• Double Sideband Suppressed Carrier Telemetry System

      Schmitt, F. J.; Lockheed Electronics Company (International Foundation for Telemetering, 1967-10)
      Vibration, shock, and acoustic data constitute one of the principal requirements for wideband telemetry. In order to permit a quantitative comparison of DSB/FM with the experimental results on constant bandwidth FM/FM for telemetry wideband noise-like data, a laboratory investigation has been conducted at WSMR. This paper reports experimental data on RF spectrum occupancy, intermodulation, performance against thermal noise, and some preliminary data on the effects of tape recording.
    • 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.
    • 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.
    • 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.
    • A Quantitative Impedance Pneumograph

      Bergey, George E.; U.S. Naval Air Development Center (International Foundation for Telemetering, 1967-10)
      An impedance pneumograph capable of quantitatively measuring respiratory volumes is described. Physically, the pneumograph is one of several 3/8 x 5/8 x 7/8 inches modules incorporated in a miniature biotelemetry system, with separate modules being utilized to process signals derived from a number of physiological parameters such as EEG and EKG in addition to respiration. Considerable experimentation was performed regarding optimization of the electrodes used in this impedance pneumograph as well as the frequency and amplitude of the excitation voltage applied between the electrodes. The result was a fairly simple and inexpensive device which uses a higher frequency (300 KHz) excitation voltage than is normally used in impedance pneumography. The two electrodes, constructed of silver coated nylon for flexibility, are insulated from the subject by a layer of polyethylene film, thus forming a capacitive coupling of the electrode to the subject. This technique effectively eliminates changes in skin-to-electrode resistance, largely responsible for baseline drift encountered with previous impedance systems, so that this pneumograph responds only to variations in the actual impedance between the two electrodes. Empirically, a nearly perfect linear correlation was found to exist between the transthoracic impedance measured by this impedance pneumograph and pulmonary volume. The two insulated electrodes are pasteless and therefore easily applicable and non-irritating. They are held in position by an elastic, quick-donning, vest-like garment.
    • 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.
    • 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.
    • UHF Telemetry System Development at White Sands Missile Range

      Chin, Ball; White Sands Missile Range (International Foundation for Telemetering, 1967-10)
      This paper describes UHF telemetry system development at White Sands Missile Range (WSMR), New Mexico, to achieve the telemetry operation change from VHF to UBF. Component and subsystem development is discussed. Results of the S-band equipment testing using the L-20 light aircraft, the F-100F jet fighter, POGO missile, and ATHENA re-entry vehicles are presented. Comparative analysis of missileborne telemetry data transmitted through both the standard VHF and the developmental S-band links are made.
    • Description of Computer Program to Analyze Gain Distribution of an Antenna Pattern

      McQuaid, Bruce L.; Hughes Aircraft Company (International Foundation for Telemetering, 1967-10)
      The gain of a radiating antenna is generally a function of the direction in which the antenna is pointing relative to the direction of the received or transmitted signal. The gain distribution over an imaginary sphere surrounding the antenna is called the antenna gain pattern and can be measured experimentally. Under certain circumstances the tolerances associated with the pointing vector make it impossible to determine the antenna gain precisely but rather circumscribe an area on the spherical surface which include a number of different gain values. A computer program called INTGRT has been developed that will determine from measured antenna pattern data the gain distribution within the uncertainty region and will provide a measure of the probability of the gain being above a certain gain value. The boundary of the uncertainty region is described in terms of the coordinate system used in measuring the antenna patterns. Each gain value contained inside this boundary is compared to some reference gain level and a running total is made of the number of values found to be equal to or greater than the reference value and the total number of values inside the region. After weighting each total by an equal area function, the ratio of the number of values above a reference level to the total number of values in the region gives an estimate of the probability that the gain of the antenna will be equal to or above the reference gain. If the region is analyzed in this way for a number of reference levels, the distribution of gain values within the region is obtained. This information is extremely valuable in determining space communication system performance during periods in which the orientation of the spacecraft's antenna with respect to the earth cannot be determined precisely but is known to be within certain limits.
    • 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.
    • 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.
    • Detection of Orthogonal Sine and Cosine Pulses by Linear Active RC-Networks

      Schmid, P. E., Jr.; Nowak, D. J.; Harmuth, H. F.; Allen-Bradley Co. (International Foundation for Telemetering, 1967-10)
      An active RC matched filter, particularly useful for phase-coherent, coded or uncoded, binary or non-binary communication channels, is described. One detector circuit performs the equivalent of two simultaneous cross-correlations, avoiding the need for electronic multipliers, reference wave generation and phase synchronization. For example, only I circuits are needed in a receiver that is required to detect the polarity or presence of an orthogonal set of I sine and I cosine pulses. In view of the circuits realizability with linear IC technologies, the sensitivities with respect to circuit component variations are analyzed in detail. The results of the sensitivity analysis are presented in graphical form. Experimental results confirm the predicted performance; i.e. Q-factors in excess of 4000 were obtained with small, general-purpose operational amplifiers.
    • 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.
    • 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%.
    • Theoretical and Experimental Error Rates of PCM Codes

      DeWitt, K. I.; Perez, P. E.; United Aircraft (International Foundation for Telemetering, 1967-10)
      As PCM increases In -use as a method of transmitting data, it is of greater importance to know exactly the probability with which each bit may be received accurately. While most engineers in the field are aware of the basic probability curve for PCM signals, very few are aware of what to expect under the many varied conditions of noise bandwidth, data bandwidth, code type, method of data regeneration and DC offset. These effects are clearly handled in this discussion. The effect of phase jitter, always present in any data regenerating device, is ignored in this presentation, and will ultimately add another element of degradation, particularly at the higher noise levels.
    • 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 Wide-Band Multichannel Transmission System for Use with 5 MHz Coaxial Land Lines

      McGarry, William P.; Data-Control Systems, Inc. (International Foundation for Telemetering, 1967-10)
      An increasing number of telemetry systems have considerable distance between receiving sites and main ground stations, resulting in a need for multichannel wide-band communications systems. An operational system is described which permits the wide-band DC to 120 kHz video or predetection IF 450 kHz ±150 kHz signals from six receivers to be transmitted over one land line to the remote ground station.
    • Automatic Real Time Data Quality Analysis

      Williard, Merwin W.; Symetrics Engineering (International Foundation for Telemetering, 1967-10)
      This paper deals with methods of detecting and displaying the quality of received telemetry data automatically and in real time. The most commonly used forms of telemetry multiplexing are considered in detail-with reference to application of the techniques to other similar forms of multiplexing. This paper is a result of a study -and hardware development which resulted in equipment now at Cape Kennedy and capable of detecting and displaying bit error rate on PCM telemetry, percentage of channel error on PAM and PDM telemetry and signal-to-noise ratio on FM/FM telemetry. The discussion -is oriented toward the theory of operation and techniques for automatic real time data quality analysis rather than toward the hardware. Methods of detecting and displaying the various data quality indicators is emphasized resulting in conclusions that in many instances relatively reliable data quality indications are possible in real time, but it must be realized that any indication of quality represents a review of conditions of the received signal over some finite averaging interval and thus no measurement can ever provide instantaneous quality indications.
    • A Multiple Format Stored Program Data Acquisition System

      Bauer, W. R.; Hodges, G. G., Jr.; Telemetry Systems Department (International Foundation for Telemetering, 1967-10)
      A multiple format telemetry system is described which is flexible enough to be adaptable to many applications. The system incorporates a flexible programmer that utilizes a non-destructive readout memory which operates in conjunction with an external index counter. Subcommutator addresses stored in memory are addressed partially by the index counter and partially by the format instruction. Multiple formats can be generated, limited only by the requirement that the sampling rates in a given format be binary multiples of the slowest sampling rate in that format. The advantage of this programmer lies in the flexibility accommodated, typically, with one or two read-only memory cycles. The remote acquisition units used in the system are flexible in that they can be configured to provide various combinations of low-level, high-level, and bi-level inputs. These units are designed primarily from two large scale integrated (LSI) metal-oxide-semiconductor (MOS) building blocks. One LSI circuit is a sequential multiplexer, which also functions as an analog-to-digital (A/D) converter; the other circuit is a 16- channel random access multiplexer.