• Microwave and Millimeter Wave Semiconductor Devices

      Fank, F. Beringer; Central Research Laboratories (International Foundation for Telemetering, 1978-11)
      Steady progress has been made this past year in nearly all microwave semiconductor technologies. Improvements in power, frequencies of operation, noise characteristics and perhaps most important at this time, reliability, have been made with GaAs FETs, GaAs Impatts, Silicon Impatts, and InP Gunn diodes. The latest state of the art as well as commercially available performance levels of each of these devices will be discussed. Both areas of microwaves and millimeter wave semiconductor devices will be covered as new millimeter wave systems requirements are pushing this technology to the forefront of development. The area of high peak powers with high average power have given an impetus to the renewed development of GaAs Impatts. Power combining techniques with these Impatts have led to replacement of medium power tubes. Present performance characteristics in single and combined technologies will be given. The expected trend for these "standard" devices over the next several years will be forecast along with a discussion of some new potential device technologies.
    • 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.
    • High Performance Circulators, Isolators and Electronic Waveguide Switches

      Piotrowski, Wieslaw S.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1978-11)
      This paper presents the results of a most recent high technology development program that has led to significant state-of-the-art advances in the design and development of circulators, isolators and electronic waveguide switches at microwave and millimeter wave frequencies. These components are constructed by the use of an analytical design procedure. They are characterized by excellent electrical and environmental performance and feature a simple mechanical configuration, which results in significantly reduced prices. These units are presently commercially available from Aertech Industries, Sunnyvale, California, a TRW subsidiary.
    • Spectral Shaping Without Subcarriers

      Welch, Lloyd R.; University of Southern California (International Foundation for Telemetering, 1978-11)
      For proper operation of the phase lock loop which tracks a carrier it is important to minimize the spectral energy at frequencies near the carrier. A traditional method is to modulate the data onto a subcarrier in such a way that there is little energy near D.C. The resulting signal then is used to modulate the carrier. The problem with such a scheme is that the total bandwidth is much larger than necessary to transmit the data. This paper proposes and analyzes a simpler scheme which increases the data bandwidth by a very small fraction, yet reduces the energy near D.C. to nearly zero.
    • A Microprocessor Controlled Antenna Pointing Unit

      Kasser, J. E.; COMSAT Laboratories (International Foundation for Telemetering, 1978-11)
      Two prototype antenna pointing units (APUs) for controlling different antennas tracking geostationary satellites have been built using an 8080 microprocessor. The use of the microprocessor has allowed the same basic hardware to control two separate and different parabolic dish antennas with minimal circuitry changes and has provided significant flexibility in the performance of the units. This paper describes the APU design, which optimizes hardware and software to provide the flexibility necessary during initial testing and subsequent operation of the prototypes.
    • Computer Controlled Testing of Telemetry Ground Stations

      Law, Eugene L.; Pacific Missile Test Center (International Foundation for Telemetering, 1978-11)
      The testing of telemetry ground stations by manual methods can be very time consuming. The test time can be reduced by using an automated test system. A minicomputer controlled test system is described and is shown to provide accurate, repeatable results and to reduce the test time to about one-fifth of the manual test time.
    • Application of a Technology: The Case of Fiber Optics and MIL-STD-1553

      Meador, Terrance A.; Naval Ocean Systems Center (International Foundation for Telemetering, 1978-11)
      Guidelines for the utilization of fiber optics transmission technology in the design of a standardized aircraft multiplex system interconnect have been difficult to establish. MILSTD-1553 is imprecise in the separation of transmission and operational functions with the result that the substitution of fiber optics for wire transmission specifications is impractical without redefinition of the 1553 word formats and data bus architecture.
    • The Navstar Global Positioning System Control Segment Performance During the First Year

      Schaibly, John H.; General Dynamics (International Foundation for Telemetering, 1978-11)
      This paper reports the preliminary performance of the Navstar Global Positioning System Control Segment (CS) during the period July 1977 through July 1978. During this period, three navigation satellites were launched and were tracked and uploaded by the CS. An overview of the CS is presented as well as a summary of the present system status. User performance, total system performance, and CS performance are discussed, and methods for determining the latter are described. Performance measures including first measurement residuals and predicted pseudorange error for NTS 2 and first measurement statistics, predicted User Range Error, ephemeris prediction error, and predicted clock error for the NDS satellites are presented. The preliminary performance results presented are very good considering the early stage of multi-satellite tracking. Projecting the two satellite performance to four satellites, the CS contribution to user navigation error is 12.8-20.5 meters at 2 hours. This error consists of ephemeris and clock prediction errors of approximately 3.5 and 4.5 meters, respectively.
    • TDRSS - User Satellite Acquisition and Tracking

      Franklin, S. B.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1978-11)
      The Tracking and Data Relay Satellite System (TDRSS) will provide communications and tracking services to the Space Shuttle and most other NASA missions of the 1980's. Relay services are provided between NASA's near earth satellites and a ground terminal at White Sands, N.M. via synchronous Tracking and Data Relay Satellites. Establishing and maintaining the communications links is a complex task which includes spatial, signal and data acquisition involving crosslinks between the TDRS and NASA's user satellites. Concepts and capabilities are presented for antenna acquisition, and for PN code and carrier acquisition. Total acquisition times, including bit synchronizer and decoder acquisition are also provided.
    • 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.
    • Simulation of Two Bandwidth Efficient Modulation Efforts in Satellite Communications

      White, Brian E.; The MITRE Corporation (International Foundation for Telemetering, 1978-11)
      A bandpass limited satellite channel with uplink and downlink noise was simulated for several constant envelope modulation schemes. Minimum shift keying (MSK) significantly outperformed quadriphase shift keying (QPSK) in achieving bit error rates of 0.005 with less than 1 dB degradation for a channel bandwidth to data rate ratio B/R = 0.78, for example. Frequency division multiple access (FDMA) scenarios with unsynchronized satellite signals were also simulated. A processing satellite performed the functions of Doppler and symbol timing correction and demodulation of each uplink. Additional filtering mitigated intersymbol interference (ISI) deliberately introduced for spectral shaping by prolate spheroidal data windows. Even when the received power in each satellite signal was 10 dB above the desired signal, 16 kbps rate-1/2 coded QPSK satellite signals on odd 12.5 kHz centers could coexist with line of sight (LOS) signals on 25 kHz centers. These results are applicable to the ever growing problems deriving from increased spectral occupancy.
    • Performance Evaluation of Communication Channels by Computer Simulation

      Poza, H. B.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1978-11)
      A computer simulation model capable of aiding in the design and predicting the performance of complex end-to-end communication systems is described in this paper. The model is used to choose the optimal modulation scheme under certain communication channel constraints, define the signal distortion characteristics introduced by realizable channel components and select the demodulator/bit synchronizer designs for minimization of bit error rate. A parameter sensitivity analysis is conducted to demonstrate the usefulness of the model in evaluating the effect of different signal distortion phenomena on overall link performance.
    • 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.
    • High Linear Density Recording Study

      Levy, Avner; Bell & Howell (International Foundation for Telemetering, 1978-11)
      A series of tests were conducted in an attempt to study the recording behavior of Enhanced Nonreturn to Zero (ENRZ) code at high linear recording densities. Using the "eye" pattern as a criteria in the first phase, the tests clearly demonstrate the sensitivity of a tape recorder to the DM (Delayed Modulation) coding technique as compared to ENRZ. For the same linear density, ENRZ has a considerably wider margin than the DM code. In the second phase of that study, a series of tests were conducted using high energy tape and magnetic heads with reproduce gaps in the order of 12 μin, referred to as "double bandwidth heads." Using present day technology, it was possible to demonstrate linear packing density never before achieved on magnetic recording tape.
    • Serial High Density Digital Recording Using an Analog Magnetic Tape Recorder/Reproducer

      Law, Eugene L.; Pacific Missile Test Center (International Foundation for Telemetering, 1978-11)
      A great deal of interest is being generated in the area of high density digital recording (HDDR) because of the need to record high rate digital signals. This paper presents the results of a study where digital data was recorded on ordinary analog magnetic tape recorder/reproducers using several of the currently popular codes. It is shown that bit packing densities of 25 kilobits per inch (or higher) are achievable with analog wideband 2.0 MHz recorder/reproducers.
    • A Class of Programmable Satellite Receivers

      Klare, Stephen W.; Motorola, Inc. (International Foundation for Telemetering, 1978-11)
      The currently developed theory of optimal demodulation and synchronization systems for digital data has been applied to the design of a class of programmable satellite receivers. The primary purpose is to provide flexibility in application through digital control of the important functions of the receiver. This permits the acquisition and demodulation of medium to very low data rates in widely varying communications environments and over a broad range of modulation schemes. The receiver peripherals are controlled by a digital processor which can accept external commands to reconfigure to any of a preprogrammed set of algorithms.
    • Location of Cross-Correlation Sidelobes of PN Sequences

      Gold, Robert; Robert Gold Associates (International Foundation for Telemetering, 1978-11)
      In this note, we show how the cross-correlation pattern of certain classes of linear PN sequences may be determined and described as a linear shift register sequence. Knowledge of the location of the correlation sidelobes may then be exploited in the application of these codes to spread spectrum communication systems. As an example of such an application, a characterization of the relative phase of a received code in terms of the pattern of cross-correlation sidelobes with a locally generated code is presented.
    • Impact of Microcomputers on Telemetry and Telecommunications

      King, J. B.; Flight Systems, Inc. (International Foundation for Telemetering, 1978-11)
      The next computer revolution is under way. The first computer revolution impacted government and big business; the current revolution is affecting small businesses, schools and homes. The demands that will be placed on the telemetry and telecommunications industry in the next decade are mind-boggling. New products, new techniques and new jobs must be developed to respond to that demand. This paper presents future applications of microcomputers in communications and what that portends for our society.
    • Telemetry - Past, Present, Future

      Strock, O. J. "Jud"; EMR-Telemetry (International Foundation for Telemetering, 1978-11)
      On the assumption that "the past is prologue", this paper presents an interesting and revealing look at the telemetry technology of twenty years ago, a comparison of that with the technology of today, and an extrapolation into the future of telemetry. Factors which are examined include the characteristics of telemetry systems, the price per unit of performance, and the applications in which telemetry has been, is being, and likely will be used. The key word in the paper is "choice". A user or prospective user had little choice in equipment or techniques twenty years ago; the present day technology offers a wide range of choices; indications are that the future will offer even greater choices in characteristics and price - and consequently, in the applications for which telemetry is a viable tool for data acquisition and processing.
    • A SEASAT Synthetic Aperture Radar Preprocessor (SARP)

      Waltz, Edward L.; Bendix Aerospace Systems Division (International Foundation for Telemetering, 1978-11)
      A Synthetic Aperture Radar Preprocessor (SARP) for the SEASAT radar is described. The SARP system permits playback of Synthetic Aperture Radar (SAR) data for digital processing into ocean imagery. The system includes a High Data Rate Recorder, SAR Digital Preprocessing (SDP), array processor, mass storage disc, and host computer. Data tapes are played back at reduced rates and the SDP performs the functions of frame synchronization, decommutation of time and status data, presummation of adjacent azimuth returns and correction of gain as a function of range. The data are formatted into presummed range returns and are transferred to the array processor for buffering and subsequent storage on the mass disc. This preprocessing operation loads a 100 x 100 km swath of data on the disc for subsequent range and azimuth correlation to convert the SAR data to imagery. The SAR Data Preprocessor equipment is described and the implementation of the 35 Mbps frame synchronizer and presum arithmetic logic are detailed. A SAR Test Pattern Generator for simulation of SAR and other image data formats is also described. The test generator permits simulation of a wide range of digital data formats (including NASA and IRIG standards) and includes a programmable data pattern capability.