• Analog- Digital LSI on the E⁺ᵗ Curve

      Constant, R. N.; Lekven, C. M.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      The title of this paper was selected to indicate that large scale integration (LSI) of analog (linear), digital and combined monolithic analog and digital (A & D) circuits for telecommunication systems is progressing at an exponential rate. As is the case with exponential functions, near term (i.e., when t is small) increases are rather modest, but, once started, the function grows rapidly. This is the case of A & D LSI: it is just starting to take hold, and impressive gains are expected in the future. The purpose of this paper is to explore, from the system point of view, some of the recent technology developments that have taken place and that are expected to impact the design of future telemetry, communication and sensor equipment.
    • 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.
    • 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.
    • LSI Hardware for Data Communications

      Comisar, Gerald G.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      A review is presented of some new, low-cost, easy-to-use hardware for interfacing small-scale digital systems to telecommunications and data link networks. Devices featured are binary serial interfaces, protocol controllers (including SDLC and HDLC), data encryption units (including the new NBS Federal Standard), modems, and information encoders. Compatibility with existing microprocessors and future trends are discussed.
    • A Multiple FSK Microprocessor Demodulator/Decoder

      Sahmel, Rainer H.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      A demodulator is described that utilizes an interrupt-driven 8-bit microprocessor and an external digital counter to demodulate an 8-ary Frequency-Shift-Keyed input signal. After demodulation, the system correlates received groups of symbols with a stored code to derive and maintain character synchronization, and compute the decoded and error corrected output. The total device package count is less than 10, including the microprocessor with integral read/write memory and clock driver circuits, a Parallel Interface Adapter, a 1024 X 8-bit ROM, an 8-bit digital counter, a two-pole filter, a limiter and complete input and output buffering.
    • Satellite Communication Simulation and Its Applications

      Wang, Lily L.; Yeh, Paul P.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      The computer simulation activities which have been carried out at The Aerospace Corporation for satellite link performance studies and system analysis are reported. A brief description of the modelings of a filter, nonlinear device, modulator, detector and receiver is also given. Some results from the simulation studies, such as the basic link performance in the presence of filters and nonlinear device (hard limiter or TWT), the comparisons of various modulation techniques (OK-QPSK, MSK and PFQPSK), the study of cross talk in a FDMA system, the interference or jamming at the presence of a nearby source, and finally, the intermodulation problem of a multiple channel MFSK system using the frequency hopping, are addressed.
    • Solid State Microwave Power Amplifiers - An Overview

      Lewinter, S. W.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      This paper summarizes results that have been achieved with various types of microwave solid state power amplifying devices and presents some projections of advances that can be expected within approximately a five year period. The frequency band surveyed extends from 1 to 100 GHz. The emphasis is on CW or high duty cycle pulse applications, where long life is of great importance, such as in a satellite communication system. The types of devices considered include the gallium arsenide field-effect transistor (GaAs FET), IMPATT diodes, bipolar transistors, Gunn diodes, TRAPATT diodes and electron bombarded semiconductor (EBS) devices. An overview of the technology of microwave power combiners is also included.
    • Spread Spectrum and Coding Techniques in Communication Systems

      Gerardi, F. R.; Otsuki, W. T.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      With the increase in complexity of military communications networks, a combination of spectrum spreading and error correction coding is typically required to provide adequate antijam protection. The specific system architecture utilizing these techniques is established in this presentation by performance requirements, system constraints, interface problems, and assumed jammer models. This presentation will describe various processing techniques with emphasis on their interactions and limitations. Two spread spectrum techniques for permitting operations in a jamming environment are considered: direct sequence (PN) and frequency hopping. The advantages and limitations of each technology will be discussed. The antijam capability of these spread spectrum systems can be improved by using various error correction coding schemes. These can (make more efficient use of the bandwidth allocation) as well as provide enhanced protection against pulse and tone jammers. The advantages, limitations, and constraints imposed on a communication system using various combinations of these techniques are discussed with particular emphasis on the system performance.