• A New Comcept for Equalization of Magnetic Tape Reproduce Systems

      Byers, Robert A.; Bell & Howell Company (International Foundation for Telemetering, 1970-10)
      A new approach to the problem of equalizing direct reproduce channels of instrumentation tape recorders has been developed. The technique employed utilizes active circuits and signal processing to develop the required transfer function. The principal advantage of the approach is that it requires only one operational adjustment to obtain the equalization characteristics. This allows a significant reduction in operator setup time and an increase in reliability by the reduction in the number of variable circuit elements. This is achieved by a slight increase in overall circuit complexity, the effect of which is minimized by the repetitive use of simple, functional circuits. The overall system approach is suitable for hybrid or monolithic technology.
    • Noiseless Linear Feedback and Analog Data Tranmission

      Butman, S.; California Institute of Technology (International Foundation for Telemetering, 1970-10)
      It is well known that noiseless linear feedback achieves channel capacity for the additive Gaussian channel. It has also been shown that it can be used to achieve the rate-distortion bound on the mean squared error for an arbitrary Gaussian source sent over the infinite bandwidth white Gaussian channel. However, it is shown here that noiseless linear feedback by itself does not suffice when the channel is bandlimited. It is shown that, out of the more than countable variety of Gaussian sources that ordinarily exist, only a countable subset can be transmitted via the bandlimited noiseless feedback link at the theoretical efficiency predicted by Shannon's rate-distortion bound. Thus, some nonlinear operations are necessary in almost all cases even with feedback.
    • Notch Noise Loading Data on Baseband Tape Recording

      Heideman, W. R.; Nichols, M. H.; Aerospace Corporation (International Foundation for Telemetering, 1970-10)
      Notch power ratio tests were performed on a magnetic tape recorder/ reproducer, using direct recording in the baseband. For the equipment tested, it is concluded that the IRIG method of setting the record power level as that which produces 1% third harmonic on a single tone, does not necessarily result in an optimum record/reproduce cycle. It is concluded that the input and output levels should be set with reference to notch noise test data to optimize baseband tape recording performance for baseband recording of frequency division multiplexed systems. In order to interpret the notch noise data, it was necessary to assume two non-linear processes, one acting in conjunction with the record process and one in conjunction with the playback process.
    • On Linear Information-Feedback Schemes for White Gaussian Channels

      Fang, Russell J. F.; COMSAT Laboratories (International Foundation for Telemetering, 1970-10)
      For the transmission of a Gaussian information source over an additive white Gaussian-noise (AWGN) channel, several noiseless, linear-feedback schemes are shown to be the same in the sense that they not only achieve the rate-distortion bound on the minimum attainable mean-square error (MSE), but also possess identical system parameters. These equivalent schemes can be easily applied to solving the problem of optimally matching a colored Gaussian source with an AWGN channel. These equivalent schemes can further be employed to send messages from digital information sources over AWGN channels. It can be shown that any of these equivalent schemes as a decision-error probability which is the smallest among the class of all linear schemes. The condition of noiseless feedback can be relaxed to cover the more general noisy information-feedback case. A suboptimal scheme is proposed for transmitting data from a Gaussian source, whose output process has a power spectral density function which is uniform in some frequency range and zero elsewhere, over some AWGN channels to some destination. This suboptimal noisy feedback scheme can also be used to send data from a digital information source over an AWGN channel with better performance than can be achieved without noisy feedback.
    • Optical Processing Interfaces

      Shulman, Arnold Roy; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      A brief introduction to coherent optical data, processing is given. Several problems are discussed concerning the implementation of coherent optical data processing for general use. The major problems discussed are concerned with the imaging qualities of coherent systems and the material requirements for recording these images. The solution to several problems is presented and the state-of-the-art in other areas is indicated.
    • 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.
    • 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.
    • Pre-Emphasis for Constant Bandwidth FM Subcarrier Oscillators for FM and PM Transmitters

      Campbell, Allan; Sandia Laboratories (International Foundation for Telemetering, 1970-10)
      This paper shows that the proper pre-emphasis for the inputs of constant bandwidth subcarrier oscillators into an FM transmitter is a straight line through the origin, and into a PM transmitter is one of equal amplitude for all subcarrier oscillators. The proper method for calculation of the pre-emphasis for a mixture of channel bandwidths is to use the square root of the bandwidth ratio of the subcarrier channels for both FM and PM transmitters. Examples are given.
    • Processing of NRZ PCM from 10 MB/Sec to 200 MB/Sec

      Gray, J. S.; Radiation Systems Division (International Foundation for Telemetering, 1970-10)
      The type of functions required to optimally process PCM plus noise are the same at low and high bit rates. At high bit rates there are severe constraints in synthesizing these functions due to limitations of present day devices and logic; and due to extrinsic effects of networks over broad baseband bandwidths. Techniques developed for signal conditioning, bit synchronization, group synchronization, and decommutation of NRZ PCM from 10 Mb/sec to 200 Mb/sec are presented. Multiple techniques were investigated in each area over the complete bit rate range of interest to ascertain performance versus complexity and cost effectiveness among different techniques at different bit rates.
    • A Projectile Telemetry System for In-Barrel Data

      Bentley, R. D.; Ruttle, C. J.; Sandia Corporation (International Foundation for Telemetering, 1970-10)
      Sandia Corporation is developing a projectile telemetry system and required ground support to monitor the performance of components mounted in a 155 mm projectile. The telemetry system is to provide the data link required to monitor component performance during and following launch from a 155 mm "long-tom" cannon. The projectile experiences a 16,500g setback acceleration of 15 msec duration coupled with an angular acceleration of 328,000 rad/sec². A P band FM/FM telemetry system has been developed to provide a data link while the projectile is in the barrel as well as out of the barrel. The technique has been successfully tested in a 155 mm projectile with a setback acceleration of 12,500g 20 millisec duration and in a 81 mm mortar round with a setback acceleration of 7,000g 7.5 millisecond duration. A parachute recovery system is used to obtain a "soft" recovery of the 155 mm projectile mounted components and telemetry system.
    • 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.
    • Signal Designs for Apollo Scientific Data Systems

      Hood, B. H., Jr.; Dawson, C. T.; Loch, F. J.; NASA Manned Spacecraft Center (International Foundation for Telemetering, 1970-10)
      The Apollo lunar-exploration missions are being planned for the purpose of obtaining comprehensive scientific data. The system descriptions and key signal-design considerations for two data transmission systems - the Phase II Scientific Data System and the Particles and Fields Subsatellite - are discussed. In both cases, the designs are constrained by the requirements to (1) use the existing spacecraft systems where possible, (2) use the existing ground stations, and (3) maintain the existing Apollo communications capabilities.
    • 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.
    • 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.
    • Telemetering in Thermobiology: A Study of Mammalian Hair

      Davis, Stanley D.; Case Western Reserve University (International Foundation for Telemetering, 1970-10)
      An evaluation of the effectiveness of hair as insulation in a cold environment was performed using radio telemetry. Two adult male rats, telemetered for deep body temperature, were placed in an 18°C environment. After five days of monitoring temperature, food intake and body weight, each animal was shaved of all hair and observed an additional five days. Following shaving, both rats increased food intake, lost weight and showed lowered mean daily body temperatures, though in only one was the latter significantly lower. The increased metabolism after shaving was estimated to be between 25.2% and 51.1% greater than the preshave value in one animal, and between 23.4% and 32.9% in the other. The lowest increases were recorded in the rat tolerating the lower mean temperature. On the basis of food intake alone, metabolic demands of the shaven rats at 18°C were shown to be equal that of normal rats at 12°C. The advantages of using telemetry and continuous monitoring of temperature is discussed with regard to the results of this experiment.
    • Telemetry and Communications to Apollo Flight Controllers

      Glines, Alan; Lazzaro, Joseph A.; NASA Manned Spacecraft Center (International Foundation for Telemetering, 1970-10)
      The focus of this paper is on the use of telemetry and communications as essential tools in Apollo flight operations. The operational capabilities of the spacecraft and ground systems are described briefly to provide a background for detailing the management of the Apollo data system. The Mission Control Center is the central point of the operations and the recipient of all real-time Apollo data. Therefore, the operational structure within the mission operations control room is outlined briefly, with emphasis on the flight controllers who are the prime users and manipulators of telemetry data. The Instrumentation and Communications Officer (INCO) and the Operations and Procedures Officer (PROCEDURES) in the mission operations control room are responsible for the compatibility control of both the spacecraft and ground telemetry and communications systems. Their mission duties in four areas are detailed: (1) space-vehicle/ground communications compatibility, (2) telemetry subcarrier and bit-rate control, (3) spacecraft antenna management, and (4) data retrieval. The INCO and the PROCEDURES, through effective management of the many communications-systems modes of operation, maximize the amount of preferred real-time and playback data being transmitted to the Mission Control Center. The importance of the data is illustrated by specific mission events from the Apollo 11, 12, and 13 missions.
    • A Universal L-Band Telemeter for Use on Artillery Projectiles and Gun Launched Research Probes

      Richard, Victor W.; Hadowanetz, Wasco; Aberdeen Proving Ground; Picatinny Arsenal (International Foundation for Telemetering, 1970-10)
      A UHF (1520 MHz) telemetry system for use with artillery projectiles and gun launched research probes is described. The feasibility of a universal telemeter (UTM) is demonstrated which is based on the use of modular plug-in components available to meet a variety of instrumentation requirements, including ogive and rear mounting, thus, eliminating the need for the development of a special projectile telemetry unit for each application of in-flight projectile performance monitoring or gun probe experiment. The special, ruggedized components and techniques for pre-flight high acceleration testing are described. The components described include: broadband, omnidirectional antennas for ogive and base mounting in projectiles; a high gain, all polarization, fan beam receiving antenna; stabilized, high efficiency UHF transmitters; miniaturized voltage controlled oscillators; 8 and 16 channel commutators; button cell and g-activated reserve cell batteries; shock resistant, electrically compatible radome and encapsulating materials; modular assembly cases; and ogive and base mounted telemeter test projectiles. The physical and electrical characteristics of the components of the telemetry system are presented, along with laboratory and field performance data obtained from firing standard, 155 mm, spinning projectiles, including the reception of signals while the projectile is in the gun barrel.
    • The Upper Bounds of the Confidence Intervals of Bit Error Probabilities Based on a Markov Chain Bit Error Model

      Mizuki, M.; Vandenberg Air Force Base (International Foundation for Telemetering, 1970-10)
      Confidence intervals for the bit error probability of an actual PCM telemetry data can be determined based on the analysis of received redundant bits. The procedure usually requires the assumption of independence of bit errors. However, bit errors may occur in clusters under various conditions of multipath, injection of nonthermal noise of long duration, and bit jitters. As a representation of bit errors in clusters, a Markov chain model is introduced. Some results on the confidence interval of bit error probability are obtained as functions of a Markovian parameter, which designates the degree of departure from the binomial model. The computations are quite laborious compared to the case of the binomial model. This paper gives step-by-step instructions for computing the probabilities that r error bits occur among mn received bits which can then be used for the derivation of the confidence interval.
    • 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.
    • VHF/UHF Antenna Calibration Using Radio Stars

      Taylor, Ralph E.; Stocklin, Frank J.; Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      This paper describes a stellar calibration technique, using radio stars, that determines receiving system noise temperature, or antenna gain, at frequencies below 500 MHz. The overall system noise temperature is referenced to radio star flux densities known within several tenths of a decibel. An independent determination of antenna gain must be made before computing system noise temperature and several methods are suggested. The preferred method uses celestial and receiving system parameters to compute gain; whereas a less desirable method requires an accurately known output level from a standard signal generator. Field test data, obtained at 136 MHz and 400 MHz in the NASA space tracking and data acquisition network (STADAN), demonstrates that antenna gain and system noise temperature can be determined with an accuracy of 1 db. The radio stars Cassiopeia A and Cygnus A were used to calibrate 40-ft. diameter paraboloidal antennas, at 136 MHz and 400 MHz, and phase array antennas at 136 MHz. The radio star calibration technique, described herein, makes possible accurate station-to-station performance comparisons since a common farfield signal source is observed. This technique is also suitable for calibrating telemetry antennas operating in the IRIG 216-260 MHz frequency band.