• International Telemetering Conference Proceedings, Volume 04 (1968)

      International Foundation for Telemetering, 1968-10
    • A Double Sideband-Quadrature Carrier Multiplex Telemetry System

      Gutwein, Joseph M.; Annese, Jerald F.; ADCOM (International Foundation for Telemetering, 1968-10)
      A novel FDM telemetry technique was developed consisting of a double sideband-quadrature carrier multiplexing system (DSB-QCM). Each subchannel in the DSB-QCM system carries two completely overlapping DSB data signals, one double-sideband modulated on the subcarrier itself, and the other on a quadrature version of the subcarrier. Demodulation with cophasal and quadrature subcarriers enables simultaneous data extraction from each channel within acceptable distortion levels. The feasibility and practicability of such a DSB-QCM telemetry system is discussed in this paper. Crosstalk levels between the quadrature multiplexed channels were measured and guardband requirements between adjacent channels were assessed for a modem comprised of three pairs of DSB-QCM channels. Crosstalk levels between uniformly loaded DSB -QCM channels were below 2% and guardband requirements equivalent to conventional DSB systems were observed. The DSB-QCM performance was also examined as a function of input SNR with two competing subcarrier synchronization methods. Subcarrier synchronization by means of synthesized reference tones coherently derived from a single pilot was demonstrated to be superior in The presence of noise to a channel reference approach in which each data channel must synchronize its own subcarrier. The major conclusion from this investigation is that DSB-QCM/FM telemetry combines the advantages of both SSB/FM and DSB/FM by accommodating as many data channels as SSB/FM but with low distortion data processing and the dc data response characteristic of DSB/FM.
    • 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.
    • Results of the UHF Telemetry System R & D Flight Tests at White Sands Missile Range

      Chin, Ball; Hamilton, James W.; White Sands Missile Range (International Foundation for Telemetering, 1968-10)
      This paper describes results of UHF telemetry R&D tests conducted at White Sands Missile Range (WSMR), New Mexico. UHF telemetry problems, such as multipath and target scintillation, are discussed. Several recommendations which may improve the reliability of telemetry data transmission at UHF frequencies are made based on experience and data gained from many UHF telemetry tracking operations.
    • 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.
    • Presampling Filtering

      McRae, D. D.; Davis, R. C.; Radiation Incorporated (International Foundation for Telemetering, 1968-10)
      Sampled data systems often employ lumped-parameter lowpass filters both prior to and following the sampling operation. The purpose of these filters is to reduce the error between the input and output data waveforms. The present paper discusses the effect of presampling filters on the rms interpolation error for two types of sampled data systems and gives some thumb rules for choosing such filters. The two types of sampled data systems considered are: (1) one employing only zero-order hold interpolation, and (2) one employing zero-order hold followed by the best lowpass lumped-parameter interpolation filter. The resulting expressions for rms interpolation error for sampled data systems employing lumped-parameter filters from a detailed time domain analysis are given.
    • Miniature Current Discontinuity Device Antennas

      Bittner, Burt J.; Kaman Nuclear (International Foundation for Telemetering, 1968-10)
      Flush and semi-flush, Current Discontinuity2 antennas have been developed for VHF and UHF frequencies that exhibit good efficiency and minimum structural disturbance. Typical antennas are .02 wavelengths high, 1/8th inch at "L" band. An airborne, electronically steerable array for VHF, satellite applications is described.
    • 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.
    • 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.
    • Frequency Feed-Forward-An Open Loop Approach for Extending the Threshold and Linearity of FM Demodulators

      Pelchat, M. G.; Boor, S. B.; Radiation Incorporated (International Foundation for Telemetering, 1968-10)
      This paper describes Frequency Feed-Forward, an open-loop technique for lowering the FM threshold. The amount of threshold improvement with standard discriminators is discussed and experimental results with sinewave and gaussian modulation are given.
    • 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.
    • 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.
    • An Adaptive Airborne VHF/UHF Transmitter System

      Franke, E. B.; Trover, W. F.; Teledyne Telemetry Company (International Foundation for Telemetering, 1968-10)
      The impending 1970 change-over of telemetry RF links from VHF (215- 265 MHz) to UHF (1435-1545 and 2100-2200 MHz) requires a quantum jump in the state-of-the-art of solid-state transmitters. This problem is compounded by the fact that in certain instances, especially for spacecraft and special applications, there is still a need for transmitters at many different VHF and lower UHF frequencies between 136 MHz and 1 GHz. Therefore, the optimum RF product line is represented by a modular transmitter system composed of fundamental building blocks which will permit the assembly of transmitters capable of producing from 50 watts at 136 MHz to 1/2-watt at 5500 MHz with minimal variations in the over-all mechanical configuration. This adaptive transmitter system must also be able to provide optional features such as power-to-case ground isolation, modulation-to-power ground isolation, turn-on current limiting, either frequency of phase modulation remote turn-on capabilities, and internal telemetry functions of temperature, RF power, dc voltage. Additional design requirements for such a transmitter system are wideband frequency response and carrier deviation capabilities so that the transmitter may handle real-time video signal for use with television, radar and infra-red transmission systems. This paper describes the design alternatives and the conceptual approaches that were used in development of such an adaptive transmitter system. Performance data presented is typical of that achieved from L-band and S-band units.
    • 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.
    • 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.
    • Synthesis of High Data Rate Coherent Telemetry Systems

      Ma, L. N.; Stone, M. S.; Sullivan, D. P.; TRW Systems Group (International Foundation for Telemetering, 1968-10)
      For high data rate telemetry (above 100 Mbits/sec) multiphase modulation effectively trades transmitter power to alleviate the RF bandwidth requirements. This paper presents a unified method of synthesizing and analyzing multiphase systems. In particular, the design of multiphase modulators and three types of coherent demodulators are discussed in detail. Included is a description of 400 Mbits/sec quadriphase system fabricated by TRW which employs direct modulation and demodulation of an 8.5 GHz carrier and a transversal filter to effect matched data filtering. This system operates within 2.5 db of theoretical performance of coherent quadriphase.
    • The Effect of Coding on Rate Equalization of Digital Channels

      Butman, S.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1968-10)
      The pulse stuffing technique for rate equalization of digital channels is generalized in this article to the stuffing of a sequence of pulses (a word), which can be coded. The extra capacity needed for signaling the stuffed word decreases exponentially with the number of pulses in it, and may, in fact, be eliminated at a negligible increase in the error rate of the channel.
    • 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.
    • 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.
    • 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.