• Quadrature Modulation Hybrid Voice and Data Modem

      Lerner, Theodore; Lerner Technology Inc. (International Foundation for Telemetering, 1977-10)
      The Quadrature Modulation Hybrid Modem is a new system designed to provide voice only, data only, or combined voice and data communication. It provides good voice intelligibility at low values of C/N0 by making use of a quadrature modulation technique which permits essentially nonthresholding demodulation of the voice signal. Power sharing between voice and data signals can be easily changed to accommodate different requirements. Intelligibility tests have been performed and indicate an intelligibility of 90% in the voice-only modem at a value of C/N₀ of 43 dB-Hz, and an intelligibility of 80% in the combined voice and data mode at a value of C/N₀ of 43 dB-Hz with an error rate for data of 10⁻⁵.
    • Results of a Q-M/PSK Data Modem Performing in a Hybrid, Voice and Data Mode, Through the ATS-6 Satellite

      Golab, Joseph; Duncombe, Christopher; Bland, Robert G.; U. S. Department of Transportation (International Foundation for Telemetering, 1977-10)
      The Transportation Systems Center (TSC), under the sponsorship of the FAA, has been involved in the development of advanced voice/data multiplexed modems applicable to ground-aircraft communications via satellite in support of the AEROSAT program. TSC was assisted by the Canadian Ministry of Transport (MOT), Communications Research Center (CRC), in the planning and conducting of recent flight test experiments using the NASA ATS-6 satellite.
    • Review of Microstrip Antenna Development at the Pacific Missile Test Center

      Kaloi, C.; Pacific Missile Test Center (International Foundation for Telemetering, 1977-10)
      Pacific Missile Test Center personnel have been conducting theoretical and experimental studies on microstrip antennas since 1965. A number of operational microstrip antenna systems have been developed. This report reviews development efforts at Pacific Missile Test Center on types of microstrip antenna elements used in these operational systems. Results of near field probing of different microstrip antenna elements are presented. These results are used as a basis to discuss microstrip antenna electrical characteristics such as orthogonal current oscillation, orthogonal charge oscillation, dipole moment of charge distribution oscillation, dipole moment of charge distribution rotation, far field radiation patterns, polarization, etc. Application of microstrip arraying techniques on thin flexible substrates that can be readily mounted conformally to the exterior surface of a missile without missile disassembly is discussed.
    • A Satellite Automatic Control System

      Bleiweis, J. J.; Redman, P. C.; COMSAT Laboratories (International Foundation for Telemetering, 1977-10)
      The primary task of existing satellite control centers is to automatically monitor the operational performance of existing satellites and to manually generate control commands so that these satellites remain within specified operational limits. This paper describes some basic characteristics of an existing satellite control center and identifies a method that may be employed to gradually introduce automatic commanding to the facility. Candidate methods of automatic commanding are described.
    • Self-Steering Arrays

      Kummer, W. H.; Hughes Aircraft Company (International Foundation for Telemetering, 1977-10)
      Self-steering arrays using complete receiver-transmitter-signal processing systems to direct the beam of an antenna automatically have been developed. These systems offer an alternative to mechanically gimballed systems for satellite communication applications. The operation of such systems using either a pilot signal or a phased lock loop technique for self-steering is described. Also described is an engineering model built for satellite-to-earth communications which incorporates these techniques. Additionally, other systems now in breadboard configurations are mentioned briefly. A summary of power requirements for a projected 25-module system has been included to indicate the feasibility of larger systems. Test results for the engineering model have proved satisfactory, and show that these systems can definitely be valuable in applications similar to the tracking and data relay satellite system (TDRSS) described here.
    • Sideband Lock SCPDM Modem for Simultaneous Voice and Data Communications

      Harris, Konstantine W.; Udalov, Sergei; Magnavox; Axiomatix (International Foundation for Telemetering, 1977-10)
      A modem technique for simultaneous transmission of voice and digital data is presented. The salient feature of this technique is the use of quadrature carrier multiplexing of a suppressed clock pulse duration modulation (SCPDM) signal with a biphase NRZ data stream. A novel method for separating the voice and data components at the receiver is described. Data bit error rate and voice intelligibility test results are presented and discussed.
    • Some Operational Considerations in Deploying Anti-Jam Communications

      Goldman, Herbert B.; Hughes Aircraft Company (International Foundation for Telemetering, 1977-10)
      Operational and deployment considerations are described to enhance the performance of jam resistant communications. The potential different ground propagation characteristics of spread spectrum and CW type waveforms are used to the advantage of the communication system. Emphasis is placed on the use of tactical relay to continuously optimize against the jammer. Tactics such as spoofing are described as a technique in confusing the intelligent jammer. The objective of this paper is to illustrate how anti-jam communications with nominal AJ performance improvement can effectively be employed in a ground environment. These include the brute force and the so-called intelligent or sophisticated jammer. For many years the utilization of anti-jam communications has been stifled in anticipation or the optimum solution against the optimum jammer. When evaluating a "one on one" scenario where the jammer is dedicated to jamming a specific link there is an unending subset of tradeoffs of optimum techniques to consider. However, when the jammer is trying to disrupt communications along a broad geographical axes. the techniques of jamming and communicating should be based on more general operating conditions. The ground communications environment in the presence of ground-based jamming presents the greatest opportunity for improving performance as a function of propagation anomalies and the use of relay. Airborne terminals within line of sight of the jammer have the most severe jamming environment. Ground based terminals generally will have an advantage of terrain against the ground based jammer. Those links that exhibit poor communications margin should always have the option of an alternate route in a jamming environment. The alternative to an alternate route is to provide excessive performance margins for worst case analysis. Unfortunately there is a significant cost factor associated with this latter approach. An important element of the scenario is the concept of position location. The use of position location and reporting equipment enables the apriori determination of appropriate links by different classes of users. As an example an aircraft can maneuver close to a ground terminal for communications to utilize the advantage of range ratio. This can be done in the worst case of a close Air Support Mission where the FO must provide voice or digital data to direct a strike at several mobile targets. At high altitudes the AC may be jammed but at low altitude the link may be viable. At low altitudes the aircraft A-G link will be constrained to a small geographic area and must therefore know which area to cover. The use of GPS can also be enhanced at low altitudes against the ground based jammer if acquisition of the GPS signal can be speeded up. The use of a digital matched filter (DMF) for CA code acquisition can provide this capability.
    • Telecommunication Applications for CTD Devices

      Gopen, C. W.; Reticon Corporation (International Foundation for Telemetering, 1977-10)
      A relatively new type of component, the CTD (Charge Transfer Device) is now available to the commercial market. After five years in the development lab, these parts are finding their way into many applications including telecommunications. This paper will give a brief overview of the device theory and discuss three particular devices: 1) a transversal filter, 2) a Binary Analog Correlator, and 3) chirped transversal filter used to implement a Discrete Fourier Transform.
    • Telemetry Antennas for Deep Space Probes

      Brejcha, Albert G.; Smith, Charles A.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1977-10)
      The requirement for real time imaging telemetry and the continued increase in science payloads on deep space missions have played a major role in the evolution of deep space probe telemetry antennas. This paper describes the high data rate telemetry antennas that were flown on the Mariner Mars 1969 and 1971, the Mariner Venus Mercury 1973, the Viking 1975 and the Voyager spacecrafts. Performance parameters are reviewed and general design concepts are described. The Mariner Mars 1969 and 1971 antennas were single frequency (S-band), one meter diameter antennas. The Mariner Venus Mercury 1973, Viking 1975 and Voyager antennas were dual frequency (S and X-band), with diameters of 1.4 meters, 1.5 meters and 3.7 meters respectively.
    • A Test System for a Miniature Neutron Detector

      Balls, Jerry D.; Bowers, John L.; The Bendix Corporation (International Foundation for Telemetering, 1977-10)
      A flexible automated test system for calibrating and testing a miniature neutron detector, used in telemetry systems, is described. The test system is cost effective, easily calibrated and maintained, and was available for use 6 months after design initiation.
    • Tethered Balloon for Checkout of Computer-Controlled Antennas

      Baggot, H. E.; Wynn, J. B.; Interstate Electronics Corporation; Department of the Navy (International Foundation for Telemetering, 1977-10)
      During operational tests of the U.S. Navy's Poseidon missile, an instrumented ship tracks every test missile launched by the nuclear subs. The key sensor aboard this launch-area support ship, the USNS RANGE SENTINEL, is its antenna system. Onboard computers switch the ship's four independent, main S-band antennas (Fig. 1) to capture up to four missiles fired in succession and to expedite command action (e.g., continued flight or destruct). This multi-antenna control by computer leads to a complex testing problem for the computer software, constrained by the need for cost effectively proving the software's operational capability without penalizing hardware development. Rigid control of hardware-caused variables, and a near-operational test environment, are vital Software test prerequisites. To this end, using a stable RF pointing source at altitude above the antennas (i.e., to reduce parallax distortion and multipath effects) is a preferred approach in testing antenna-management software. This paper describes two experiments* to (1) initially establish the feasibility of using an airborne S-band telemetry transmitter as an RF signal source for checking out the USNS RANGE SENTINEL's antenna control, and then (2) demonstrate the effectiveness of this RF source in verifying the ship's antenna alignment and validating the operational antenna software.
    • Understanding & Specifying Hi-Density Digital Recording Systems

      Schulze, Glen H.; Bell & Howell (International Foundation for Telemetering, 1977-10)
      Rapid advancement of hi-density digital recording technology has left most user organizations in a confused and bewildered state with respect to understanding and, more importantly, specifying hi-density recording systems. Users attempting to acquire advanced hi-density hardware either without procurement specifications or with incomplete or shallow specifications will probably gain the needed experience too late, after an unusable system has been delivered. Several prominent user facilities have recently bought and accepted hi-density recording hardware and immediately been forced to retire the equipment from use to avoid disastrous embarrassment. Other users have had to redesign accepted equipment before it could be used. One user who blindly accepted a proposal to convert several newly ordered analog recorders to a digital format had to remove and dispose of the digital electronics after delivery and revert back to analog methods. The ability to professionally specify and technically monitor a hi-density recording system contract can only be based upon a thorough understanding of the high density digital coding, recording, reproducing and decoding process. The purpose of this paper is to identify and discuss the more important elements of this emerging technology for users who suddenly find themselves needing this capability.
    • Underwater Optical Beam Tracking

      Gagliardi, R. M.; University of Southern California (International Foundation for Telemetering, 1977-10)
      The use of blue-green laser frequencies for establishing an air ocean underwater communication channel has been well accepted. However any attempt to initialize or maintain such a link will invariably require some method of accurately spatially pointing and tracking the penetrating beam. In this paper we present results of a study concerned with determining the ability to spatially track an optical after undergoing underwater propagation. By invoking the concept of modulation transfer theory and substituting established propagation models for underwater coherence functions, the focal plane intensity patterns generated in wide angle optical lensing systems can be determined, as a function of the link characteristics (e.g. sea state, depth into the ocean, turbulence, etc.).With the intensity pattern modeled, the behavior of various forms of optical trackers can be analyzed by the application of standard tracking loop theory. Of particular interest here is the application of well known mathematical tools, such as Kolmogorov theory, which allows generalized statistical analysis to be performed on both linear and nonlinear dynamical systems. The result of such an approach is the development of a differential equation whose solution yields the statistics of the tracking error. Theoretical studies of this type have been examined previously for generalized scattered optical fields [1]. With these basic approaches as a guide, mean squared tracking errors can be derived, which assesses the perfomance of the beam tracker in relation to the channel characteristics.
    • VHF Adaptive Array Test Results

      Zeger, Andrew E.; Burgess, Lawrence R.; General Atronics Corp. (International Foundation for Telemetering, 1977-10)
      A four-element Anti-Jam Antenna Array (AJAA) system has been built to provide protection for U.S. Marine Corps inter-command post communications in the 30-76 MHz band. A unique and important feature of the AJAA system is its ability to spatially null jammers down to a level below that of the desired signal. This capability and the prevention of accidental cancellation of the desired signal is achieved by using the desired signal's direction-of-arrival (DOA) in a prebeamformer located ahead of the adaptive beamformer. A positive S/J at the array output is required to prevent capture by a co-channel interference in standard FM field radios. Antenna range tests were performed on the AJAA system using AN/PRC-77 radios as far-field signal and jamming sources. Results of these tests show that the AJAA provides an intelligible FM voice signal at its output while simultaneously suppressing three jammers.