• 10-MICROMETER BAND COMMUNICATION TERMINALS IN SPACE

      McAVOY, N.; Goddard Space Flight Center (International Foundation for Telemetering, 1972-10)
      10-micrometer band communication systems using CO2 lasers for space to space links are discussed. Particular emphasis is on low earth orbiting earth observation satellites to geosynchronous satellites at high data rate. Four key technology areas are discussed: Wideband mixers for Doppler tracking; tunable laser local oscillators; high data rate modulators; laser transmitters.
    • A 10.6 MICROMETER LASER COMMUNICATION SYSTEM FOR TERRESTRIAL USE

      Goodwin, F. E.; Hughes Research Laboratories (International Foundation for Telemetering, 1972-10)
      This paper reports the development of an experimental type 10.6 μm laser communication system consisting of a transmitting terminal and a receiving terminal designed to operate one way over a nominal five mile terrestrial path. The system will provide a 5 Mbit/sec digital data channel utilizing intra-cavity optical frequency modulation, or frequency shift keying modulation format. It uses optical heterodyne detection with a mercury cadmium telluride detector operating at a temperature of 77°K and an i.f. frequency of 30 MHz. Since the system operates from fixed (non-mobile) terminals, acquisition and alignment procedures are simplified. Predicted performance in rain and fog is discussed and compared with a limited amount of actual data.
    • ADAPTIVE LINE BY LINE ENCODER FOR IMAGE TRANSMISSION

      Algazi, V. R.; University of California at Davis (International Foundation for Telemetering, 1972-10)
      A simple adaptive algorithm is applied to the line by line encoding of images. Among its desirable properties the algorithm includes a control of encoding errors independently of the image statistics. This block transform encoder, because of its adaptive nature gives rise to non-stationary errors and end of block effects. Two methods are proposed to reduce these effects and thus improve the subjective quality of reconstructed images. The performance of the algorithm is image dependent and several illustrative examples are given.
    • AIRBORNE VISIBLE LASER OPTICAL COMMUNICATION EXPERIMENT

      Randall, J. L.; Marshall Space Flight Center (International Foundation for Telemetering, 1972-10)
      A series of optical communication experiments between a high altitude aircraft at 18.3 km (60,000 ft) and a ground station are planned by NASA in the summer of 1972. The basic concept is that an optical tracker and transmitter will be located in each terminal. The aircraft transceiver consists of a 5-mW HeNe laser transmitter with a 30-megabit (Mbit) modulator. The ground station beacon is an argon laser operating at 488 mn. A separate pulsed laser radar is used for initial acquisition. The objective of the experiment is to obtain engineering data on the precision tracking and communication system performance at both terminals. Atmospheric effects on the system performance are of prime importance.
    • AN ALL DIGITAL PHASE LOCKED LOOP

      Greco, J.; Garodnick, J.; Schilling, D. L.; City College of CUNY (International Foundation for Telemetering, 1972-10)
      An All Digital Phase Locked Loop for FM Demodulation is presented. The system operates synchronously and performs all required digital calculations within one sampling period, thereby performing as a real time special purpose computer. The signal to noise ratio is computed for frequency offsets and sinusoidal modulation and experimental results verify the theoretical calculations.
    • ALL-DIGITAL COHERENT DEMODULATOR TECHNIQUES

      Natali, Francis D.; Philco-Ford Corporation (International Foundation for Telemetering, 1972-10)
      This paper discusses all-digital techniques for receiving and coherently detecting moderate data rate (less than 1 Mbps) PSK signals in real time. A receiver employing synchronous bandpass sampling and A/D conversion of the IF signal is described. Sampler synchronization, bit synchronization, and data detection are performed by a special-purpose digital processor. Analytical methods are developed for predicting receiver performance, and experimental data is presented to indicate the degree of agreement that one might expect.
    • AMPLITUDE-PHASE-KEYING WITH M-ARY ALPHABETS: A TECHNIQUE FOR BANDWIDTH REDUCTION

      Thomas, C. M.; TRW Systems (International Foundation for Telemetering, 1972-10)
      The spectral occupancy of transmitted digital data can be reduced by employing symbols from an M-ary alphabet. A modulation technique combining both amplitude and phase keying (APK) requires less peak and average power than M-ary PSK to achieve the same symbol error probability. Efficient signal set designs have been found by an empirical search of a large number of candidate sets with a comparison based on symbol error probability. New 8-ary and 16-ary designs are presented which outperform previously suggested designs on both a peak and average SNR basis. The bandwidth efficiency of the principal APK sets and PSK is presented as a function of alphabet size (4-ary to 128-ary) to illustrate the bandwidth-power tradeoff.
    • “ANIK” SATELLITE COMMUNICATIONS SYSTEM

      Houterman, M. J.; Hughes Aircraft Company (International Foundation for Telemetering, 1972-10)
      The Canadian Domestic Communications Satellite, “ANIK”, which is scheduled for launch in November 1972, will become the space segment of the first domestic geostationary satellite system. The satellite communication system consists of an all microwave 12 channel repeater in conjunction with a 60 in. shaped beam solar transparent parabolic reflector and associated feed. This paper discusses the “ANIK” satellite communication system design. Overall system performance parameters, including G/T and EIRP coverage of Canada, are presented. The repeater is broken down into three major items; wideband receiver, multiplexers, and channel amplifiers. Typical performance data is given for each of these items. The antenna design is considered and the receive and transmit feed networks are presented. Emphasis is placed on the dual mode nature of the transmit function of the antenna.
    • APPENDIX A: Eleventh Annual Report of the Telemetering Standards Coordination Committee

      Pruss, Hugh; Telemetering Standards Coordination Committee (International Foundation for Telemetering, 1972-10)
      Since its beginning in 1960 the TSCC has for the most part concentrated its efforts in reviewing standards published by the Range Commanders Council, IRIG. These reviews and resulting recommendations occurred prior to formal publication or formalization of the standard. It is also gratifying to note that most of the recommendations made were accepted for adoption in the printing of the standards. In its desire to serve all facets of the Telemetering Community, the T. S. C. C. began looking into the activities of other established Governmental Agencies, besides the D. O. D., who might benefit from assistance in the form of specification reviews by the T. S. C. C.. Subsequently, the T. S. C. C. took a long "look around" and discovered that NASA, GSFC was concerning itself with tracking and data acquisition system standards as they relate to new DSN/NASA needs for the current and forthcoming Space & Earth Sciences experiments. An offer of assistance was presented to NASA, GSFC in July of. 1971 and this was subsequently accepted by letter dated 8 September 1971 from the NASA/GSFC Data Systems Requirement Committee, Advanced Data Systems Division, Mission and Data Operations Directorate.
    • APPLICATION OF RANGE COMMANDERS COUNCIL DOCUMENT 118-71 TEST METHODS TO RANGE MANAGEMENT-SAMTEC

      Radom, Stanley R.; Vandenberg Air Force Base (International Foundation for Telemetering, 1972-10)
      Range management techniques utilized by the SAMTEC enable telemetry system and subsystems to be validated for operational support readiness. Application of test methods from Range Commanders council Document 118-71 are described for solar calibration of the telemetry receiving system, PCM bit error rate and FM noise power ratio testing. Limitations of noise power ratio testing is described including need for additional range user performance requirements. The use of test results provides SAMTEC range management with a near realtime certification of telemetry system performance accuracies. System performance levels are established which provide a “red flag” indicator to alert range management that systems are below the norms expected. Application of the test methods and the use of the red flag provides the SAMTEC range management the decision making information required to employ minimal telemetry systems and manpower resources in the effective achievement of range user program support requirements. These test methods will be used to establish the data base for scoring the range technical support contractors performance incentive fee. An additional benefit of the test methods is their application for the test and acceptance of new telemetry systems and subsystem.
    • BANDWIDTH EFFICIENCY FOR DIGITAL COMMUNICATION VIA A HARD LIMITING CHANNEL

      Cahn, C. R.; Moore, C. R.; Magnavox Research Laboratories; North American Rockwell (International Foundation for Telemetering, 1972-10)
      The achievable burst data rate with typical channel filters is obtained for biphase, quadriphase, and eight-phase modulation. The effect of intersymbol interference in a hard-limiting channel is modeled by a time-domain representation which averages probability of error over all (truncat, ed) equally likely sequences of digits. As measured by the bit rate per unit bandwidth achieved at a given received E(b)/N(o), quadriphase outperforms biphase, but by less than a factor two, in contrast to behavior in a linear channel. Eight phase modulation appears to offer only a marginal improvement over quadriphase, and only for E(b)/N(o) > 15 db.
    • BIOTELEMETRY IN THE 1970’S

      Rader, D. R.; University of Southern California (International Foundation for Telemetering, 1972-10)
      A date cannot be pinpointed for the concept of using telemetry for acquiring biological data; however, it is known that the birth of biotelemetry in the form of hardware occurred about 1921--with the report of a heart sound transmitter. Biotelemetry matured only slightly from the twenties to the early fifties. During the fifties and sixties large amounts of money were administered through the money pipeline of the federal government. As a consequence, the growth during this period was bath rapid and grotesque, with tentacles reaching into scores of industrial and educational institutions. Duplication of efforts was quite common during this period and hundreds of miniature biotelemetry systems were built, but results deriving from practical application were quite limited. During the last few years, much of the chaff was shucked from this new growth, a root system developed, and biotelemetry found limited use as a tool in clinical medicine and in medical research. In the past biotelemetry has not lived up to the expectations. What about the future--will it really occupy an important place in clinical medicine and medical research? What is the economic outlook--how many jobs will it support? Which areas will require new talent? And, finally, what are the most common problems and haw can they be solved?
    • 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.
    • CHANNELIZATION AND CHANNEL MONITORING IN FDMA COMMUNICATIONS

      Gagliardi, R. M.; University of Southern California (International Foundation for Telemetering, 1972-10)
      In this paper the concept of spacecraft self-regulation of downlink power output is investigated for a hypothetical frequency division multiple access (FDMA) communication net. In this operation channels are filtered off (channelization) and monitored to determine those channels that are inactive; i.e., not transmitting. The results of the activity survey are then used to control channel gain in the spacecraft and regulate the drive power into the output amplifier. In this way, available repeater power normally not used during periods of low activity can be redistributed over the active channels to improve their performance. For maximum improvement, this requires not only adjustment of the individual channel gains, but removal of the inactive channels from the limiter. Equations are developed which are useful for system design and aid in the evaluation of resulting system performance and assessment of feasibility of implementation.
    • 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.
    • 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.
    • COMPARISON OF DIGITAL MODULATION METHODS

      Goodman, David J.; Bell Laboratories (International Foundation for Telemetering, 1972-10)
      Important characteristics of a digital modulation technique are economy, efficiency, and quantizing distortion. As in most engineering situations, the choice of a specific digital modulation method for a practical application represents a compromise among cost and performance objectives. The purpose of this paper is to identify important design variables of digital modulators and to discuss the manner in which they influence cost and performance. In particular, we derive formulas that show the variation of quantizing noise with sampling rate and quantizer resolution in basic PCM and DPCM modulators. These formulas imply a conflict between economy and efficiency and we describe three current approaches to the resolution of this conflict. The first is efficiency oriented, the second economy oriented, and the third relies on digital signal processing to convert between efficient and economical modulation formats.
    • THE COMPLEX DIGITAL FILTER AND ITS APPLICATIONS IN DIGITAL SIGNAL PROCESSING

      Lebowitz, S. H.; Computer Sciences Corporation (International Foundation for Telemetering, 1972-10)
      Digital computer simulation of communication systems have been gaining wide acceptance and usage as a tool for analysis. In some cases, when the number of independent parameters is large or the processes are highly nonlinear, it is the only viable technique. In most digital computer simulations, the digital representation of bandpass filters can impose serious synthesis problems when conventional digital filter synthesis techniques are utilized. It is shown that the use of a complex (real and imaginary) technique of digital filter synthesis can eliminate several of the synthesis problems associated with conventional techniques. Three applications of the com lex technique are described in this paper. The three applications discussed in this paper are listed below with a short description of each. 1. A lowpass-to-bandpass transformation is described that preserves all lowpass characteristics of the filter. For instance the gain and group delay functions remain symmetrical for any center frequency and bandwidth. 2. The synthesis of analytic representations of real signals can be easily achieved by the use of a complex digital filter. An important advantage of analytic signals is that their envelope and phase are instantaneously available. 3. Equalization of bandpass characteristics can be effected at lowpass and then shifted to the proper frequency without any undesirable warping effects. Complex digital filter synthesis has been described previously, but very little emphasis has been placed on the application of this technique. Advances in the art of miniature high speed digital circuitry will allow the advantages of complex filtering to be realized in actual systems as well as digital simulations.
    • COMPUTER NETWORK DESIGN PRINCIPLES DERIVED FROM EXPERIENCE AND MEASUREMENTS ON THE ARPA NETWORK

      Kleinrock, Leonard; University of California (International Foundation for Telemetering, 1972-10)
      The design of the ARPA experimental computer network was a distributed effort which benefited from the talents of many people working both in concert and independently. In this paper we discuss some of the principles of design which have evolved from that effort. The measures, models and analytical results from design are further compared to simulation and measurement of the network itself; this permits us to evaluate the design tools themselves. We find that these principles are applicable to message-switching networks in general, and therefore the scope of this paper goes beyond that of the ARPA network.
    • CONCATENATED CODING FOR LOW DATE RATE SPACE COMMUNICATIONS

      Chen, C. H.; Southeastern Massachusetts University (International Foundation for Telemetering, 1972-10)
      In deep space communications with distant planets, the data rate as well as the operating signal-to-noise ratio may be very low. To maintain the error rate also at a very low level, it is necessary to use a sophisticated coding system (longer code) without excessive decoding complexity. The concatenated coding has been shown to meet such requirements in that the error rate decreases exponentially with the overall length of the code while the decoder complexity increases only algebraically. Three methods of concatenating an inner code with an outer code are considered. Performance comparison of the three concatenated codes is made. It is shown that the concatenated code with inner code a convolutional code and outer code a Reed-Solomon code performs the best among the three.