• Feedback in Data Transmission

      Ebert, P. M.; Bell Telephone Laboratories (International Foundation for Telemetering, 1970-10)
      A survey of the possible gains to be realized by the use of various feedback techniques is given. Noiseless information feedback is considered in detail, and a transmission system for this latter case is given and analyzed. This system is shown to achieve a transmission rate very close to the largest rate possible.
    • Field Testing of Telemetry Systems

      Pickett, R. B.; Vandenberg Air Force Base (International Foundation for Telemetering, 1970-10)
      Tests have been developed and implemented at the Western Test Range for calibration of telemetry receiving systems. The tests serve an additional function as diagnostic aids.
    • FM Distortion Caused by Head-to-Tape Spacing

      Hodder, W. K.; Monson, J. E.; Bell & Howell Research Labs; Harvey Mudd College (International Foundation for Telemetering, 1970-10)
      Although it is well-known that frequency-modulated waves are distorted by systems with non-uniform frequency response, this distortion is difficult to calculate for most systems. The nature of the head-to-tape spacing transfer function allows the development of a closed form solution for FM distortion. Three methods of processing the voltage off the playback head are considered. Integrating the voltage results in amplitude-frequency distortion, but no harmonic distortion. Taking the voltage either directly off the head or differentiating it give both amplitude-frequency distortion and harmonic distortion. Experiments have verified the theoretical results.
    • Format and Address Equation Generation by Computer

      Leighou, R. O.; Hill, K. H.; Martin Marietta Corporation (International Foundation for Telemetering, 1970-10)
      Addressable remote multiplexed time division telemetry systems are being used more and more. Most of these systems operate with serial addresses generated by a central unit where each data source has a unique address. Thus the address sequence determines the particular format. In one type of system, the address sequence is determined by transfer logic between a counter and an address shift register. It takes several man-weeks of effort to develop a format and the logic equations to implement the address sequence for that format. To avoid this effort, an algorithm and computer program that generates the formats and the logic equations has been developed and is described. The program data inputs are: the basic format configuration of addresses (channels or data sources) per frame and the frames per master frame; and the number and types of channels at each samples per master frame (S/MF) rate. The program outputs are: address assignments by program ID, telemetry formats sequences with program ID, and the set equations for the address output shift register. Several checks are made during the program and if program restrictions are violated or format generation is impossible, error messages are printed and the program may be halted.
    • The Implmentation and Utilization of DSB/FM Telemetry Systems

      Johnson, C. S.; Sandia Laboratories (International Foundation for Telemetering, 1970-10)
      Two different double sideband suppressed subcarrier telemetry systems have evolved in the past few years: the harmonic subcarrier method (HSM) and the independent subcarrier method (ISM). This paper provides information pertinent to the implementation and utilization of both systems. The important features of the two systems are discussed by comparing the circuits used in their implementation. Test data is used to illustrate some of the important points about the performance of a DSB/FM telemetry system.
    • Instrumentation Systems Engineering Management

      Warren, J. R.; Norton Air Force Base (International Foundation for Telemetering, 1970-10)
      Examples of practical, effective, tools for the management of systems engineering have been presented. The usage of those tools is further examined. Management, as used here, pertains to the technical management of the systems engineering Job. The techniques described are structured around a medium/large data transmission/ acquisition/processing system. The principles can be applied to other systems also. Fundamental to the discussion is the use of models, criteria, and selected data for evaluation which results in decisions and program direction for systems optimization.
    • International Telemetering Conference Proceedings, Volume 06 (1970)

      International Foundation for Telemetering, 1970-10
    • L- and S-Band Antenna Calibration Using Cass. A or Cyg. A

      Taylor, Ralph E.; NASA Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      This paper describes a stellar calibration technique, using the absolute flux density from Cassiopeia A or Cygnus A, to determine effective antenna gain, or system noise temperature, at the IRIG L- and S-band frequencies. Paraboloidal dish antennas, ranging from 20 feet to 85 feet in diameter, can be calibrated using a total-power conventional RF receiver. Previous investigators utilized a Dicke radiometer to perform the same function. It is recommended that the Cass. A and Cyg. A flux densities, known within several tenths of a decibel, be utilized to calibrate IRIG antennas located on the North American Continent. It is demonstrated that Cass. A and Cyg. A provide sufficient signal power to calibrate a 20-foot diameter dish antenna; dish antennas up to 85-feet in diameter may be calibrated without applying a beam correction factor. Precision values of absolute flux density for Cass. A and Cyg. A are given for the 1700-1710 MHz space research, and IRIG 1435-1540 MHz and 2200-2300 MHz bands. An accurate radio sky map is also provided that may be scaled in frequency for the various bands.
    • A Long Term Remote Intragastric pH, Temperature, Motility and Electrical Activity Monitoring System

      Wise, Leslie; Jones, Paul W.; Womack, G. J.; Ballinger, Walter F.; Washington University School of Medicine; McDonnel Douglas Astronautics Company (International Foundation for Telemetering, 1970-10)
      The system under development can monitor intragastric physiological changes over time periods exceeding fourteen days. Prior to this development, long term intragastric measurements were impossible in freely mobile subjects. The electronic instrumentation includes a tethered sensor capsule, automatic titration unit, telemetry system, and data display. The system requires minimal maintenance during the prolonged monitoring period. The sensor capsule utilizes a pH sensitive glass electrode with wet reference, a thermistor, a solid state pressure sensitive transducer, and impedance matching electronics which develop the physically related electrical signals. Signal acquisition is via tether hardline to the multichannel telemetry unit and subsequent RF transmission to a central data receiving system for display and storage. Automatic titration functions, a myograph to record voluntary muscle movement, and the measurement of skin resistance as an indicator of stress, may also be included in the telemetry data. Capsule system tests in vitro indicate these accuracies: ± 0.2 pH units over a range of 1 to 10 pH; ± 0.2°C over a temperature range of 25°C to 45°C; and ± 10% over a pressure range of 0 to 15 inches of water. Life tests of the capsule in vitro show useful life times of the order of 30 days. Preliminary human in vivo experiments have confirmed the capsule sensitivity and stability.
    • The Lunar Communications Relay Unit System Design

      Trachtenberg, B.; RCA Corporation (International Foundation for Telemetering, 1970-10)
      Lunar Surface Exploration by Early Apollo Astronauts was limited by the range capabilities and configuration of the surface communications. To permit greater scientific yield from manned lunar exploration, it was necessary to provide improvements in crew mobility plus communications compatible with extended extravehicular activity. Expansion of EVA and video communications capability was constrained by the requirement of interfacing with existing earth and lunar surface facilities, vehicle payload requirements, and crew operational considerations. Various trade-off s were conducted to permit rapid development of a feasible communication's system which are described herein. The revision of the EVA mission profile necessitated establishment of new signal design parameters compatible with mobile and fixed site relay configurations. The design approach selected required strict discipline to enable integration of the electrical, mechanical, thermal and human factor fields. The resultant design of the Lunar Communications Relay Unit is a portable communications package to provide relay-to-earth of voice, data and color television from lunar surface locations far beyond the LM landing site and relay of ground voice to the EVA crew.
    • Machine-to-Machine Compatability in Wideband recording

      Levy, Avner; Ampex Corporation (International Foundation for Telemetering, 1970-10)
    • Manned Space Flight Network Telemetry System

      Underwood, Thomas C., Jr.; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      This paper discusses the Manned Space Flight Network (MSFN) Telemetry System as it has been developed through the Mercury, Gemini, and Apollo programs and is now being modified to meet Skylab, Earth Resources Technology Satellite (ERTS), and Apollo "J" mission (Apollo 16 and subsequent lunar missions) requirements. The existing telemetry system must be modified to meet the requirements of these future programs. This modification will consist of the implementation of automated configuration switching, centralized control of telemetry subsystems, tunable FM and PSK modulators/ demodulators, high frequency PCM signal conditioners, and the upgrading of both the wide band instrumentation magnetic tape recorders and the PCM decommutation capability. The resulting telemetry system, which will be capable of supporting various manned and unmanned space missions, is described here. Data flow diagrams are delineated and equipment electrical characteristics are discussed.
    • Manned Space Flight Network Unified S-Bond System 1970

      Spearing, R. E.; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
    • Micro Miniature Intraoral Telemetry System

      Scott, Ian S.; Ash, M. M.; University of Michigan (International Foundation for Telemetering, 1970-10)
      Intraoral telemetry is often-the only method of evaluating dental problems involving environmentally dependent relationships between occlusion, jaw movements, and the neuromuscular system, and between pH, Eh and bacterial ecology. To study these dental problems a small transmitter (the size of a molar tooth crown) with low power requirements and capable of monitoring eight physiologic parameters has been developed. Such transmitters are now being used to evaluate the design of dental bridges and related neuromuscular dysfunction.
    • A New Comcept for Equalization of Magnetic Tape Reproduce Systems

      Byers, Robert A.; Bell & Howell Company (International Foundation for Telemetering, 1970-10)
      A new approach to the problem of equalizing direct reproduce channels of instrumentation tape recorders has been developed. The technique employed utilizes active circuits and signal processing to develop the required transfer function. The principal advantage of the approach is that it requires only one operational adjustment to obtain the equalization characteristics. This allows a significant reduction in operator setup time and an increase in reliability by the reduction in the number of variable circuit elements. This is achieved by a slight increase in overall circuit complexity, the effect of which is minimized by the repetitive use of simple, functional circuits. The overall system approach is suitable for hybrid or monolithic technology.
    • Noiseless Linear Feedback and Analog Data Tranmission

      Butman, S.; California Institute of Technology (International Foundation for Telemetering, 1970-10)
      It is well known that noiseless linear feedback achieves channel capacity for the additive Gaussian channel. It has also been shown that it can be used to achieve the rate-distortion bound on the mean squared error for an arbitrary Gaussian source sent over the infinite bandwidth white Gaussian channel. However, it is shown here that noiseless linear feedback by itself does not suffice when the channel is bandlimited. It is shown that, out of the more than countable variety of Gaussian sources that ordinarily exist, only a countable subset can be transmitted via the bandlimited noiseless feedback link at the theoretical efficiency predicted by Shannon's rate-distortion bound. Thus, some nonlinear operations are necessary in almost all cases even with feedback.
    • Notch Noise Loading Data on Baseband Tape Recording

      Heideman, W. R.; Nichols, M. H.; Aerospace Corporation (International Foundation for Telemetering, 1970-10)
      Notch power ratio tests were performed on a magnetic tape recorder/ reproducer, using direct recording in the baseband. For the equipment tested, it is concluded that the IRIG method of setting the record power level as that which produces 1% third harmonic on a single tone, does not necessarily result in an optimum record/reproduce cycle. It is concluded that the input and output levels should be set with reference to notch noise test data to optimize baseband tape recording performance for baseband recording of frequency division multiplexed systems. In order to interpret the notch noise data, it was necessary to assume two non-linear processes, one acting in conjunction with the record process and one in conjunction with the playback process.
    • On Linear Information-Feedback Schemes for White Gaussian Channels

      Fang, Russell J. F.; COMSAT Laboratories (International Foundation for Telemetering, 1970-10)
      For the transmission of a Gaussian information source over an additive white Gaussian-noise (AWGN) channel, several noiseless, linear-feedback schemes are shown to be the same in the sense that they not only achieve the rate-distortion bound on the minimum attainable mean-square error (MSE), but also possess identical system parameters. These equivalent schemes can be easily applied to solving the problem of optimally matching a colored Gaussian source with an AWGN channel. These equivalent schemes can further be employed to send messages from digital information sources over AWGN channels. It can be shown that any of these equivalent schemes as a decision-error probability which is the smallest among the class of all linear schemes. The condition of noiseless feedback can be relaxed to cover the more general noisy information-feedback case. A suboptimal scheme is proposed for transmitting data from a Gaussian source, whose output process has a power spectral density function which is uniform in some frequency range and zero elsewhere, over some AWGN channels to some destination. This suboptimal noisy feedback scheme can also be used to send data from a digital information source over an AWGN channel with better performance than can be achieved without noisy feedback.
    • Optical Processing Interfaces

      Shulman, Arnold Roy; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      A brief introduction to coherent optical data, processing is given. Several problems are discussed concerning the implementation of coherent optical data processing for general use. The major problems discussed are concerned with the imaging qualities of coherent systems and the material requirements for recording these images. The solution to several problems is presented and the state-of-the-art in other areas is indicated.
    • PCM Processing in Bandpass Signals

      Shaver, F. H.; Aerospace Corporation (International Foundation for Telemetering, 1970-10)
      Several types of errors are generated when a bandpass analog signal is sampled such that it can be encoded into a sequence of digital words. Two of these types of errors are particularly dependent on the frequency band occupied by the input signal. These are: (1) the aliasing errors due to generation of unwanted spectral components and, (2) pulse width errors due to the use of finite width, flat topped pulses when regenerating-the analog signal. Expressions are presented for the spectral densities and total power of these error sources. The particular dependence of each on the location in frequency of the input signal is investigated and discussed. Quantization noise and distortion due to the smoothing filter which is used to reconstruct the signal are not considered in this paper. It is determined that the aliasing noise power as a function of the ratio of the signal center frequency to the sampling frequency has a series of relative minimums and maximums. A relationship defining the ratios at which the minimums occur is presented. An approximate formulation for the sample pulse width error is presented which allows a simple estimate of its magnitude to be made without knowledge of the smoothing filter transform or the sampling frequency. Quantitative results are presented as a function of the percentage bandwidth of the signal and the ratio of the sample pulse duration to the period of the center frequency of the signal. The results of the analyses are interpreted as design constraints.