVISION TRANSMISSION TECHNIQUES

      Perkins, F. A.; Proctor, J. A.; Harris-Intertype Corporation (International Foundation for Telemetering, 1972-10)
      The performance of a television transmission system is ultimately measured by the subjective judgment of the viewer. For different processing techniques, this subjective judgment may not agree with objective measures such as output signal-to-noise ratio. This is particularly true when comparing analog and digital techniques, since the nature of the noise and distortion is quite different. A number of analyses have compared various modulation and processing techniques on the basis of qualitative characteristics. This paper provides data for subjective comparisons of several analog and digital techniques. The cooperation of the NASA Manned Spacecraft Center in allowing use of equipment being built and tested for them is gratefully acknowledged.
    • PHASE DISTORTION IN MAGNETIC TAPE RECORDERS

      Hedeman, W. R., Jr.; The Aerospace Corporation (International Foundation for Telemetering, 1972-10)
      Phase distortion due to the record/reproduce process, independent of electronics, is experimentally established and measured. It is found to be a function of the record gap length. Phase compatibility between recorder/reproducers requires either record amplifier phase correction for each tape speed or standardization of record gap.
    • A DISTRIBUTION CONTROL UNIT FOR SATELLITE-SWITCHED COMMUNICATIONS

      Cooperman, R.; Dobyns, T.; Communications Satellite Corporation (International Foundation for Telemetering, 1972-10)
      Traffic estimates for the next generation of commercial communications satellites strongly indicate the desirability of using highly directive multibeam antennas to increase channel capacity. This antenna configuration allows multiple access via space division and frequency sharing through the isolation inherent in the directive multibeam antenna. Coupling this technique with a satellite-borne programmable communications distribution subsystem results in a highly efficient system. The distribution subsystem, consisting of a distribution control unit (DCU) and microwave switch matrix (MSM), is introduced into the satellite communications equipment prior to the output amplifiers and enables interconnection between all earth terminals accessing the satellite. Data on the traffic flow allocation required to provide service is stored in an onboard memory and is used to directly control MSM operation.. Flexibility to adapt to changes in traffic flow patterns is achieved through ground command of the onboard memory contents. A detailed description of the DCU and a general discussion of the space segment are provided.
    • THE ROLE OF PARTIAL CORRELATION IN MULTIPLE ACCESS

      Anderson, D. R.; TRW System (International Foundation for Telemetering, 1972-10)
      This paper presents results on the partial correlation properties of PN and frequency-hopping sequences considered as multiple access address signals.
    • IMPACT OF SOLAR CALIBRATION ON TELEMETRY SYSTEM TESTING AND CHECKOUT

      Crane, Williams S.; Pickett, Robert B.; ITT-Federal Electric Corporation (International Foundation for Telemetering, 1972-10)
      The advent of solar calibration techniques has resulted in a drim--tic reduction in the time required to conduct telemetry antenna system measurements. Solar calibration provides a rapid, simple and accurate means of determining antenna system performance in the field environment. A program of solar calibration was instituted two years ago at the SAMTEC Western Test Range (WTR) as a basis for calibration,.trouble shooting, operational planning and determining premission “Go/No-go” status. Solar testing has assisted the site personnel in decreasing the time required for system performance tests, preventative maintenance, premission checkout and trouble isolation. The results obtained are more accurate than the laboratory or antenna field measurements for the determination of either gain or system noise temperature independently. In most cases, measurements provide absolute values within ±1 db accuracy. The Figure of Merit (M = G/T(s)) is now a required data item for some missions and is requested by the range user to assist in his data evaluation.
    • RECENT DEVELOPMENT RESULTS ON THE HELIOS S-BAND COMMAND RECEIVER

      Heynisch, B.; AEG-TELEFUNKEN (International Foundation for Telemetering, 1972-10)
      By joint effort of the US and West Germany a Sunprobe will be launched by 1974 named HELIOS. In the Telecommunications Subsystem the Telecommand Receiver has a keyrole as Experiments have to be switched up to 2 AU distance from earth. The input power at the Receiver Equipment input terminal is -147 dbm with SNR of 6 db in 2 BL(o) = 32,5 Hz Loop Bandwidth. To achieve this sensitivity a Receiver in Phaselocked loop techniques with a low noise Preamplifier had to be developed. In cooperation and with consultance of well known US-Scientists it was possible to design and develope the S-Band Receiver up to the Qualifikation Model in less than two years. This report shall give a survey over concept and design of the receiver and some special experiences during development and integration tests.
    • DYNAMIC REQUIREMENTS FOR DIVERSITY COMBINERS

      Streich, R. G.; Little, D. E.; Pickett, R. B.; ITT-Federal Electric Corporation (International Foundation for Telemetering, 1972-10)
      In order to provide nearly continuous data on missile and Space launches, polarization diversity is utilized at acquisition sites. Diversity signals are also combined to further reduce data dropouts. It is shown in this report that the right hand circular (RHC) and left hand circular (LHC) signals undergo rapid transients during certain portions of the flight, and that the channel dropouts are sometimes independent. The nature of the transients is described and a test set which simulates the transients discussed. Finally bench test data is compared with flight test data to verify that combiners with rapid transient response are required to cope with the RF transients.
    • IMPROVEMENTS IN DEEP-SPACE TRACKING BY USE OF THIRD-ORDER LOOPS

      Tausworthe, R. C.; Crow, R. S.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1972-10)
      Third-order phase-locked receivers have not yet found wide application in deep-space communications systems because the second-order systems now used have performed adequately on past spacecraft missions. However, a survey of the doppler profiles for future missions shows that an unaided second-order loop may be unable to perform within reasonable error bounds. This article discusses the characteristics of a simple third-order extension to present second-order systems that not only extends doppler -tracking capability, but widens the pull-in range and decreases pull-in time as well.
    • EFFECTS OF TAPE FLUTTER ON NOTCH NOISE LOADING TEST PERFORMANCE OF PREDETECTION RECORDING OF A FREQUENCY MODULATED CARRIER

      Hedeman, W. R.; Nichols, M. H.; Aerospace Corporation (International Foundation for Telemetering, 1972-10)
      IRIG Document #L18-71 “Test Methods for Telemetry Systems and Subsystems” lists the notch noise loading test for establishing a figure-of-merit for frequency division systems. This paper reports measured effects of tape flutter on notch noise test data on pre-detection tape recorded FM carriers. The effects are explained on the basis of spectra of the output of the FM demodulator. The principal effect is to reduce the measured noise power ratio, NPR, in those notches at the low end of the baseband which overlap the flutter spectrum. The effect of tape flutter on FM/FM systems is reviewed.
    • DIGITALLY IMPLEMENTED CLOCK ACQUISITION LOOPS FOR LOW SNR DATA SIGNALS

      Schoolcraft, R. W.; Magnavox Research Laboratories (International Foundation for Telemetering, 1972-10)
      The development of powerful error correction codes for binary data channels has generated a requirement for high performance clock acquisition loops. These loops must provide clean estimates of the data clock at very low data SNR in order to prevent dissipation of the coding gain through noise in the data recovery timing. The key element in high performance clock loops is the method of extracting clock information from the received data stream. Three loops are described which illustrate several extraction concepts and which can be used as design guides. The first loop extracts clock information by use of the function D(t)•D(t+ T/2). The extractor is implemented almost entirely with digital logic elements and is very compact. The third loop is extremely efficient due to the use of a time window which is open for only a short time around the transitions of the data. Its implementation is heavily analog. The second loop is a hybrid of the first and the third falls between them in both performance and complexity. Performance curves are presented for the three loops in terms of data SNR degradation as a function of data SNR and loop bandwidth. Experimental data is presented for the first loop.
    • CHARACTERISTICS OF PHASE DETECTORS IN PRESENCE OF NOISE

      Pouzet, A. H. (International Foundation for Telemetering, 1972-10)
      The phase detector is an important device used extensively in phase locked loops and in coherent detectors. Its characteristics must be known to predict the behaviour of the phase locked loop especially by non linear analysis. Noiseless analysis has been made for great varieties of phase detectors, but a satisfactory analysis in presence of noise is still needed. Many authors make the implicite assumption that the characteristics in presence of noise and without noise are alike, what is wrong. In fact it will be shown that all phase detector characteristics become sinusoidal at low signal to noise ratios whatever their noiseless characteristic may be. Besides, it will also be shown that when used as coherent detectors, sinusoidal phase detectors are better than linear phase detectors regarding the output signal to noise ratio, and output signal to noise spectral density ratio.
    • A TELECOMMUNICATIONS LINK MODEL FOR DEEP SPACE, WITH APPLICATIONS TO THE HELIOS PROBE

      Stolle, Ernst; Deutsche Forschungs-und Versuchsanstalt fur Luft-und Raumfahrt (International Foundation for Telemetering, 1972-10)
      The concept of the coherent PCM/PSK/PM telecommunication system of the US/German solar probe mission HELIOS is presented. Subsystem performance models are given for the telemetry link using theoretical, simulation, and measurement results, to obtain a realistic approximation to the over-all link performance. After the system description, performance/ efficiency models are discussed for the (sequential) data decoder, symbol synchronizer, subcarrier and RF demodulation, and waveform distortion. The integrated over-all link model is then applied to minimizing the total signal-to-noise ratio requirement at receiver input. Examples from the HELIOS link design demonstrate the feasability of the approach.
    • A NEW VHF-INTERFEROMETER WITH THREE STEERABLE HIGH-GAIN-ANTENNAS FOR SATELLITE-TRACKING

      Fogy, W.; German Aero-Space-Research Establishment (International Foundation for Telemetering, 1972-10)
      The German-Central-Ground-Station near Weilheim, Bavaria, called Z-DBS, operates now on VHF-Telemetry and Telecommand. Its monopulse-autotrack-subsystem measures one way doppler datas and medium-precise (~0,25° RMS) direction angular (AZ,EL) datas. For precise orbital tracking the station will now be completed by a VHF-Interferometer with three steerable high-gain-antennas, using the angular information of the existing system for initial acquisition and ambiguity resolution. Such a system is applicable to track most near-earth-satellites in orbit without needing a global network even with a relatively low percentage of contact time because of its large angular- and distance-coverage from one topos. The interferometer, now under construction, will be ready for operation at the end of 1973. The present paper gives a brief description of the parameter requirements, the system itself and the methods used to overcome the very high technical difficulties. The total residual direction error is predicted not to exceed (10÷15)”, including nearby ground reflexions but excluding residual athmospheric propagation effects. High side-lobe-suppression-antennas with extremly stable phase characteristics as well as a 3-channel-piloting-receiver-system are used to make the antenna’s difference-phase errors small enough and to eliminate phase changes throughout long cables and receivers. A computer operates the whole system to a high degree of automacy and evaluates and smoothes the direction datas.