• Double Quadriphase Modulation/Demodulation Technique for Three-Channel Communication Link

      Alem, Waddah K.; Axiomatic (International Foundation for Telemetering, 1977-10)
      A modulation technique for a three-channel communication link is introduced. The structure of the modulator is such as to form an unbalanced quadriphase signal wherein the high rate data stream is bi-phase modulated on the in-phase carrier component, while the sum of the two lower rate signals is bi-phase modulated on the quadrature component of the same carrier. The sum of the two lower signals is, in turn, formed by modulating with the respective data streams the in-phase and the quadrature components of a square wave subcarrier. At the demodulator, the tracking of the carrier and the subcarrier is performed by two independent Costas loops. The demodulation of the high data rate signal is carried out after establishing the carrier reference signal, while the lower rate signals are demodulated after the subcarrier loop recovers the subcarrier. In this paper, the performance of the two loops is analyzed and the expressions for the tracking errors are derived. Finally, a numerical example pertaining to the Space Shuttle-to-TDRS Ku-band link is presented for illustration.
    • ECM/ECCM Effects on Voice Transmissions

      Buskirk, Ronald L.; Nossen, Edward J.; Government Communications Systems (International Foundation for Telemetering, 1977-10)
      An evaluation methodology for conventional and ECCM voice communications is presented, wherein intelligibility of the received message rather than error rate or signal-to-noise ratio is the quantity measured. This allows the engineer to include the psychoacoustic phenomena of a human listener in his system design considerations. Analyses have been performed which allow transformation of speech articulation test results into data more meaningful to the communications engineer. Since message intelligibility is established after baseband reconstruction of the voice signal, this method is universally applicable to most voice transmissions. It is insensitive to the nature of the medium, modulation, and interference sources. Examples are presented showing applications of these guidelines to the design of frequency hopping radios. Tests run on a simulator confirm the analyses. A sample tape is available to demonstrate some of the effects.
    • EDP Tape - Performance and Reliability - Past, Present and Future

      Fiori, J. J.; General Services Administration (International Foundation for Telemetering, 1977-10)
      This report was prepared by the Electronics Division, Federal Supply Service of the General Services Administration and is intended to share with all interested parties, the information and experiences with EDP Computer Tape gathered by the GSA since 1966, when it assumed the responsibility to support procurement of these items for all Federal agencies. It is hoped that the information contained herein will be of benefit to the tape-using community and will lead to a better understanding of the Government's role in providing high quality computer tape to meet current and future data storage applications. The General Services Administration's active involvement in the program to supply high quality computer tape to Government agencies was initiated through the development of Interim Federal Specification W-T-0051. The specification was based upon technical requirements received from the tape-using community and inputs supplied by the tape industry. GSA Laboratory facilities are utilized for product qualification testing, specification development testing and quality assurance testing. It is from all of these sources that the data presented herein was gathered. To establish some kind of perspective, it should be noted that these results are representative of the over 25,000 reels of computer tape sampled, tested and evaluated annually by GSA in support of annual procurement volumes of approximately 1 million reels. In addition to presenting quantitative data showing how tape quality levels have increased over the past four years, the report also addresses past problems and recent improvements, and further attempts to identify those remaining areas in which the tape industry must concentrate its future developments.
    • Encoding of Telemetry Data in a Standard Video Channel

      Rieger, James L.; Naval Weapons Center (International Foundation for Telemetering, 1977-10)
      Various methods for compressing of a television image to fit a channel of reduced bandwidth are available; most are difficult and/or expensive to use, and many degrade the resulting picture appreciably. This paper describes an alternative method of placing the signals which accompany the picture within the passband of a picture, and separating them again at the receiving end with minimum crosstalk and picture degradation.
    • Experimental Comparison of Pulse Code Modulation Codes for Magnetic Recording

      Law, E. L.; Pacific Missile Test Center (International Foundation for Telemetering, 1977-10)
      The bit error probability (BEP) versus signal-to-noise ratio (SNR) was experimentally determined for Non-Return-to-Zero-Level (NRZ-L), Bi-Phase-Level (BIΦ/-L), Delay Modulation (DM) and Miller Squared (M²) codes for a bandpass channel. This was done by passing the data through a 400 Hz to 500 kHz Bessel bandpass filter and linearly adding noise. The power spectral density of the noise was shaped to match the noise out of an analog magnetic tape recorder running at 30 inches per second (in./s). This provided a simulation of an optimum wideband 2.0 MHz tape recorder running at 30 in./s (no flutter, tape dropouts, etc.). The bit rate, pattern, and code to be tested were then selected. The SNR was varied until the bit error probability was approximately 10⁻⁶ With a commercial Pulse Code Modulation (PCM) bit synchronizer with a "good" dc restorer and a pseudo-random pattern at 1.0 megabits per second (Mb/s) (33.3 kilobits per inch (kb/in.) equivalent packing density), NRZ-L had a 4 dB SNR advantage over DM and a 14 dB advantage over BIΦ/-L for a BEP of 10⁻⁶ through the bandpass channel. At 1.5 Mb/s, NRZL had a 6 dB advantage over DM and a 10⁻⁶ BEP was not achievable with BIΦ/-L coding. For a synchronizer with no dc restoration NRZ-L had only a 1 dB advantage over DM at 1.0 Mb/s and also only a 1 dB advantage at 1.5 Mb/s. M² gave the same results as DM for pseudo-random data. However, M² was relatively insensitive to patterns while DM and NRZ-L required a higher SNR with a "good" dc restorer and lost synchronization completely with no dc restorer for worst case 16-bit repeating patterns.
    • Fiber Optical System Performance with Avalanche Gain Detection

      Sorensen, Alfred N.; California State University (International Foundation for Telemetering, 1977-10)
      The purpose of this paper is to consider optical system performance for selected digital signal formats when shot noise limited avalanche photodetection is implemented. Performance characteristics for binary on-off keyed (OOK) and pulse position modulation (PPM) are given, in addition to M-ary PPM and PAM.
    • A Frequency Modulated S-Band Telemetry Transmitter

      Homa, M. L.; Ward, J. H., Jr.; E-Systems (International Foundation for Telemetering, 1977-10)
      The need to efficiently collect data from remote locations has resulted in the widespread use of radio frequency telemetry. This paper addresses the requirements, considerations, and implementation of such a system. Since many components of a telemetry link are subjected to harsh operating environments, considerations of system constraints imposed on the transmitter by these conditions will be presented. Several design approaches of an S-Band frequency modulated telemetry transmitter will be offered, and tradeoffs associated with each discussed. Having selected the most desirable transmitter design approach a pictorial display of the hardware used to fulfill the requirements will be presented along with measured performance data. The key circuits discussed will be an S-Band VCO, parametric divider, buffer/power amplifier, and stabilizer/modulator. The RF circuits employ microwave integrated circuit construction while the stabilizer/modulator utilizes thin and thick film hybrid technology. Extensive use was made of computer analysis resulting in uniformly producible circuits that provide good correlation between measured and specified performance. This helped to produce a 25% reduction in production cost over the previous discrete component design of 1969 vintage. Basic circuit design lends itself well to special mechanical configurations, as well as flexibility in modulation formats and RF power output levels. By using the computer aided design approach, five percent RF bandwidths were realized which would enable the transmitter to be frequency agile for secure or multivehicle telemetry.
    • A High Data Rate Recorder/Reproducer

      Brobst, R. E.; Odetics, Inc. (International Foundation for Telemetering, 1977-10)
      A High Data Rate Recorder (HDRR) has been developed under contract with Engins Matra, France, to be used in the European Spacelab. Engins Matra is responsible for the design and testing of the Command and Data Management System (CDMS). The HDRR is part of the CDMS which performs on-board data processing, multiplexing and storage. The Spacelab is a primary payload of the U. S. Space Shuttle Orbiter. The HDRR interfaces with the Spacelab High Rate Multiplexer, which, in turn, provides the inputs to the Tracking Data Relay Satellite (TDRS) down-link system for transmission to the ground. The HDRR is capable of recording and reproducing at a maximum rate of 32 Mb/s. The total continuous record time allowed at this rate is 20 minutes. Thus a total of 3.84 x 10¹⁰ bits can be stored. The HDRR has a versatile command and data interface that allows for recording at any rate between 1 Mb/s and 32 Mb/s. Reproduction can be performed at 2 Mb/s, 4 Mb/s, and any rate between 8 and 32 Mb/s.
    • Impact of Intelligent Systems on the Telecommunication Interface

      Chien, R. T. (International Foundation for Telemetering, 1977-10)
      In the next ten years, there will be a great deal of development in the area of theory and applications of intelligent systems. Some of these systems will be related to industrial automation in manufacturing and some others will be related to automation in the cockpit of aircrafts. In this paper, a major project in computer aided decision-making (CADM) will be examined in detail. This CADM System serves as a potential co-pilot for flight operations and proposed to handle many of the routine duties of the pilot. It assists the pilot in data-processing, signal detection, flight planning, navigation, obstacle avoidance, and interaction with ground and air communicators. The purpose of this paper is to examine the new environment and the impact it has in telecommunication needs in the direction of future research and development. A movie will be shown of the project demonstrations.
    • An Integrated Error Correcting/Pseudo Random Communication System

      Schiff, Maurice L.; ITT Aerospace Optical Division (International Foundation for Telemetering, 1977-10)
      This paper describes a pseudo random (PN) communication system with an integral error correcting code. The error codes are again based on maximal length sequences and simultaneously provide coding gain with bandwidth expansion. A basic modem starting at 2400 bps data rate and expanded to a 5 Mbps chip rate is described. Theoretical and hardware test results are presented to verify the concepts. Finally, synchronization of this system is discussed. A PN range extension concept is developed which improves the acquisition time with only a trivial increase in system complexity.
    • International Telemetering Conference Proceedings, Volume 13 (1977)

      International Foundation for Telemetering, 1977-10
    • JTIDS Modular Design to Use SAW Devices

      Grasse, Charles L.; Teledyne MEC (International Foundation for Telemetering, 1977-10)
      The Joint Tactical Information Distribution System (JTIDS) concept is designed to integrate the military's needs for communication, navigation and identification equipments into a cost-effective avionic suite. A key element to be used in achieving these goals is the surface acoustic wave (SAW) bandpass filter...in the form of a bandwidth selectable module. In order to satisfy the JTIDS requirements of today, as well as the Tactical Information Exchange Systems (TIES) of the future, it is necessary to utilize state-of-the-art SAW resonator/filter designs ... in conjunction with more conventional SAW bandpass filter technology. It is this approach that will make possible the quality performance required in a small, low cost module.
    • Modeling of Optical Propagation in the Underwater Environment

      Karp, Cherman; Naval Ocean Systems Center (International Foundation for Telemetering, 1977-10)
    • MSK Modulation for Multiple Access

      Magill, E. G.; Fairchild Camera and Instrument Corporation (International Foundation for Telemetering, 1977-10)
      Minimum Shift Key (MSK) is known to possess desirable qualities, such as low spectral sidelobes and dual channels quadrature in both phase and sampling time. It is also a robust signal, tolerant to considerable amplitude limiting and spectral filtering. MSK modulation of Pseudo Noise (PN) sequences can be used to effect a communication network with multiple access, which can be of either random or assigned synchronism. Such a network exhibits resistance to jamming by external signals in the form of processing gain. This approach leads to multiple access terminal designs which are coherent, with a single RF front end which is not phase locked. A particularly effective implementation outlined in this paper utilizes a Charge Coupled Device (CCD) filter matched to the PN sequence as the basic correlating device for multiple access.
    • Multiple Access Methods in Commercial Communications Systems

      Dixon, R. C.; Spectrack Systems Inc. (International Foundation for Telemetering, 1977-10)
      Time division and/or code division multiple access techniques based on spread spectrum modulation and demodulation technology have found wide application in military systems. These techniques also offer advantages for use in systems that allow for large numbers of users in civil communications systems. This paper considers spread spectrum multiplexing as a technique that allows time division multiplexing multiple access to communications networks. It also provides for multiple networks to operate in the same band through code division multiplexing.
    • NASA Standard 4 x 10⁹ Bit Spacecraft Tape Recorder

      Welch, James P.; Odetics, Inc. (International Foundation for Telemetering, 1977-10)
      The concept of employing standard spaceborne hardware to meet the needs of present and future spaceborne missions is the beginning of a new era. In this paper, attention is focused on describing the functional characteristics of a 4 x 10⁹ bit magnetic tape recorder that will become the standard tape recorder for future satellite missions. The recorder development was directed by NASA Goddard Space Flight Center.
    • NASA Standard Communications and Data Handling Subsystem

      Robinson, Daniel L. (International Foundation for Telemetering, 1977-10)
      At the 1975 International Telemetering Conference Charles F. Trevathan discussed the Multimission Modular Spacecraft (MMS) in general and the Communications and Data Handling (C&DH) subsystem in particular. The National Aeronautics and Space Administration's Goddard Space Flight Center (NASA GSFC) Is managing the MMS program and is integrating the first spacecraft, the Solar Maximum Mission, in-house. Contracts have been let for the Modular Power Subsystem (MPS), Attitude Control Subsystem (ACS) and the Communications and Data Handling (C&DH) Subsystem. The C&DH subsystem provides the command and telemetry link between the spacecraft and the terrestrial system; distributes commands to and collects telemetry from all spacecraft systems via a duplex serial multiplex data bus and Remote Interface Units (RIU's); and contains on board computation capability. The C&DH is a single 4 x 4 x 1- 1/2 foot module. The staffed module weighs 270 pounds including 60 pounds of mission unique equipment. The future for this kind of versatile hardware is exceptionally bright as it is cost effective and its modular structure permits repair, refurbishment and even modification/dating in space.
    • NASA Teleconferencing Pilot Project (An Evaluation of Teleconferencing as a Substitute for Travel)

      Fordyce, Samuel W.; NASA (International Foundation for Telemetering, 1977-10)
      NASA conducted a Pilot Project during 1975 and 1976 to determine the extent that teleconferencing could replace travel to meetings. The network consists of approximately 34 teleconference rooms and 50 fast facsimile machines, all interconnected on private lines to a master switchboard in Huntsville, Alabama. In addition, portable conference telephones augmented the voice network, and experimental video teleconferences were tried. Evaluations show that the teleconferences "saved" travel costs approximating 21% of the travel budget at a communications cost of 3% of this budget. The unused travel funds were diverted into travel other than to management meetings, and consequently, coordination may have improved. This paper discusses the operation of the Pilot Project, which has matured into an operational teleconference network. This experience may be of value to other organizations wishing to adopt teleconferencing.
    • New Types of Flush-Mounted Telemetry Antennas

      Sindoris, Arthur R.; Jones, Howard S., Jr.; Reggia, Frank; Department of Army (International Foundation for Telemetering, 1977-10)
      Over the past few years new and unique types of cavity-backed, slot antennas have been developed that mount flush to the surface of a missile. These antennas have been designed and built to operate in the 300 MHz to 3 GHz frequency range and to produce low-gain (typically isotropic) wide-angle coverage with moderate radiation efficiency. As well as insuring good electrical performance, the basic design employs a copper-clad, dielectric-loaded cavity into which the radiating slot is machined or etched. This construction technique provides four important advantages: (1) The almost arbitrary shape or form factor of the cavity allows flush mounting to the surface of the missile or sandwiching between internal components with only the radiating slot exposed to the exterior of the missile. (2) Fabrication is simple. (3) Cost is low. (4) Mechanical strength is high. The cavity backing the slot is filled with a moderately high, dielectric constant material (such as a silicone, Teflon, or epoxy fiberglass) with a relative permittivity in the 2.5 to 4.5 range to decrease the size of the cavity and to provide mechanical strength to the antenna. The RF connection to the cavity is made by an inductive post and a coaxial connector. A 50 ohm input impedance is obtained over frequency bandwidths of 3 to 10 percent. By connecting two or more of these slot antennas together in a prescribed phase and amplitude relation, the direction of the radiation pattern can be controlled. Sidelooking or forward-looking patterns are possible by simple changes in feed network cable connections. The easy tunability of one of these new types of antennas allows application over greater than a 2:1 frequency range without any change in antenna dimensions.
    • Omnidirectional Telemetry Antennas

      Munson, Robert E.; Ball Brothers Research Corporation (International Foundation for Telemetering, 1977-10)
      Missiles, rockets, and satellites need as much uniform gain as possible to provide continuous telemetry coverage. The theoretical limit of an ideal antenna would be 0 dB gain with 100 percent coverage of 4π steradians. It is not practical to attain the theoretical limit in practice on missiles, rockets, and satellites. This paper describes how closely the theoretical limit can be approached.