• An Efficient Multichannel FFT Demodulator

      von der Embse, U. A.; Austin, M. C.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      A multichannel binary FSK demodulator for spaceborne application has been implemented using an efficient preweighted and thinned fast Fourier transform (FFT) algorithm. Theory, configuration, and performance are described and compared with the analog unit which performs the same functions. Being able to perform the first base 16 pass with add-only operations following preweighting, provided the complexity reduction which made it feasible to use the FFT to perform the channelization and predetection filtering.
    • End-To-End Information System Design at the NASA Jet Propulsion Laboratory

      Hooke, Adrian J.; NASA Jet Propulsion Laboratory (International Foundation for Telemetering, 1978-11)
      Recognizing a pressing need of the 1980's to optimize the two-way flow of information between a ground-based user and a remote space-based sensor, an end-to-end approach to the design of information systems has been adopted at the Jet Propulsion Laboratory. The objectives of this effort are to ensure that all flight projects adequately cope with information flow problems at an early stage of system design, and that cost-effective, multimission capabilities are developed when capital investments are made in supporting elements. This paper reviews the End-to-End Information System (EEIS) activity at the Laboratory, and notes the ties to the NASA End-to-End Data System program.
    • Engineering of a Multifunction Spread Spectrum System

      Winterkorn, John H.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      In the past ten years there have been dramatic strides in the spread spectrum communications system area. The knowledge of spread spectrum systems has progressed from a fragmented understanding of the techniques and their characteristics to the point where spread spectrum communication techniques are well documented and their characteristics are well understood. Thus, spread spectrum has progressed from analytical investigation into practical application. This presentation will provide a brief tutorial on spread spectrum techniques in the RF, modulation detection, and coding areas. The characteristics of these techniques will be addressed and related to specific communication functions. The presentation will address the application of spread spectrum techniques to a communication system design and will emphasize the suitability of spread spectrum for multiple applications in a given system. Specific examples of multiple spread spectrum usage will be given and a generalized approach to spread spectrum engineering will be presented. The application of this system approach to spread spectrum engineering results in spread spectrum taking on functions beyond its primary purpose of existence and becoming an integral part of a communication system rather than being an add-on, necessary but undesirable, appendage.
    • Experimental 2 GBPS MM Wave System and 4 GBPS QASK Modulator

      Horwood, D. F.; Luke, R. T.; Lee, G. E.; Des Brisay, G. S., Jr.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      A 2 GBPS QPSK modulator and demodulator were developed and BER performance was evaluated over a millimeter wave data channel. The error rate measurements taken with the breadboard equipment showed system performance to be less than 2 dB from theoretical at an error rate of 10⁻⁵. Additionally, a second QPSK modulator was constructed and combined with the first to generate 4 GBPS QASK data for future evaluation.
    • Experimental Evaluation of MSK and Offset Keyed QPSK Through Satellite Channels

      Horwood, D. F.; Angello, P. S.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      Laboratory test measurements show nearly equivalent error rate performance of MSK and OKQPSK modulation formats for channels having bandwidths approximately equal to the bit rate bandwidth and typical associated phase delay characteristics. High quality MSK and OKQPSK transmitters and a versatile modular receiver have been designed and constructed to eliminate differences associated with varying degrees of hardware quality when the performance of the various modulation formats is compared. The selection of a modulation format should, therefore, be strongly directed by considerations other than error rate, such as complexity, sensitivity to alignment, and compatibility with differential coding.
    • A Fast Complex Integer Convolution Using a Hybrid Transform

      Reed, I. S.; Truong, T. K.; University of Southern California; California Institute of Technology (International Foundation for Telemetering, 1978-11)
      In this paper it is shown that the cyclic convolution of complex values can be performed by a hybrid transform. This transform is a combination of a Winograd transform, and a fast complex integer transform developed previously by the authors. This new hybrid algorithm requires fewer multiplications than any previously known algorithm.
    • Fast Fourier Transform Algorithm Formulation

      Thong, Tran; General Electric Company (International Foundation for Telemetering, 1978-11)
      A new unified formulation of the fast Fourier transform based on the unwrapping of a multi-dimensional array is presented. The decimation in time FFT algorithms is treated in detail. The decimation in frequency algorithms is then discussed.
    • FET Amplifiers for Communications Applications

      Kennedy, W. Keith, Jr.; Watkins-Johnson Company (International Foundation for Telemetering, 1978-11)
      The Field Effect Transistor (FET) is revolutionizing microwave communications with both its low noise performance and high dynamic range. This paper emphasizes developed amplifier hardware available today for both ground and satellite applications. The focus is on the noise figures and output powers available from 4 to 15 GHz.
    • Fiber Optic Sensors for Military, Industrial and Commercial Applications

      James, K. A.; Quick, W. H.; Strahan, V. H.; Rockwell International Corporation (International Foundation for Telemetering, 1978-11)
      This paper presents concepts for fiber optic sensors. Such sensors have many inherent advantages over conventional sensors - including digital format and noise immunity. Four examples of specific sensor system designs are discussed - each of which demonstrates a different optical modulation format. The birefringent temperature transducer illustrates direct digital signal modulation. The temperature/pressure dependent semiconductor filter illustrates high-pass optical wavelength signal encoding, while the coupled polarized-mode transducer shows how a solid-state sensor can produce narrow-bandpass optical-wavelength signal encoding. Finally, the luminescent temperature sensor illustrates a manner in which a solid-state sensor can be constructed to produce pulse-width modulation of an optical signal. The potential for fiber-optics sensors adds one more facet to the growing fiber optics market.
    • A Flexible User Oriented Approach to Communications Systems Simulation

      Fashano, M.; Austin, M. C.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      An advanced software/hardware computer system developed for the simulation of communications systems is described. This user oriented system allows for flexible and efficient modeling and simulation of complex communications systems. Excellent agreement between simulation and measured results has consistently valididated the simulation approach.
    • Future Automated Spacecraft as an End-to-End System Element

      Bird, Thomas H.; NASA - Jet Propulsion Laboratory (International Foundation for Telemetering, 1978-11)
      Concepts for a highly automated spacecraft, which is much more independent of ground operations than current spacecraft, have been investigated. Applicable systems and technology requirements are identified for maximum onboard automation of mission functions. A spacecraft concept which requires infrequent ground contact while increasing mission effectiveness is described. The potential impact of such a system on end-to-end system design is discussed.
    • GDSC Aerospace Test System (ATS)

      Layton, J.; Schiano, C.; Grumman Data Systems Corp. (International Foundation for Telemetering, 1978-11)
      Grumman Data Systems Corporation (GDSC) is presently developing another in a series of computerized realtime systems which accepts, preprocesses, analyzes and displays telemetry and range data. This new Aerospace Test System (ATS) will first be utilized by the Navy at the Pacific Missile Test Center (PMTC). The computerized test system will analyze data, in realtime, being telemetered from missiles, aircrafts and satellities. The system will accept, decommutate/demodulate, preprocess, analyze and display data being transmitted in the forms of PCM, PDM, PAM, and FM. The system will allow test personnel to continually monitor, in realtime, critical raw and calculated parameters. The answers provided to test personnel, in one phase of the mission, will give them the ability to proceed into the next with a high degree of confidence. The vast amounts of data acceptable by the system, together with its analytical and display capabilities will allow test personnel to accomplish several tests during a single time frame. The system will also allow test personnel to be in complete control of their mission via the data uplink capability. It is a system that support Batch, Time Share, and Remote job entry processing concurrently. Utilized properly, it can greatly reduce the quantity and increase the quality of batch processing.
    • Genesis and Design of the Tracking, Telemetry, and Command System for the Navstar Global Positioning System

      Hoff, Charles S.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      The genesis and design of a unique Tracking, Telemetry, and Command (TT&C) System for the Navstar Global Positioning System (GPS) is described from the perspective of the System Architect/Engineer. Working from the diverse and sometimes conflicting mission requirements, derivative performance requirements for the TT&C System were generated. System design tradeoffs were performed in an effort to compromise conflicting requirements which affected the frequency domain, link budgets, antenna sizing, and modulation schemes. The characteristics of the resulting TT&C System included the following: a. Primary uplinking to the satellite on a spread spectrum secure link at X-Band. b. Use of a closed-loop uplink which takes advantage of existing onboard functions as references to achieve precise ground-space synchronization. c. Incorporation of state-of-the-art error control techniques to achieve high net data throughputs with concurrently "zero error" data transfer from ground to space. d. Hybrid frequency ground antennas to accommodate both the primary and backup command links, with compatible telemetry downlinks. A common S-Band frequency input within the satellite to both the primary wideband Pseudo Random Noise (PRN) correlation receiver and the backup Space Ground Link System (SGLS) receiver.
    • A Geometric Moment Bounding Algorithm

      King, Maurice A., Jr.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      There are many important problems in the field of communications theory whose solution is the expectation of a function of a random variable. Examples include linear interference problems such as intersymbol interference and co-channel interference. In these cases, it is often not computationally feasible to evaluate the expectation exactly. This paper presents an algorithm that will compute tight upper and lower bounds to generalized moments of a broad class of random variables. The procedure is based on an isomorphism theorem from Game Theory. The technique is easily understood while yielding excellent results for this class of communication problems.
    • Gigabit Detectors for Visible Space Laser Communications

      Green, Samuel I.; McDonnell Douglas Astronautics Company (International Foundation for Telemetering, 1978-11)
      Performance data taken on several candidate high data rate laser communications photodetectors are presented. Measurements of bit error rate versus signal level were made in a 532 nm system at 500 Mbps.
    • GPS Overview and User Equipment Antijam Design

      Hemesath, Norbert B.; Hutchinson, William M.; Rockwell International (International Foundation for Telemetering, 1978-11)
      The Global Positioning System (GPS) features an all-weather global coverage navigation sensor with 0.01-nmi positioning accuracy. In the following paper, GPS is described with emphasis on antijam considerations developed in the USAF AFAL Generalized Development Model, GDM. Section 1 provides an overview of the GPS ground, space, and user segments. Section 2 describes antijam issues and techniques applicable to GPS. Section 3 describes the GDM design with emphasis on antijam. features. The objectives of the paper are thereby threefold. The first is to give an overview of GPS, how it works, its participants, and its status. The second is to provide a tutorial discussion of spread spectrum receiver design related to GPS (some knowledge of signal processing principles is therein assumed). The third is to provide an example of GPS receiver design which incorporates antijam features.
    • The GPS Satellite and Payload

      Codik, Andrew; Gronlund, Robert A.; Rockwell International Corporation (International Foundation for Telemetering, 1978-11)
      The NAVSTAR/Global Positioning System Satellite is briefly outlined as is the technique for navigation using signals from such satellites. A description of the GPS navigation subsystem with emphasis on its microprocessor and its interfaces and software routines is given.
    • GPS User Equipment, A Concept in Modular Design

      Candy, Donald W.; Hoover, Wayne M.; Texas Instrument Incorporated (International Foundation for Telemetering, 1978-11)
      A brief introduction to the Global Positioning System is presented. Functional modularity of GPS User Equipment systems and subsystems is studied. Physical modularity and commonality of hardware and software functions are discussed with respect to Design To Cost (DTC) and Life Cycle Cost (LCC) goals. Commonality of hardware and software support systems is explored with respect to increased development efficiency. Finally, a composite overview of the Texas Instruments High Dynamics and Manpack Vehicular User Equipments is presented with emphasis placed on the use of technology and vertical integration for DTC/LCC.
    • A Hardware Comparison of Intermicroprocessor Communications Techniques

      Korgel, C.; Lohaus, T.; Pape, D.; Martin Marietta Corporation (International Foundation for Telemetering, 1978-11)
      A generalized multimicroprocessor utilizing the TI9900 and AMD2901 microprocessors is presented. Different types of microprocessors are used to provide extensive computational capability, versatile interprocessor communications, high reliability, and system flexibility. The system is especially suitable for high speed signal processing, data processing, and data handling. Measured data on the speed of interprocessor communication for three techniques is presented along with a comparative assessment of flexibility and reliability for the techniques.
    • High Density 42-Track Magnetic Tape System

      Montgomery, J. H.; Martin Marietta Corporation (International Foundation for Telemetering, 1978-11)
      Design and development of a 42-track high density magnetic tape system for the NASA SEASAT program is described. Both record and playback at a nominal 120 megabits per second from a single data stream was achieved on a 1-inch mylar tape with bit error rate better than 1 x 10⁻⁶ without error correction. Solutions are presented to the requirements of data encoding, high bit rates, recovery from tape dropouts, and efficient use of tracks. This now operational system features a Channel Performance Status Panel, a Tape Bypass Mode, and a MUX/DEMUX unit capable of operating at 150 megabits per second.