• Phase Linearity in Telemetry Reception

      Ghais, Ahmad F.; Ferrari, Eugene J.; Boardman, Charles J.; ADCOM, Inc. (International Foundation for Telemetering, 1967-10)
      The problem of phase nonlinearities in telemetry-receiving systems is studied. The principal data-degrading effect is shown to be intermodulation distortion of FDM telemetry signals. Another form of data degradation, namely, intersymbol interference in TDM telemetry signals, is found not to be related directly to phase nonlinearities, but rather to the transient response of the receiving system. The noise-loading technique is introduced as an effective means of characterizing, analyzing and measuring intermodulation distortion. Some analytical results are cited relating the amount of intermodulation distortion to signal and receiving-system parameters. Analytical details are omitted, the emphasis being placed on interpreting the significance of the results to the telemetry systems engineer. The experimental verification of these relationships is briefly reviewed. The results are used to establish quantitative tradeoffs between the performance parameters of receiving systems. These tradeoffs are then used in formulating methods of specification and design to ensure high data quality.
    • On-Line computer Monitoring-Immediate Interpretation of the Electrocardiogram

      McAllister, James; Caceres, Cesar A.; Medical System Development Laboratory (International Foundation for Telemetering, 1967-10)
      The purpose of this paper is to provide some insight into the continuous monitoring and computer analysis of medical signals, in particular the electrocardiogram which has been chosen as a model. The advantages of having continuous data analyzed by an accurate, objective system are elaborated. The great mass of data being collected has heretofore been stored and forgotten in many instances but with immediate computer analysis the interpretation of trends and rapid physiological changes are easily and rapidly manifested. In addition, statistical evaluation of the data through programming te techniques can lead to new diagnoses and treatments and allows the monitored data to be compared with "pre-obtained" data as well as other groups of people.
    • International Telemetering Conference Proceedings, Volume 03 (1967)

      International Foundation for Telemetering, 1967-10
    • Redundancy Removal Algorithms Applies to Gemini XII Data

      Jory, H. M.; McDonnell Douglas Corporation (International Foundation for Telemetering, 1967-10)
      This report presents the results of a company funded computer study to deter-mine the effectiveness of redundancy removal algorithms as applied to manned spacecraft data. The company familiarity with and access to manned space flight data provided an almost unique opportunity to study this method of data compression using data representative of that which will be required from a Manned Mars Mission. A total of 28,500 seconds of the Gemini XII flight is examined using seven algorithms and three different tolerance bands. Over eleven million samples have been examined using terminology and descriptions consistent with previously published literature to allow direct comparison of actual flight data with previous results using synthetic data. The outputs from the computer presented the following information: A. Compression ratios as a function of technique, channel number and type of data for each of the activity periods. B. Buffer input rates and accumulated queue lengths every 2.4 seconds for the ZFN technique. C. Error distribution, for each of the techniques for six different apertures. The results indicate that the zero order - variable corridor - adjusted preceding sample transmitted (ZVA) technique can provide data compression ratios of 187:1 using a 1.2% tolerance. Nominal buffer sizes of 20K bits are adequate to handle the data activity period involved. The error distribution evaluation indicates that the error distribution is primarily a function of the technique and the aperture.
    • Error Rates in Wide Band FSK with Discriminator Demodulation

      McRae, Dan; Radiation Incorporated (International Foundation for Telemetering, 1967-10)
    • Adaptive PCM Pattern Synchronization

      Van de Houten, R. S.; Dynatronics, Inc. (International Foundation for Telemetering, 1967-10)
      The trend toward more automated PCM decommutation systems demands less operator intervention in their operation. A weak link in this progression has been in the implementation of group synchronizer strategy. A new synchronizer has been developed based on the optimum properties of sequential probability ratio testing which requires only one program based on required worst case decision error probabilities and which is independent of the PCM format being synchronized. A mathematical model is formulated which accurately describes the operating characteristics of this technique. These operating characteristics are then compared to conventional synchronizer characteristics which demonstrate the superiority of this approach. The decision process described inherently adapts to signal conditions by making decisions faster and with less chance of error as bit error rate decreases. Only the Check Mode is discussed, but the same techniques apply to the Lock Mode.
    • An Experimental Evaluation of PAM-NRZ/FM

      Heberling, E. D.; Naval Ordnance Laboratory (International Foundation for Telemetering, 1967-10)
      The results of a hardware evaluation of PAM-NRZ/FM are presented along with a description of the conditions under which the data were taken. State-of-the-art commutators, transmitters and receivers procured from commercial sources were utilized in the evaluation tests. The principal characteristics of PAM-NRZ/FM considered were data channel response, performance at low signal-to-noise ratios compared to equivalent FM/FM and PCM/FM systems, linearity, crosstalk, overmodulation, transmission noise, data resolution, decommutator synchronization and a comparison of performance at commutation rates of 25,000, 100,000 and 250,000 samples per second. The test data indicates that PAM-NRZ/FM is capable of 2 to 5 percent data transmission accuracy and that performance at low RF levels is comparable to that of FM/FM or PCMJFM under the test conditions specified.
    • Some Analysis of the WSMR Test Results on DSB

      Nichols, M. H.; Duke University; Duke University | White (International Foundation for Telemetering, 1967-10)
      The purpose of this paper is to relate results of ref. (1), the previous experimental paper, Double Sideband Suppressed Carrier System, by F. J. Schmitt, to theory and to the application of DSB/FM to wideband vibration type data. Inasmuch as the notch noise test was one of the basic tools for the laboratory investigation, the notch noise results and the DSB results are compared. Preliminary data on the effects of tape recording, including flutter, are discussed. Comparison of CBW FM/FM and DSB/FM for vibration telemetry is made on the basis of requirements outlined in ref. (2). The experimental data indicate a 13 to 18 db carrier power improvement of DSB/FM over FM/FM. Reasons for this improvement are given.
    • An Integrated 16-Channel Differential Analog Multiplexer

      Rudin, M. B.; Botchek, C. M.; Rotunda, R. F.; Fairchild Semiconductor (International Foundation for Telemetering, 1967-10)
      The salient characteristics of a multi-channel differential MOS analog multiplexer are presented and compared with the requirements of time division telemetry systems discussed in the paper, "A Family of Linear Integrated Circuits for Telemetry," by M. B. Rudin and R. L. O'Day. Particular emphasis is given to the more important terminal parameters -- channel R(on) variation, switching speed, channel leakage and crosstalk, protection against spurious signals, and power supply requirements. It is shown that this type of design is acceptable for both high and low level signals. The MOS supply levels are special, and some speculation is presented on how future designs could use supplies more compatible with bipolar needs.
    • Analysis of Multiplex Systems Based on Orthonormal Function Groups

      Balas, Mark J.; Harry Diamond Laboratories (International Foundation for Telemetering, 1967-10)
      Linear multiplex systems may be represented as sequential, invertible transformations on a message set. Such transformations are based on orthonormal functions in the Hilbert space of square-integrable functions. Demultiplexing is accomplished with the inner product which results in high immunity to noise and bandlimiting. When the orthonormal functions form a multiplicative group, easily generated pulse functions arise. Methods are presented for determining these function groups and their corresponding algebras which yield simple and useful multiplex systems.
    • Anticipated Problems of Re-Entry Vehicle Telemetry at UHF

      Numrich, Fred H.; General Electric Company (International Foundation for Telemetering, 1967-10)
      Present information on missile range planning indicates that serious UHF telemetry coverage problems are likely to occur during reentry of ballistic vehicles. Flight test experience at VHF has demonstrated that receiving stations experience difficulty in tracking re-entry vehicles under conditions of rapid changes of signal strength caused by combinations of vehicle motion, vehicle antenna pattern, and plasma attenuation. Similar but greater variations at UHF coupled with narrow beamwidths and reduced sensitivity of re-entry stations portend greater problems at UHF. Conical scan systems may prove inadequate. Comparisons of similar telemetry systems at VHF and S-band are presented, demonstrating that received signal to noise ratios at re-entry stations will be 3 to 9 db below levels Presently obtained at VHF for reentry stations. The narrow antenna beamwidths (1° to 3.5°) will also cause problems in acquisition so that some form of acquisition aid will be required at each station. Omnidirectional antennas currently used in aircraft at VHF will be useless at UHF. Ships and aircraft will require stabilized or compensated antennas. Acquisition of hypersonic targets will be a particularly severe problem for aircraft receiving stations. In addition to defining the re-entry problem, system limitations, and expected effects, this paper also makes recommendations to range planners and users to minimize or correct the anticipated problems.
    • Telcom-Time Variable Telecommunications Performance Prediction Program

      McQuaid, B. L.; Fashano, M.; Hughes Aircraft Company (International Foundation for Telemetering, 1967-10)
      The TELCOM program has been developed to aid in the design and analysis of spacecraft telemetry and communication systems. Given a spacecraft trajectory, it is often desired to predict the total received power of the transmission link. Since the gains and losses of the individual link components are dependent on the spacecraft trajectory, as well as the spatial orientation of the spacecraft, the received signal power varies as a function of time along the flight path. TELCOM organizes the time variable information and calculates the received signal power in the subcarrier and/or carrier predetection bandwidths at specified time intervals. The spacecraft trajectory information and. antenna gain contours are stored on magnetic tape. The time in-variant quantities are provided by the user so that he may easily make parametric studies to determine the effect of link constants on system performance. TELCOM output options include printed values of received signal power at specified. time intervals, plots of signal power, range, look angle versus time, and DB margin summaries at specified points along the trajectory.
    • A Short Range Underwater Biotelemetry System

      Steadman, John W.; Convair Division, General Dynamics (International Foundation for Telemetering, 1967-10)
      The requirement for monitoring the physiological functions of the test subject in weightlessness simulation activities coupled with the advantages of using telemetry for such monitoring led to the development of a biotelemetry system. One valuable technique for simulation of weightlessness uses the neutral buoyancy obtained by having the subject under water, which leads to a requirement that the telemetry system work in this medium. Previous underwater telemetry systems have usually used ultrasonic carriers. The system described in this paper is unique in providing a multiple channel underwater telemetry system using an electromagnetic carrier. The development of transducers used with this system to provide information on the work load Imposed by various simulation tasks is also described.
    • Transmission of Direct Blood Pressure from Dogs During Obedience Training

      Rader, R.; Sears, W. J.; Reid, D. H.; Meehan, J. P.; Henry, J. P.; University of Southern California, School of Medicine (International Foundation for Telemetering, 1967-10)
      A method for transmission of direct blood pressure from dogs during obedience training, treadmill exercise and sleep is described. Solid state transducers, 6.5 mm diameter, were implanted in the abdominal aorta of healthy young mongrel dogs. The design of the specialized circuitry required to detect and transmit blood pressure data is presented. Calibration was performed by comparing direct and transmitted data. An obedience training course provided emotional arousal, and for physiological stimuli the animals exercised on a treadmill at various grades and speeds up to exhaustion. Blood pressures taken during natural sleep were defined as basal for each animal. Representative observations are noted to emphasize the practical benefits of advanced biotelemetry in research.
    • Graphical Determination of Third Order Intermodulation Frequencies in RF Systems

      Jeske, Harold O.; Sandia Corporation (International Foundation for Telemetering, 1967-10)
      A simple discussion is given on the origin of intermodulation distortion in nonlinear devices concluding with reasons for placing primary interest on third order products. Nearby third order products are located at 2f(x) – f(y) and f(x) + f(y) – f(z) where f(x), f(y), and f(z) represent all frequencies in a group. The number of nearby IM products of this type is equal to N(N - 1) (1 + (N - 2 / 2)) where N is the number of input frequencies to the nonlinear device. For eight input signals, for example, a total of 224 intermodulation products are produced that are located in a bandwidth that is three times the bandwidth between the highest and lowest input frequencies. The graphical method of locating intermodulation products is rapid and simple. Basically, interfering frequencies are found by the alignment of two pieces of paper. On each piece of paper, the spacings between all input frequencies are plotted on a linear scale. Frequencies which may cause interference are easily identified. A guide which will allow the selection of frequencies to avoid third order intermodulation interference is also given.
    • Summary and Discussion of Signal-to-Noise Ratio Improvement Formulae for FM and FM/FM Links

      Rechter, Robert J.; Hughes Aircraft Company (International Foundation for Telemetering, 1967-10)
      Frequently, a need exists to compute the postdetection (recovered data) signal-to-noise ratios (SNR) in a given frequency modulated (FM) or double frequency modulated (FM/FM) transmission link; alternately certain postdetection SNR requirements are established, and the link's parameters must be correspondingly specified. In either case, relationships that clearly relate postdetection SNR to link parameters, for either FM (or FM/PM) or FM/FM links, are useful to the telemetr system designer. Although such relationships have been stated in varying degrees of applicability, and rigor of derivation, it has been the author's experience that the sources are scattered, and often not sufficiently explicit. Further, the deviations from the mathematically ideal situation are often overlooked. It is the purpose of this paper to present useful SNR improvement formulae for the general FM and FM/FM case (both for IRIG and non-IRlG multiplexes), and also present data that takes nonideal postdetection filtering into account.
    • On-Line Computer Tuned S-Band Phase-Lock Receiver

      Van Wechel, Robert J.; Counter, James M.; Interstate Electronics Corporation (International Foundation for Telemetering, 1967-10)
      Long-loop phase-lock receivers utilize a voltage-controlled crystal oscillator (VCXO) as the first local oscillator (LO). Tuning across a band of frequencies with such an arrangement has been virtually impossible in many of the existing space and satellite tracking equipments; the characteristics of the long-loop configuration have necessitated the use of VCXO's. One particular advantage of the long-loop, the capability of maintaining coherent LO and reference frequencies for coherent demodulation of all IF outputs, is a constraint on the receiver system described here. One approach for multi-channel operation has been to employ one VCXO for each frequency; this has obvious economic limitations in applications requiring many channels. For stations used in multiple vehicle tracking, frequency-agile or frequency-hopping anti-jamming applications, or for nearly unlimited tuning capability in a data gathering station it is desirable to use a frequency synthesis technique to tune the receiver. Such a synthesizer should lend itself to on-line computer control. It is the intent of this paper to describe a technique of digital synthesizer tuning for a long-loop S-band phase-lock receiver. Hardware utilizing this technique is now in operation at Marshall Space Flight Center and Kennedy Space Center. The synthesizer provides both direct-reading pushbutton and computer tuning; frequency changing can be accomplished in microseconds. The frequency band 2200-2300 MHz is covered in 0.1 Hz steps. Although capable of providing on-line computer controlled operation, the system is presently being operated in the manual mode.
    • The Effect of Random Threshold Levels on PCM Quantization Noise

      Kern, R. J.; General Electric Spacecraft Department (International Foundation for Telemetering, 1967-10)
      It is common with PCM systems to consider a uniform quantization noise (or error) distribution over plus or minus one half the quantization level. This distribution must be modified to describe the effect of uncertainties in the location of the decision thresholds which separate adjacent quantization levels. The uncertainties exist because electronic decision circuits trigger somewhere within a narrow band surrounding an intended voltage instead of at exactly that voltage. In this paper the encoding error distributions, are calculated in terms of the distributions of the threshold locations. It is shown that the variance of the quantization noise is increased by an amount almost exactly equal to the variance of the threshold uncertainty distribution. The effect of the uncertainty bands becomes noticeable only where the uncertainty band is an appreciable part of the quantization interval. Prime examples are systems with small voltage differences between encoding levels such as low-level systems (0 to 50 millivolts) and systems with large number of quantization levels. Because error variance is related to the square of the uncertainty range, a threshold uncertainty range of 1/10 the quantization interval will increase the net encoding variance by approximately (1/10)² or 1.0%.
    • Multichannel, Free-Flight Base Pressure Telemetry in Wind Tunnels

      Choate, R. H.; ARO, Inc. (International Foundation for Telemetering, 1967-10)
      Radio telemetry techniques permit the acquisition of aerodynamic data from free-flight models in wind tunnels, a method which ensures that the data are completely free from support interference effects. No serious difficulties were experienced in the development of a telemetry system to record simultaneously four channels of base pressure data from a free-flight model; however, precautions were necessary to prevent interactions between channels and to prevent interference between telemetered and extraneous signals. This telemetry system is based upon small, transistorized, transmitter units, placed aboard the model, which are directly modulated (FM) by capacitance-type pressure transducers. All units are powered from a single battery package. These units, one for each data channel, transmit to antennas located outside the tunnel. All units are interchangeable between models, and have built-in provisions for preselecting full-scale pressure range (0.0005-0.1 psid) to provide optimum data resolution under a variety of test conditions in three different wind tunnels (at nominal Mach numbers of 8, 10, and 20). Oscillograph traces resulting from tests of typical models, both in free flight and on a sting mount, are compared and discussed from an instrumentation point of view. Satisfactory system operation is demonstrated by comparing telemetered base pressure data to data obtained by conventional means during a test of a sting-mounted model.
    • A Low Noise Low Drift Monolithic Integrated Operational Amplifier

      Fullagar, D. J.; Fairchild Semiconductor (International Foundation for Telemetering, 1967-10)
      An operational amplifier is described which has been designed specifically for applications where low noise and low drift are of primary importance. The factors affecting noise and drift are discussed, and the methods used to minimize these outlined. For low level signal amplification purposes the performance is shown to be superior to currently available designs.