• MULTIMEGABIT OPERATION MULTIPLEXER SYSTEM

      Giri, Ronald R.; Maxwell, Marvin S.; Radiation; Goddard Space Flight Center (International Foundation for Telemetering, 1973-10)
      The Multimegabit Operation Multiplexer System (MOMS) is a high data rate PCM telemetry unit capable of sampling and encoding 60 scanning radiometer and 4 vidicon channels at 250 kilosamples/second and 5 megasamples/second, respectively. This sampling capacity plus the 7-bit quantization requires a total throughput rate of 40 megasamples/second and 280 megabits/second. To produce these rates efficiently, the system was divided into a pair of identical 140-megabit blocks. A low-power 20-MHz analog multiplexer and analog-to-digital converter were developed together with a video sample-and-hold that features an aperture time error of less than 50 picoseconds. Breadboard testing of these basic building blocks confirmed the design prediction that the total system would consume 27 watts of power. Two 140-megabit output ports are suitable for quadraphase modulation.
    • A REVIEW OF MULTIPLE AMPLITUDE-PHASE DIGITAL SIGNALS

      Smith, Joel G.; California Institute of Technology (International Foundation for Telemetering, 1973-10)
      This paper reviews the data rate, error rate, and signal-to-noise ratio relationship for various uncoded M-ary digital amplitude modulation (AM), phase modulation (PM), and combined AM-PM systems. These signal systems have the common virtue that expanding the number of possible signals to be transmitted increases the data rate but not the bandwidth. The increased data rate generally requires an increased signal-to-noise ratio to maintain constant error probability performance. Thus, these systems use power to conserve bandwidth. A general treatment of the error rate of M-ary digital AM-PM permits development of a simple yet accurate expression which approximates the increase in average signal-to-noise ratio (over that of binary phase shift keying) required for constant error performance. This equation provides insight into why arrays differ in their signal-to-noise ratio requirements.
    • ADAPTIVE ANTENNA ARRAY

      Smith, James M.; Sielman, Peter F.; AIL (International Foundation for Telemetering, 1973-10)
      A key problem in establishing and maintaining high quality communication repeater links among users, where the vehicle for retransmission is a synchronous orbit communications satellite, is that of enhancing the limited effective radiated power (ERP) capabilities of the smaller user against the not always so limited ERP capabilities of co-users or other sources of rf interference. The adaptive array which can supply narrow high gain custom shaped individualized beams weighted to reflect the ratio of user power to thermal noise and at the same time minimize the capacity reducing effects of intentional or unintentional rf interference emitters appears to be the most effective means of improving overall performance at least system cost.
    • RELAY TECHNIQUES FOR MOBILE SERVICES

      Vandenkerckhove, J.; ESRO/ESTEC (International Foundation for Telemetering, 1973-10)
      Dr. Vandenkerckhove will discuss system considerations involved in providing communications services to aeronautical and maritime users via Synchronous Relay Satellite.
    • AIFTDS-4000, A FLEXIBLE HIGH SPEED DATA ACQUISITION SYSTEM

      Borek, Robert W.; Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
      The data acquisition system of today’s research aircraft generally consists of a multiplicity of “black boxes” linked together by wiring cables of various lengths and sizes. This approach offers the user an “off-the shelf” type of flexibility to which he has become accustomed. It does not, however, provide for all the needs of an results demanded by today’s technology. The rising costs of flight test hours, the sophisticated airframes, and the minimum flight time allotted for actual flight test indicate a need to review existing data acquisition system technology and apply up-to-date technology. The NASA Flight Research Center at Edwards, California, initiated a review of its needs in the area of airborne data acquisition systems. The result was a new and powerful system called “AIFTDS-4000” (Airborne Integrated Flight Test Data System). AIFTDS is a high speed computer-controlled PCM system comprised of three basic units, the remote multiplexer de-multiplexer unit, the PCM processor, and the memory unit. The three units were designed and tested to meet the requirements of pertinent Mil-Specs for high performance aircraft. The signal conditioning, sensor excitation, and time code generator were designed as an integral part of the system and are not separate chassis. This paper discusses the design objectives established prior to actual hardware construction and compares these objectives with the final hardware.
    • TIME DOMAIN ANALYSIS OF AN AGC WEIGHTED COMBINER

      Hill, E. R.; Naval Missile Center (International Foundation for Telemetering, 1973-10)
      The conventional agc weighted diversity combiner is implemented on the assumption that the agc system of each receiver is tracking the rf fading envelope perfectly (i.e., such as to maintain the linear i-f output amplitude constant). The departure from optimum (maximal-ratio) combining which results from imperfect tracking is determined by computer solution of the nonlinear differential equation of the agc system for particular deterministic rf fading envelopes. The performance of the agc weighted combiner is compared with maximal-ratio and equal-gain combiners, both as a function of time and fade rate. It is shown that under certain conditions the equal-gain combiner outperforms the agc weighted combiner. It is also shown that by using both the a-m (detected linear i-f envelope) and the agc voltages for weighting the combiner the limitations arising from the response time of the agc system can be overcome. It is also indicated how an optimum diversity selector can be implemented by using both the a-m and agc voltages.
    • AN ALL DIGITAL LOW DATA RATE COMMUNICATION SYSTEM

      Chen, Chi-Hau; Fan, Maisie; Southeastern Massachusetts University (International Foundation for Telemetering, 1973-10)
      The advent of digital hardwares has made it feasible to implement many communication system components digitally. With the exception of frequency down conversion, the proposed low data rate communication system uses digital hardwares completely. Although the system is designed primarily for deep space communications with large frequency uncertainty and low signal-to-noise ratio, it is also suitable for other low data rate applications with time-shared operation among a number of channels. Emphasis is placed on the fast Fourier transform receiver and the automatic frequency control via digital filtering. The speed available from the digital system allows sophisticated signal processing to reduce frequency uncertainty and to increase the signal-to-noise ratio. The practical limitations of the system such as the finite register length are examined. It is concluded that the proposed all-digital system is not only technically feasible but also has potential cost reducation over the existing receiving systems.
    • INTERFEROMETER SIGNAL DEMODULATION IMPROVES TRACKING SENSITIVITY

      Cooper, William K.; New Mexico State University (International Foundation for Telemetering, 1973-10)
      A considerable improvement in signal to noise ratio has been achieved in narrow band interferometer trackers by demodulating the telemetry signal prior to the final stage of i-f amplification. This system has an effective signal bandwidth much greater than the noise bandwidth. Signal to noise improvements of 10 dB are typical.
    • A HIGH CAPACITY, HIGH DATA RATE INSTRUMENTATION TAPE RECORDER SYSTEM

      Bessette, O. E.; Radio Corporation of America Recording Systems (International Foundation for Telemetering, 1973-10)
      A 240-megabit/second, serial bit stream recording system using a longitudinal (fixed-head) magnetic recording technique called HDMR (High Density Multitrack Recording) has been developed. This system provides maximum bits per square inch of tape at reliable in-track packing densities. Unique “unitized” fabrication techniques have been used to construct single stack magnetic heads (record/play on the same head) at track densities of over 100 tracks per inch. Commercially available tape is accommodated by the use of error detection and correction. HDMR technology, applied to the implementation of a typical ground instrumentation recording system, allows key performance parameters of: 240 Mb/s serial data input, 108 in/s tape speed, a 142-track head, a bit error rate of 1 x 10^-6 and 240 Mb/s serial data output.
    • USER-ORIENTED IMAGE DATA CARTRIDGE RECORDING SYSTEM

      Horton, Charles R.; Radio Corporation of America (International Foundation for Telemetering, 1973-10)
      New generation satellites such as ERTS present a new challenge to the data recording industry. Continuous wideband data creates an enormous storage/retrieval problem. Recently developed high density tape storage solves the volume problem but does not provide fast access. Clearly, some cartridge type device is required. A similar problem faced the broadcast T.V. industry. Cartridge equipment was developed to allow automatic programming of short segments. This paper describes application of this technology to present and future data storage requirements. With the technique described, ERTS data can be segmented into blocks of ten frames each and stored in easily accessed tape cartridges.
    • CROSSPLAY COMPATIBILITY OF WIDE-BAND TAPE RECORDER/REPRODUCERS

      Hartzler, F. R.; Hust, D. R.; Heberling, E. D.; Naval Missile Center (International Foundation for Telemetering, 1973-10)
      This paper describes the procedure and results of a series of tests on a cross section of tape recorders to determine the effects of record bias and record signal level on the quality of data recorded in the Pre-D (predetection) mode. FM (frequency modulation) and PCM (pulse code modulation) formats were used in the study. The tests were performed on tape recorders at five test sites to determine the effects of crossplay under typical operating conditions. The results are summarized and possible methods of improving crossplay data quality are suggested.
    • TRACKING AND DATA RELAY SATELLITE SYSTEM (TDRSS)

      Barritt, Paul; Clark, George; NASA (International Foundation for Telemetering, 1973-10)
      Coincident with the advent of the Space Shuttle era in the late 1970’s will also come a new era in space communications. The NASA Tracking and Data Relay Satellite System (TDRSS), consisting of satellites in synchronous orbit relaying data between mission spacecraft in low altitude earth orbit and the various mission control centers, will change the character of tracking and data acquisition operations from the short duration, intermittent contacts characteristics of the world wide network of ground stations of the Space Tracking and Data Network (STDN), to nearly full time contact. This capability will expedite interaction between ground based scientists and their spaceborne instruments, reduce dependence upon data tape recorders, and in general improve the reliability and versatility of space communications. This paper will discuss the requirements for TDRSS service and the characteristics of the system and subsystems that NASA studies have shown best meet those requirements.
    • International Telemetering Conference Proceedings, Volume 09 (1973)

      International Foundation for Telemetering, 1973-10
    • TELEMETERING VIA LEAKY WAVEGUIDES

      Hu, A. S.; New Mexico State University (International Foundation for Telemetering, 1973-10)
      Telemetering through leaky waveguides is a combination of cable transmission and atmospheric transmission. This system carries radio signals in a confined space tube thus making signal transmission through tunnels, mines, and buildings possible. This paper discusses the history of development, the types of leaky waveguide, the transmission characteristics, and the performance evaluation methods.
    • TIMING CORRELATION IN TELEMETRY RECORDING AND PROCESSING SYSTEMS

      Matthews, F. L.; Streich, R. G.; Vandenberg Air Force Base (International Foundation for Telemetering, 1973-10)
      The Space and Missile Test Center (SAMTEC) has conducted tests to correlate independent data stream to within ±10 microseconds. System timing error measurements have been made to determine RF system delays; the delays associated with wideband analog tape recorders in the recording, dubbing and reproducing processes; and uncertainties associated with processed data. Comparison of the time delays between predetection PCM data and post-detection PCM data are made. Several methods of recording IRIG time code formats A and B are evaluated for best resolution. Timing error versus tape recorder head azimuth is plotted. Tape recorder phase delay effects on time code formats and on PCM data are given. The time bias between the time tag and the computer processed data is presented. Sources of timing errors and the calibration and operating techniques available to minimize these errors are discussed. A special time tag technique (Ref 1) has been used in the past to determine the cumulative timing bias for all sources. This investigation is believed to be the first attempt to identify the individual contributions to the cumulative bias.
    • MULTISTATE ANALOG AND DIGITAL INTEGRATED CIRCUITS

      Abraham, George; US Naval Research Laboratory (International Foundation for Telemetering, 1973-10)
      Several independent physical phenomena in unipolar and bipolar semiconductor pn junction devices and integrated structures lead to voltage and current-controlled negative resistance without the use of external feedback. These include avalanche breakdown, quantum mechanical tunneling, and minority carrier storage. Two complementary types of negative resistances may be utilized as a basis for generating multistable energy levels. The number of stable states and their relative spacings can be readily varied. Without negative resistance interaction, M+1 stable states can be generated where M is the number of negative resistance devices involved. With negative resistance interactions, additional multistability occurs, resulting in a total number of (M+1) + (M-1)!stable states. S-S, N-N, and S-N interactions are analyzed. In the latter case, complementary negative resistances can be made to annihilate each other. Multistate tunnel and avalanche negative resistances have been made to occur in single devices resulting in tristable, quadristable and higher order energy levels. Variable radix counters, oscillators, frequency dividers, and high density memory elements have been fabricated both as hybrid and monolithic integrated circuits.
    • THE INFLUENCE OF CARRIER FREQUENCY ON SNR FOR FM SYSTEMS

      Monson J. E.; Harvey Mudd College (International Foundation for Telemetering, 1973-10)
      The influence of carrier frequency on broadband signal-to-noise ratio is derived for a frequency modulated tape recording system. Optimum signal-to-noise performance occurs at the value of carrier frequency where the carrier-to-noise ratio is falling at 6 dB/octave. Signal-to-noise ratio is relatively insensitive to changes in carrier frequency about the optimum value.
    • PRINCIPLES AND HEAD CHARACTERISTICS IN VHF RECORDING

      Krey, K. H.; Lieberman, A. G.; Harry Diamond Laboratories; University of MD (International Foundation for Telemetering, 1973-10)
      Concepts of VHF analog magnetic recording are discussed; problem areas are reviewed; and solutions are outlined. Attention is drawn to the conductive-gap-spacer recording head. The unique field contours of this recording head with Alfesil pole faces are analyzed in relation to the recording of very short wavelengths. The field gradients of the unloaded head are computed for various conditions such as maximum magnetization depths, positions in the tape coating, and gap lengths. Comparison of the driven-gap-spacer head using Alfesil pole faces with the ferrite driven-gap-spacer head and the conventional ring-core head shows the Alfesil type to be the most effective for a-c bias VHF recording at very short wavelengths. Problems associated with short-wavelength recording and reproduction are reviewed. In spite of good short-wavelengths capabilities of the Alfesil head, the requirement for a high head-to-tape speed continues to be mandatory to minimize wavelength reproduction losses.
    • PERFORMANCE OF A 350-Mb/s ADAPTIVE EQUALIZER

      Ryan, Carl R.; Stilwell, James H.; Motorola Inc. (International Foundation for Telemetering, 1973-10)
      This paper applies baseband adaptive equalization techniques to rf multipath and transmitter/receiver distortions. Included are test results comparing 350-Mb/s adaptive equalized and unequalized receivers. These comparisons are made with distortion typically encountered in a high data-rate line-of-sight microwave system such as demodulator quadrature errors, demodulator phase offset errors, and moderate rf multipath distortion. The design and construction techniques are also illustrated.
    • AN ULTRAHIGH RATE DIGITAL TAPE RECORDER FOR SPACECRAFT APPLICATIONS

      Thompson, C. R.; Treadwell, R. J.; Powell, C.; FICA; NASA (International Foundation for Telemetering, 1973-10)
      Spaceborne digital recorders must satisfy the conflicting requirements of maximum data storage of high rate data (particularly for high resolution sensor data) and a long life with high reliability (meaning rugged design and moderate head-to-tape speeds). The multitrack longitudinal (fixed head) recorder can successfully resolve this conflict and satisfy both requirements. The evolutionary machine described herein was originally designed to store and reproduce 30 min of 39.9-Mb/s sensor data, for mission lives on the order of 1 year; newer designs have surpassed these parameters by significant amounts.