• L-ORTHOGONAL SIGNAL TRANSMISSION AND DETECTION

      Lindsey, W. C.; Simon, M. K. (International Foundation for Telemetering, 1972-10)
      This paper investigates the detailed capabilities and performance characterization of systems that employ L-orthogonal signaling techniques. L-orthogonal signals represent a unified set of signals wherein the polyphase and orthogonal (bi-orthogonal) signal sets are included as special cases. This fact is important since orthogonal (bi-orthogonal) and polyphase signaling sets r e present opposing forces as far as tradeoffs between error probability, energy - to-noise ratio, and bandwidth requirements are concerned. Bounds on the performance of the optimum receive r and the performance of various suboptimum (practical) receiver structures are given. Coherent and differentially coherent detection of differentially encoded signals re also pursued. Various comparisons and tradeoffs are made by means of numerical evaluation of the error probability expressions.
    • 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.
    • DEMODULATION OF FM SIGNALS BY A DISCRETE PHASE LOCKED LOOP

      Reddy, C. P.; Gupta, S. C.; SMU Institute of Technology (International Foundation for Telemetering, 1972-10)
      This paper discusses the discrete-phase locked loop for demodulation of an incoming frequency modulated analog signal imbedded in white noise. The discrete samples admitted into the system adoptively, represent an estimate of the message at the discrete instants of time which can be improved further with a correction factor. The work is in two parts: (1) even without the noise, perfect demodulation is not possible. To arrive at the best estimate, requirements are specified regarding the ratio of carrier frequency to maximum frequency deviation, taking into consideration the lock range and the Nyquist sample rate. A simulation study is performed to specify the bounds for the estimate to be accurate enough. (2) With the above considerations, the receiver is analyzed with noise. For high carrier to noise ratio, it is shown that the performance is at least as good as an analog discriminator. The only requirement being that the condition specified in (1) is more stringent. Digital computer solutions of the system check the above and provide a qualitative picture of the threshold behavior comparable to analog feedback discriminators.
    • DATA COMPRESSION FOR EARTH RESOURCES SATELLITES

      May, C. L.; Spencer, D. J.; TRW Systems (International Foundation for Telemetering, 1972-10)
      This paper concerns an information-preserving data technique which is applicable to multi-spectral imagery such as that obtained by earth-resources satellites. The requirements for data compression in such missions is discussed and a rationale is presented for the use of distortion-free information-preserving compression. The selected compression technique involves the use of the spectralspatial-delta-interleave (SSDI) algorithm, a form of DPCM, to eliminate gross spectral and spatial redundancies. This reduced data is then coded for transmission using either the Huffman or the Rice coding algorithms. The coding algorithms have been simulated using a portion of frame 3698 taken during the Apollo S065 experiment and, the results are presented. A parametric study presents the compression achieved by the SSDI-Rice algorithm as a function of block size and split-pixel mode used. Implementation considerations are also given.
    • SELF-CORRECTING DIFFERENTIAL PCM

      Anglade, P.; Hawkes, T. A.; Durand, J. J. (International Foundation for Telemetering, 1972-10)
      Differential PCM (DPCM) systems are characterized by an accumulation of transmission errors in the signal regenerated in the receiver. The use of a normalization procedure before transmission appears to permit suppression of these errors. This normalization must be carried out with respect to the limit value toward which the signal is evolving. The error reduction is not immediate, but is a function of signal value and signal activity. For constant signals there is no reduction. Reduction is more rapid the more widely the signal varies, and is also more rapid as the frequency of signal reversals increases. This method of coding requires adaptation to each application, since the basic quantization interval varies with signal magnitude.
    • 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.
    • 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.
    • 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.
    • DIGITAL FM DEMODULATION TECHNIQUES

      Garodnick, Joseph; Goldmark Communications Corp. (International Foundation for Telemetering, 1972-10)
      Digital systems have been heavily emphasized over the past decade because of their intrinsic trouble free operation, multiplexed signal handling capabilities, and the complex processing techniques possible through the use of small special and general purpose digital computers. The digital evolution has also allowed system cability to increase, while size, cost and power consumption decrease. Functions previously deemed impossible to implement are now being constructed in production facilities. When digital techniques are used for source encoding in a wide band communications network (such as two-way CATV), information is transmitted and received digitally with Small error probalility compared to analog signals, especially when carriers and media take the form of cable, laser beams and fiber optics where line repeaters are used in lieu of amplifiers.
    • 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.
    • A NARROWBAND, CRYSTAL CONTROLLED BIOMEDICAL TELEMETRY SYSTEM

      Westbrook, Richard M.; Fryer, Thomas B.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1972-10)
      A miniature, single-channel, crystal-controlled transmitter has been developed for biomedical applications. A narrowband frequency modulation (±7 kHz) of the RF is used to achieve maximum operating range with minimum transmitting power. The radiated power is limited to stay within the 50 μv/m at 15 m FCC requirement for low power transmitters (Part 15.212 FCC Regulations) in the 88 to 108 MHz band. This technique offers a number of advantages. First only manufacturer’s type approval is required for the device and the user does not need a license. Second maximum operating range can be achieved within the FCC power limitations by using a narrowband that is consistent with the required medical information bandwidth. A third advantage in using the 88 to 108 MHz band is that the commercial FM stations are relatively widely spaced and carefully regulated so that by selecting the transmitter’s frequency in the guard band between stations, minimum interference from other transmitter sources is encountered. For EKG and EEG applications, where an information bandwidth of 0.1 to 150 Hz is adequate, a subcarrier with a fixed frequency (approximately 1 kHz) is used with differential pulse width modulation (DPWM). This type of subcarrier has the advantage of simple circuitry for both the transmitter and demodulator. Since DPWM is self-aligning, it can be handled effectively by magnetic tape recorders having relatively high tape speed errors. For EMG and other high frequency data signals the RF can be directly frequency modulated without the use of a subcarrier.
    • STATISTICS FOR EFFICIENT LINEAR AND NON-LINEAR PICTURE ENCODING

      Kummerow, Thomas; Technische Universitat Braunschweig (International Foundation for Telemetering, 1972-10)
      Differential pulse code modulation (DPCM) of video signals can be improved by assuming the model of the general Markov Source, which has not only linear but also nonlinear statistical dependencies. The proposed type of coder will have a fixed code word length and synchronous bit-rate. It consists of a differential coder with linear prediction and a quantizer with an additional nonlinear coder. The nonlinear coder can be considered as changing the quantizing characteristic according to the past of the signal. The improvement over PCM and over DPCM is measured by the signal to quantizing noise ratio. Picture material under investigation consists of 4 different single frames of Standard CCIR 625- line television format with relatively high detail. Two types of linear prediction have been investigated : one dimensional (previous element) and two dimensional spatial prediction. The nonlinear coder is controlled by up to three previous elements of the same and the previous line. The measurements show an improvement over previous element DPCM of up to 9 dB S/N which would result in additional saving of 1.5 bits per coded element.
    • International Telemetering Conference Proceedings, Volume 08 (1972)

      International Foundation for Telemetering, 1972-10
    • 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.
    • 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.
    • IMPLANTABLE ULTRASONIC BLOOD FLOWMETERS

      Meindl, J. D.; Stanford University (International Foundation for Telemetering, 1972-10)
      Accurate measurement of pulsatile blood flow can be achieved on a chronic basis in research animals through the use of totally implantable ultrasonic flowmeters. The continuous wave Doppler flowmeter provides an attractive technique for measurement of flow velocity at a particular location such as the center of the lumen; the pulsed Doppler flowmeter is attractive for measurement of flow velocity distribution or profile across the vessel and lumen diameter, and hence volume flow. Both instruments can be electronically precalibrated and exhibit no baseline or scale factor changes during chronic experiments. Custom designed silicon monolithic integrated circuits offer significant advantages in reduced size and power drain as well as improved reliability in these instruments.
    • IMPLANTABLE TELEMETRY IN THE CHIMPANZEE

      Stone, H. L.; Sandler, Harold; Fryer, Tom; Marine Biomedical Institute; NASA Ames Research Center (International Foundation for Telemetering, 1972-10)
      The chimpanzee has been proposed as a possible human analogue for a myriad of human disease states. The lack of knowledge about the cardiovascular system in this animal or the cardiovascular response to stress is understandable because of the cost and handling problems with the chimpanzee. Part of this difficulty, namely handling, can be overcome with the proper selection of cardiovascular instrumentation. Implantable telemetry systems have the advantage that the animal does not have to be handled for any reason. Several animals have been successfully used with implantable telemetry units in the chest. A vigorous antibiotic therapy program must be used for the first few days after surgery, but there have not been any complications after this period of time. The life of the implanted unit has been prolonged by the use of a power switch which also allows remote collection of data. At the present time there is one such unit still functioning 14 months after implantation. The ease with which these units can be used makes them ideally suited for use in the chimpanzee. Examples of the various types of data collected are given and described briefly.
    • 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.
    • DIGITAL PHASE LOCKED LOOPS WITH SEQUENTIAL LOOP FILTERS: A CASE FOR COARSE QUANTIZATION

      Cessna, J. R.; National Oceanic and Atmospheric Administration (International Foundation for Telemetering, 1972-10)
      A class of digital phase locked loops exists for which performance can be demonstrated to be comparable to that of the linear analog model, yet the use of coarse quantization seems to be favored. This class is characterized by the use of (1) a phase detector with quantized output, (2) a sequential loop filter, and (3) a discrete phase adjustment clock. The sequential filter is an inherently nonlinear device which operates on a sequence of inputs and provides a sequence of outputs, usually fewer in number and with a variable interval between outputs. Operation of these loops is decidedly nonlinear and a conventional linear loop bandwidth cannot be defined. Although higher than first order loops of this class may be constructed, their analysis, so far, has been limited to first order types by random walk techniques. A quasi-bandwidth measure can be defined for these loops in terms of their transient response which serves as an absolute basis for comparison of different digital loops. Using this tool, examples of 3- and 4-level quantization in these loops are found to have no obvious advantages over the binary quantized model and in some cases striking disadvantages.