• Performance of Block-Coding Systems When Transmitting Through a Ary Discrete Channel in the Presence of White Gaussian Noise

      Okkes, R. W.; European Space Technology Centre (International Foundation for Telemetering, 1968-10)
      The basic problem of transmitting digital (PCM) data with the least signal to noise ratio per bit of information is considered if the data is encoded into code words consisting of a finite number of symbols where each symbol belongs to an alphabet of N elements. For quantitative results the error probability of the decoded data has been taken as equal to or below one out of 10⁵ bits of information in the case where the transmitted symbols are corrupted by additive white Gaussian noise and are detected "symbol per symbol" by correlation methods. Mainly coherent detection is considered. After the derivation by a geometrical method of the upper bounds (based upon random coding) of the minimum signal to noise ratio per bit, the performance of several constructive code methods are compared with these bounds. The amount of hardware and the number of operations required respectively for encoding and for decoding the most promising class of codes (binary and N-ary Bose-Chaudhuri codes) are indicated. Considerations are given to synchronous demodulation requirements using a "Costas" phase lock loop type of demodulator.
    • Wideband PCM-FM Bit Error Probability Using Discriminator Detection

      Hayes, J. J.; Chen, C. H.; Kubicki, W. J.; AVCO Corp.-MSD (International Foundation for Telemetering, 1968-10)
      The expression for bit probability of PCM/FM is derived for a receiver with an IF bandwidth equal to or greater than the data rate, limiter-discriminator detection; followed by a post-detection filter with bandwidth equal to the data rate. The optimum deviation ratio is shown to be essentially constant regardless of the IF bandwidth-to-data rate ratio and system performance is shown to degrade when this ratio is greater than unity. Pre-modulation filtering of the transmitted PCM data is experimentally tested and the analytical results are shown to good agreement with experimental data.
    • Preliminary Experiment Results from the Omega Position Location Equipment (OPLE)

      Horiuchi, H. S.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1968-10)
      The analysis of data taken during the fixed platform, road and aircraft tests indicates that the OPLE system can locate a fixed or moving platform with reasonable accuracy. During the fixed platform interrogations, it was found that the error in the OPLE-derived position estimates were consistently correlated with the error in the position estimates of the OCC as derived from the local Omega monitors; that is, latitude and longitude errors of corresponding magnitudes were received at the OCC both from the PEP's and from the Omega receiver located at the control center. Based on the data analyzed thus far for the fixed platforms, the overall contribution to the mean position error by the OPLE equipment ranges between 50 to 400 feet in latitude and 300 to 500 feet in longitude. The results have shown that the longitude errors are consistently greater than the latitude errors. The results of the road test indicated that a moving vehicle could be located with good accuracy. Men the OPLE-derived position estimates were adjusted for the navigational errors of the Omega system, the vehicle was located to within 1500 feet of the roadway. The results of the aircraft tests showed that an airborne platform moving at 160 knots could be located with reasonably good accuracy. During the daytime test, the position of the aircraft could be placed to within approximately 5 miles of GSFC. During the evening tests, the position of the aircraft was located to within 10 miles of the estimated center of the aircraft's circular flight pattern, the position being consistently to the east of the center of the circle. During these evening tests, the position of the OCC was calculated to be 4 miles east of its actual location.
    • Expected Number of Spikes of Phase Locked Loop Demodulators

      Osborne, P. W.; Schilling, D. L.; Polytechnic Institute of Brooklyn (International Foundation for Telemetering, 1968-10)
      A new method is presented for finding the expected number of spikes in a phase locked loop of any order, with or without modulation. The procedure can also be employed to determine the threshold of FMFB, FM discriminators and the Maximum Likelihood Estimator. The low pass equivalent gaussian noises x(t), y(t) in the differential equation describing the system (PLL or FMFB) are replaced by the deterministic time functions (Conditional Expectations) 1) E[x(t)/x(0), ẋ(0)] 2) E[y(t)/y(0), ẏ(0)] and solved on a digital computer. The mid spike time (t=0)is taken to be the time when x(0) (quadrature noise)=0, and a surface or surfaces in ẋ(0), y(0), ẏ(0) space are determined which indicates the region A where spikes in the demodulator are obtained. From this the expected number of spikes per second is calculated. Results are presented for the first, second, and third order phase locked loops, and for an ordinary FM discriminator (which can be shown to be equivalent to a PLL of infinite gain). The second order loop used a constant plus integral filter, while the third order loop used a constant plus integral plus double integral filter.
    • International Telemetering Conference Proceedings, Volume 04 (1968)

      International Foundation for Telemetering, 1968-10
    • Single RF Carrier Time-Sharing by Remote Locations

      Stadler, S. L.; United Aircraft Corporation (International Foundation for Telemetering, 1968-10)
      It is of vital national interest to know the essential real-time factors involved in the evaluation of an air attack versus a ground defense. This need led military planners to request the development of a computerized system to determine the victors and the vanquished in a war game on a par with an actual combat situation. From an engineering point of view, the evaluation system would permit all "combatants" full scope of operation and would not introduce, of itself, any "artificialities" into a complexity of split-second duels taking place over a wide geographical area. This paper discusses a unique time-division telemetry technique that was designed to resolve the data and control flow to and from remote locations, in this case, tactical aircraft. The actual system that evolved from this approach transfers all "aim and fire" events, coming from a group of aircraft engaged on a "mission", to a central communications and data processing facility. The control in the form of timing synchronization is sent from the facility to all aircraft. It should be noted that this time-sharing method could not utilize classical time-division multiplexing, e.g., PAM or PDM, since the test elements were all physically separate from one another (up to 120 miles). Preliminary test data is presented herein as an indication of the validity of this new technique. The paper concludes with a brief description of this method as applied to air and water pollution control and other posited applications.
    • Cracked Solder Joint Mechanism in Discrene Component Assemblies

      Estes, H. P.; Theobald, P. E. (International Foundation for Telemetering, 1968-10)
      Solder joint cracking has occurred in assemblies where discrete part subassemblies are fabricated on Printed Circuit Boards and conformal coating is applied to the sub-assembly. The objective of the investigation were to determine the extent and seriousness of the problem, to determine the cracking mechanism, and to provide engineering and process information to eliminate the problem. The analysis and test results indicate that many factors influence the strength of a solder joint and the ultimate crack that develops. Contamination by gold products and other foreign materials can significantly affect solder characteristics. Aging and temperatures experienced in the normal operating range of certain equipment adversely affects the strength of the solder materials. Conformal coating between the discrete part and the Printed Circuit Board is a major contributor to the cracking mechanism. Transistor assemblies using a Spacer under the TO-5 enclosure with Kovar Lead Material and completely covered with conformal coating have a high incidence of cracked solder joints. This condition is caused by the mis-match of coefficients of expansion between the Kovar Lead and the conformal coating.
    • A Two-Channel Monopulse Telemetry and Tracking Antenna Feed

      Yaminy, R. R.; Radiation Systems, Inc. (International Foundation for Telemetering, 1968-10)
      The two-channel monopulse telemetry and tracking antenna feed operates over the frequency range from 1435 to 2300 MHz. The feed was designed and developed for a 7-foot parabolic reflector located in the nose cone of an EC-135N aircraft. This airborne system maintains in-flight voice and telemetry communications with Apollo spacecraft during the injection and reentry phases of the Apollo missions. The feed consists of a planar multimode dual-polarized cavity-backed spiral radiator and two printed circuit comparators. The spiral radiator is excited in the sum and difference modes at both its inner and outer filament terminals. This allows the simultaneous reception of right-hand and lefthand circularly polarized signals. The sum and difference modes of excitation are precisely controlled to provide the proper reflector illumination functions for improved sidelobes and efficiency. Sidelobe levels in excess of 22 db, null depths greater than 40 db, boresight shifts of less than 0.25 degree, and system efficiencies of greater than 40 percent have been achieved.
    • Design of Airborne S-Band Telemetry Antennas

      Weinschel, H. D.; New Mexico State University (International Foundation for Telemetering, 1968-10)
      The change from VHF to UHF for telemetry requires new antenna designs rather than the scaling of the antennas now used for the UHF frequencies. The reason for this is that the vehicle dimensions at UHF, in particular the rocket diameters, will be of the order of several wavelengths. A common method to obtain a nearly omnidirectional radiation pattern at VHF is to mount two or four element antenna arrays on the vehicle. This is sufficient since the wavelength for the presently used telemetry frequencies is approximately 50 inches and the array spacing rarely exceeds a half wavelength. The radiation pattern from such closely spaced unit radiators exhibits only minor scalloping which does not present a problem in the data acquisition. At the UHF frequencies, the array spacing, in wavelength, is increased by a factor of ten resulting in an interference pattern with narrow lobes and deep nulls. If the mechanical design limitations permit it, it is possible to design unit radiators which will give cardioid or nearly omnidirectional patterns for a single polarization component. Two such antennas are described. They are the axially mounted turnstile and the radial waveguide antennas.
    • Optimum and Sub-optimum Detection of Digital Sequences Corrupted by White Noise

      Holmes, J. K.; Butman, S.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1968-10)
      This paper presents an optimum and a sub-optimum, but easily recognizable, method for the detection of K binary symbols corrupted by white Gaussian noise with unknown mean. Basically the optimum procedure requires picking the sequence from a set of 2ᴷ sequences which minimizes a certain functional. However this procedure requires a great deal of computation. This computational problem is considerably reduced by the use of an efficient searching procedure developed in this paper. However a sub-optimum procedure exists and is very simple to instrument with the advantage that decisions are made in a bit-by-bit fashion. This procedure is analyzed and the average error probability is obtained.
    • Digital-Data Transition Tracking Loops

      Lindsey, W. C.; Anderson, T. O.; University of Southern California; Jet Propulsion Laboratory (International Foundation for Telemetering, 1968-10)
      This paper is devoted to the problem of tracking data-transitions in digital communication systems by means of decision-directed phase-tracking loops. Such techniques are of interest because these methods provide the receiver with a knowledge of the time instants when the modulation may change states without using the additional transmitter power. The results presented are useful in designing synchronizing circuitry for a wide variety of digital systems. One particular system mechanization plan is presented.
    • Multifunciton Receiver System for Integrated Tracking, Telemetry and Ranging Data Acquisition

      Shaffer, H. W.; King, E. L.; NASA/Goddard Space Flight Center; General Dynamics Corporation (International Foundation for Telemetering, 1968-10)
      The state-of-the-art for Tracking, Telemetry and Ranging data acquisition has reached a point where simultaneous performance of each of these functions is possible with one receiving system. In addition to simultaneous reception of data with one receiver, this Multifunction Receiver System was developed to be compatible with the other DOD and NASA Tracking and Data Acquisition systems besides the specific system for which it was designed, the Goddard Range and Range Rate System. NASA/Goddard Space Flight Center initiated development of this integrated receiver system in September 1967 and will have the first system operational in December 1968 at Rosma4, North Carolina. Three more systems will be installed: one each at NASA STADAN stations in Alaska, Tananarive, and Carnarvon, Australia. The receiver system was designed to cover all the currently known NASA and DOD frequency bands from VHF to 10 GHz. The data handling capability of the system is optimized for both narrowband and wideband data. AM, FM and PM data is accommodated in varying bandwidths from 10 kHz to 10 MHz. The primary objectives for developing such a system were to achieve improved mission effectiveness of NASA STADAN operations and reduce life-cycle costs in carrying out NASA Tracking and Data Acquisition responsibilities.
    • A Data Recording System for Deep Sea Logging

      Ben-Yaakov, S.; UCLA (International Foundation for Telemetering, 1968-10)
      A data recording-reproducing system has been developed in conjunction with an oceanographic in situ multi-sensor probe for measuring chemical properties. The recording unit is built around a deck of a single channel, entertainment-type miniature magnetic tape recorder. The tape speed was reduced to 0.125 ips by slightly modifying the original speed control, which results in four hours' continuous recording. The recording unit incorporates a frequency counter to convert the input frequency signal to a serial, four digits, BCD code. The code is recorded twice per frame by chopping the bits with a 250 Hz signal. The frame lasts 5 seconds after which a command is sent to the main unit advancing the multiplexer one step ahead. The reading unit consists of a second small tape recorder and a decoding circuit. The tape is played back 15 times faster than the recording speed. Synchronization and bits identification are based on counting the (original) 250 Hz chopping signal. This eliminates the problem due to wow flutter and non constancy of tape speeds. The serial BCD code is converted to a parallel code to facilitate printing or tape-to-tape transfer, for computer compatibility. The use of non-expensive tape decks as well as integrated circuit modules reduces markedly the price of the system without compromising on accuracy or reliability.
    • Performance of Binary PSK Communication Systems

      Oberst, J. F.; Schilling, D. L.; Polytechnic Institute of Brooklyn (International Foundation for Telemetering, 1968-10)
      The degree of RF coherence which can be established between transmitter and receiver greatly influences the performance of binary communication systems. Practical systems are partially coherent; the main classes are transmitted reference (TR) and single channel (SC). Although SC systems are potentially superior, they are difficult to analyze and have an inherent mark-space ambiguity problem. In this paper, four SC PSK systems have been studied using Monte Carlo simulation on an IBM 360/50 digital computer. Differential data encoding was used. The systems investigated include Decision Feedback (DF), Squaring (SQ), and a variation of SQ called Absolute Value (AB). In addition, a new Maximum Likelihood (ML) SC system, which is optimum in a restricted sense, is derived and simulated. The simulation results show that all of these systems yield comparable average probability of error. This is in contrast with results which have been published previously. Furthermore, the systems can all be shown to reduce to Differential PSK when the number of reference bauds is one. Finally, a method is introduced for studying the effects of various methods of data encoding on SC system operation.
    • The Effects, Measurement, and Analysis of Flutter in Instrumentation Recorders

      Moore, Laurence; Micom, Inc. (International Foundation for Telemetering, 1968-10)
      As instrumentation recorders are improved to provide wider bandwidths and shorter recorded wavelengths, the effects of flutter and attendant time base distortion severely limit the potential for accurate recording and retrieval of data. The effects of flutter on typical classes of data is given and the measures necessary to determine flutter with high accuracy shown. Since the degrading effects of flutter depend upon the application and the characteristics of the flutter, means of analyzing flutter both in the time domain and in the frequency domain are necessary. A self contained instrument for accurate measurement and analysis of flutter sensitive enough for the most sophisticated transports is described, as are necessary conditions for its use.
    • Buoy Telemetry for Environment Prediction in Fisheries Research

      McAlister, W. Bruce; Bureau of Commercial Fisheries Biological Laboratory (International Foundation for Telemetering, 1968-10)
      A telemetering buoy has been developed for the Bureau of Commercial Fisheries to provide environmental information in support of salmon research. The buoys are designed to be free-drifting units; sensors are inductively coupled to a 200 m. single conductor cable beneath the buoy. Present sensors measure temperature, conductivity and depth. One buoy is equipped to participate in the IRLS satellite telemetry experiment. Present development includes equipment to have the buoys determine their position by use of the U.S. Navy Navigation Satellite System.
    • Errors Resulting from Channel Filters and Adjacent Channel Crosstalk in DSB/SC Telemetry Systems

      Salter, W. E.; Frost, W. O.; Sperry-Rand Corporation; Marshall Space Flight Center (International Foundation for Telemetering, 1968-10)
      The waveform distortion resulting from adjacent channel crosstalk and from amplitude and phase nonlinearity in channel filters limits the minimum channel spacing, and hence the bandwidth utilization efficiency of a double sideband/suppressed carrier (DSB/SC) telemetry link. The paper presents results of an analysis defining the minimum achievable mean-square error when Butterworth filters are used in the DSB demodulator/demultiplexer. With data inputs consisting of band-limited random signals, solutions are given for various combinations of data order, filter order, channel spacing, and filter cut-off. The trade-off between waveform distortion and channel spacing is illustrated, and optimum locations for the filter cut-off are defined. The irremovable error based on Weiner optimum filter theory is presented as an interesting basis for comparison.
    • Communications Between Satellite and Ballons for the Eole Mission

      Bourdeau, J. P.; Debray, P.; Namy, X.; CNES (International Foundation for Telemetering, 1968-10)
    • The Sun as a Calibration Signal Source for L- and S-Band Telemetry

      Hedeman, W. R., Jr.; Aerospace Corporation (International Foundation for Telemetering, 1968-10)
      One of the major problems confronting a telemetry receiving station is that of self calibration, particularly an end-to-end calibration, on a frequent and routine basis. For this purpose an external signal source is needed, preferably one in the far field of the antenna. The sun is such a source for L- and S-band systems--its usefulness depends on knowledge of its emission at the time it is used, since it is a variable source. Examined here are the characteristics of the sun as a source of electromagnetic energy in the 10 centimeter region, and the methods by which it could be used to determine receiving system noise temperature. Limitations of the methods are also described.
    • Miniature Power Amplifier for Telemetry Transmitters

      Winkler, R. H.; Amelco Semiconductor (International Foundation for Telemetering, 1968-10)
      There is continuing emphasis to reduce the size and weight of telemetry transmitters and to increase the frequency at which the power is generated. An approach to achieve this goal is discussed. A power amplifier stage designed specifically for a telemetry transmitter is described. It produces 1 watt output at 500 MHz with 7-10 db of gain. Typically it is midpoint in a series of similar amplifier stages. An extraordinarily small size is achieved by using microstrip transmission lines on an alumina substrate. The dielectric constant of alumina is relatively high; which makes the transmission lines relatively short. Furthermore, the judicious use of lumped capacitors results in a further foreshortening of the transmission lines. The transistor die is attached directly to the microstrip transmission line. This minimizes any stray inductances and makes the circuit reproducible and broadband. This amplifier is composed of three basic component types: 1) a transistor 2) four microstrip transmission lines, and 3) three lumped capacitors. Of special importance is the fact that the entire amplifier, that is, the transistor plus the matching network, is enclosed inside a hermetic envelope. The terminals are 50 ohm microstrip input and output. The hermetic envelope is less than 1.100" x .830" x .085". Complete with a heat sink the unit is no higher than .150". Useful design information for this type of amplifier is presented.