• Performance Evaluation Medthos for PCM Bit Synchronizer/Signal Conditioners

      Peavey, B.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      PCM Bit Synchronizer/Signal Conditioners (BSSC) possess 3 basic performance characteristics which directly affect the processing of PCM telemetry data. These characteristics are: bit error rate (BER), bit slippage rate (BSR), and bit sync acquisition (BSA). This paper describes proven methods to meaningfully, and accurately measure these characteristics with particular emphasis on BSR and BSA. These methods require relatively simple and inexpensive procedures and instrumentation, and could be used by manufacturers and users to evaluate and acceptance test BSSC. The basic principle employed in these methods is "fixed threshold frame synchronization" with a unique strategy. Thus, there is no requirement for bit delay between the reference and BSSC output data, and synchronization of the reference data in the comparator with the BSSC output data takes place automatically. Moreover, this approach to testing BSSC represents the actual situation in which the BSSC would be operating as part of the telemetry data system, and hence would provide a direct measure of system performance. In actual application, these methods proved to be very effective and accurate for input SNR of E(b) /N(0) > O dB, and slightly less accurate for E(b) /N(0) < O dB (data having more than 10% errors). In general, BSA and BSR measurement accuracies of 20-30 bits can be achieved. A detailed discussion of accuracy is presented in the paper. In addition, the BSR and BER measurement methods are applicable to assessing the performance of tape recorders (TR) as it affects the actual system performance, rather than just the peculiar TR characteristics of TBE (time base error), bit dropout, and wow and flutter.
    • Manned Space Flight Network Telemetry System

      Underwood, Thomas C., Jr.; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      This paper discusses the Manned Space Flight Network (MSFN) Telemetry System as it has been developed through the Mercury, Gemini, and Apollo programs and is now being modified to meet Skylab, Earth Resources Technology Satellite (ERTS), and Apollo "J" mission (Apollo 16 and subsequent lunar missions) requirements. The existing telemetry system must be modified to meet the requirements of these future programs. This modification will consist of the implementation of automated configuration switching, centralized control of telemetry subsystems, tunable FM and PSK modulators/ demodulators, high frequency PCM signal conditioners, and the upgrading of both the wide band instrumentation magnetic tape recorders and the PCM decommutation capability. The resulting telemetry system, which will be capable of supporting various manned and unmanned space missions, is described here. Data flow diagrams are delineated and equipment electrical characteristics are discussed.
    • Format and Address Equation Generation by Computer

      Leighou, R. O.; Hill, K. H.; Martin Marietta Corporation (International Foundation for Telemetering, 1970-10)
      Addressable remote multiplexed time division telemetry systems are being used more and more. Most of these systems operate with serial addresses generated by a central unit where each data source has a unique address. Thus the address sequence determines the particular format. In one type of system, the address sequence is determined by transfer logic between a counter and an address shift register. It takes several man-weeks of effort to develop a format and the logic equations to implement the address sequence for that format. To avoid this effort, an algorithm and computer program that generates the formats and the logic equations has been developed and is described. The program data inputs are: the basic format configuration of addresses (channels or data sources) per frame and the frames per master frame; and the number and types of channels at each samples per master frame (S/MF) rate. The program outputs are: address assignments by program ID, telemetry formats sequences with program ID, and the set equations for the address output shift register. Several checks are made during the program and if program restrictions are violated or format generation is impossible, error messages are printed and the program may be halted.
    • PCM Processing in Bandpass Signals

      Shaver, F. H.; Aerospace Corporation (International Foundation for Telemetering, 1970-10)
      Several types of errors are generated when a bandpass analog signal is sampled such that it can be encoded into a sequence of digital words. Two of these types of errors are particularly dependent on the frequency band occupied by the input signal. These are: (1) the aliasing errors due to generation of unwanted spectral components and, (2) pulse width errors due to the use of finite width, flat topped pulses when regenerating-the analog signal. Expressions are presented for the spectral densities and total power of these error sources. The particular dependence of each on the location in frequency of the input signal is investigated and discussed. Quantization noise and distortion due to the smoothing filter which is used to reconstruct the signal are not considered in this paper. It is determined that the aliasing noise power as a function of the ratio of the signal center frequency to the sampling frequency has a series of relative minimums and maximums. A relationship defining the ratios at which the minimums occur is presented. An approximate formulation for the sample pulse width error is presented which allows a simple estimate of its magnitude to be made without knowledge of the smoothing filter transform or the sampling frequency. Quantitative results are presented as a function of the percentage bandwidth of the signal and the ratio of the sample pulse duration to the period of the center frequency of the signal. The results of the analyses are interpreted as design constraints.
    • Manned Space Flight Network Unified S-Bond System 1970

      Spearing, R. E.; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
    • Effects of Instrumentation Recorder time Base Error on Spectral Purity

      Leeke, P. D.; Minnesota Mining and Manufacturing Company (International Foundation for Telemetering, 1970-10)
      Experimental data is presented to show how carrier amplitude of a recorded signal is affected by Time Base Error. Time Base Error effects on the sideband structure of a recorded signal are also shown for different amounts of Time Base Error and at several frequencies. The effect of capstan servo adjustment on spectral purity demonstrates the need for new methods of performance evaluation to achieve optimum performance when recording spectrum information. The data presented shows that skew (ITDE) has little effect on spectral purity for analysis bandwidths of 50 Hz or greater.
    • The Effects of Using a Finite Number of Bits and Approximate Division in a Data Compressor

      Bjorn, T., Jr.; Harshman Associates, Inc. (International Foundation for Telemetering, 1970-10)
      In the design of a data compressor one of the basic problems is error due to the use of a finite number of bits in calculating various parameters. This is error due to truncation (or round off) after a set number of bits to the right of the binary point. Another error that could be introduced to the system is that error caused by the use of an approximate divide instead of a full divide. It is the purpose of this study to find the effect of these two errors so that (1) a judgment may be made as to how many bits to the right of the binary point are necessary, and (2) find if a double shift approximate divide may be used instead of the slower full divide. The study is divided into three basic parts (1) the effect of truncation (or round off), (2) the effect of the double shift approximate divide, an (3) the combined effect of truncation (or round off) and the double shift approximate divide. Each one of these error-causing phenomenon has two variations; i.e., an error caused while compressing data and an additional error caused while reconstructing. The error during compression distorts the tolerance limits, and the error in reconstruction causes distortion of the reconstructed line segment. Each of the errors leads to an overall error in data magnitude over and above the normal allowable error of one tolerance level. For all of the analysis the maximum run length of the compressed data is assumed to be 128. A summary of the study is found in Table 6.
    • Machine-to-Machine Compatability in Wideband recording

      Levy, Avner; Ampex Corporation (International Foundation for Telemetering, 1970-10)
    • Analysis of the Modified Integrate and Dump Decision Device

      Quinn, Mathew J., Jr.; Hayre, H. S.; NASA Manned Spacecraft Center; University of Houston (International Foundation for Telemetering, 1970-10)
      The purpose of this paper is to describe a system which exhibits better bit error rates for Frequency Shift Keying (FSK) signals than those now used to make the bit decision The system is similar to the popular Integrat6 and Dump device., but it is modified to take advantage of the information contained in the FM "clicks" resulting from the demodulation process to aid in making the proper bit decision. The paper is divided into four parts: First, a brief review of the Integrate and Dump Detector is presented. Then the "click" mechanism is described and such properties of this mechanism as the number of "clicks" in a channel are reviewed. Third, a method of using the information in the "clicks" to one's advantage is discussed. Fourth, and finally, the hardware needed to implement such a system is described in general and certain suggestions are made to improve the over-all decision making capabilities of the system.
    • Disc Recording: Signal Acquisition and Reduction

      Calfee, R. W.; Data Disc, Incorporated (International Foundation for Telemetering, 1970-10)
      During the last several years, magnetic recording on plated discs has been developed and now can be applied to instrumentation recording. The disc recorder is available in a fixed head configuration for multichannel parallel recording and in a moving head configuration for one or two event parallel recording with extended time. The disc recorder can capture transient analog signals with bandwidth from DC to 6MHz or more for periods of time from microseconds to 20 seconds or more. The analog signal is stored on the disc after being processed through a proprietary period modulator. The disc recorder allows the user a natural base from which to reduce the analog data to computer understood words. Data reduction equivalent to 100 megabit conversion is possible at data rates compatible with the data device. Thus the disc recorder can capture transient analog signals and will allow simple data reduction.
    • Field Testing of Telemetry Systems

      Pickett, R. B.; Vandenberg Air Force Base (International Foundation for Telemetering, 1970-10)
      Tests have been developed and implemented at the Western Test Range for calibration of telemetry receiving systems. The tests serve an additional function as diagnostic aids.
    • L- and S-Band Antenna Calibration Using Cass. A or Cyg. A

      Taylor, Ralph E.; NASA Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      This paper describes a stellar calibration technique, using the absolute flux density from Cassiopeia A or Cygnus A, to determine effective antenna gain, or system noise temperature, at the IRIG L- and S-band frequencies. Paraboloidal dish antennas, ranging from 20 feet to 85 feet in diameter, can be calibrated using a total-power conventional RF receiver. Previous investigators utilized a Dicke radiometer to perform the same function. It is recommended that the Cass. A and Cyg. A flux densities, known within several tenths of a decibel, be utilized to calibrate IRIG antennas located on the North American Continent. It is demonstrated that Cass. A and Cyg. A provide sufficient signal power to calibrate a 20-foot diameter dish antenna; dish antennas up to 85-feet in diameter may be calibrated without applying a beam correction factor. Precision values of absolute flux density for Cass. A and Cyg. A are given for the 1700-1710 MHz space research, and IRIG 1435-1540 MHz and 2200-2300 MHz bands. An accurate radio sky map is also provided that may be scaled in frequency for the various bands.
    • Instrumentation Systems Engineering Management

      Warren, J. R.; Norton Air Force Base (International Foundation for Telemetering, 1970-10)
      Examples of practical, effective, tools for the management of systems engineering have been presented. The usage of those tools is further examined. Management, as used here, pertains to the technical management of the systems engineering Job. The techniques described are structured around a medium/large data transmission/ acquisition/processing system. The principles can be applied to other systems also. Fundamental to the discussion is the use of models, criteria, and selected data for evaluation which results in decisions and program direction for systems optimization.
    • Studies of Life Before Birth

      Mackay, R. Stuart; Boston University Medical School (International Foundation for Telemetering, 1970-10)
      By surgical procedures, small physiological monitoring transmitters are placed within the body of fetal animals within the uterus of the mother. After a brief recovery period, various parameters are followed before, during, and after birth, the little animals being born with functioning transmitters already in place. The purpose of such studies is to determine normal values of various cardiovascular parameters in relatively undisturbed subjects and also to follow surgically-produced anatomical and physiological defects which mimic congenital embryologic abnormalities with the goal of learning to cope with these through fetal surgery. Transmission of fetal vectorcardiograms and intrauterine pressure will be described.
    • A Computerized Data Management Methodology for the Minuteman Instrumentation System

      Foust, L. D.; TRW Systems (International Foundation for Telemetering, 1970-10)
      The tasks associated with Development Management of complex instrumentation systems, from initial concept to production, involves the utilization of very large quantities of data. It is impossible to acquire, process, and analyze this data entirely by manual means, therefore, automated data management systems have been conceived to solve this type of problem. The computerized data system developed by SAMSO MINUTEMAN Instrumentation System Engineering Management is described and is further illustrated by presenting some of the specific applications of the system.
    • Use of an Error Model and a Simulation Program to Support Technical Management

      Brown, L. O.; Baum, R. F.; TRW Systems (International Foundation for Telemetering, 1970-10)
      This paper contains a discussion of various computer programs and their interconnection with an "error model" which have been developed and are being used by TRW, to form a very useful tool for technical management of a missile development and testing program. General aspects and requirements of the simulation and of some subroutines are outlined. A review of possible error sources is made emphasizing their effect on the frequency tracking performance of a typical instrumentation system such as the FPQ-6 radar operating with a radar transponder installed on the target.
    • Synchronization of Pseudo Noise Sequences for PCM Testing

      McClellan, Wade C.; Nichols, M. H.; White Sands Missile Range; Duke University (International Foundation for Telemetering, 1970-10)
      Coherent and noncoherent methods of synchronizing PN sequences for testing PCM telemetry receiving stations are compared. Test results are given for each method using a typical range S-band receiver, bit synchronizer and tape recorder. Effects of time-base-error from the tape are calculated and checked by test results. The laboratory tests indicated that for bit-error probabilities less than 0.01, the noncoherent synchronizer functioned satisfactorily.
    • A Long Term Remote Intragastric pH, Temperature, Motility and Electrical Activity Monitoring System

      Wise, Leslie; Jones, Paul W.; Womack, G. J.; Ballinger, Walter F.; Washington University School of Medicine; McDonnel Douglas Astronautics Company (International Foundation for Telemetering, 1970-10)
      The system under development can monitor intragastric physiological changes over time periods exceeding fourteen days. Prior to this development, long term intragastric measurements were impossible in freely mobile subjects. The electronic instrumentation includes a tethered sensor capsule, automatic titration unit, telemetry system, and data display. The system requires minimal maintenance during the prolonged monitoring period. The sensor capsule utilizes a pH sensitive glass electrode with wet reference, a thermistor, a solid state pressure sensitive transducer, and impedance matching electronics which develop the physically related electrical signals. Signal acquisition is via tether hardline to the multichannel telemetry unit and subsequent RF transmission to a central data receiving system for display and storage. Automatic titration functions, a myograph to record voluntary muscle movement, and the measurement of skin resistance as an indicator of stress, may also be included in the telemetry data. Capsule system tests in vitro indicate these accuracies: ± 0.2 pH units over a range of 1 to 10 pH; ± 0.2°C over a temperature range of 25°C to 45°C; and ± 10% over a pressure range of 0 to 15 inches of water. Life tests of the capsule in vitro show useful life times of the order of 30 days. Preliminary human in vivo experiments have confirmed the capsule sensitivity and stability.
    • International Telemetering Conference Proceedings, Volume 06 (1970)

      International Foundation for Telemetering, 1970-10
    • Quartz Crystals Units for High G Environments

      Bernstein, M.; U.S. Army Electronics Command (International Foundation for Telemetering, 1970-10)
      Quartz crystal units are commonly used to achieve frequency accuracy of the order of 100 parts per million or better. The usual crystal mechanical environments are quite benign compared with those encountered In high g telemetry, however, and the normal shock tests are only 100 g's. The preliminary, design of a ruggedized high frequency crystal unit is shown as well as test date on the behavior of these units when subjected to 15,000 g's of impact shock. A crystal resonator is quite fragile since at 20 MHz an AT resonator is only 3 thousandths of an inch in thickness. Higher frequency units appear to have a g limit only slightly in excess of 20,000 g's. At lower frequencies, the resonator is not the limiting element but the supports and bonds become unreliable. A trade-off must be made between a very stiff support, which will increase the acceptable g level, and the concomitant frequency instability due to changes in mechanical stress on the quartz resonator. These stress changes can be caused both by differential thermal expansion of the mount and quartz as well as by shock Induced effects.