• Laser Applications to Biology and Medicine

      Rounds, Donald E.; Pasadena Foundation for Medical Research (International Foundation for Telemetering, 1968-10)
      The unique physical characteristics of coherence, intensity, and monochromatically offered by laser instrumentation has placed renewed importance on studies in photochemistry and photobiology. Sufficient research experience has now been accumulated to demonstrate the potential usefulness of laser energy to fundamental cell biology, and to the diagnosis and treatment of certain pathological conditions. Current progress in laser applications to ophthalmology, oncology, and dentistry is briefly summarized.
    • A Maximum Likelihood Bit Synchronizer

      Mallory, P.; Dynatronics (International Foundation for Telemetering, 1968-10)
      A method of implementing a maximum likelihood synchronizer for baseband signals in Gaussian noise is presented along with analysis and measurements of its noise performance. Results are given showing the noise jitter of the synchronizer as a function of the energy per bit to noise power density ratio for various parameters of the synchronizer system. The Cramer Rao inequality is used to give a qualitative description of the system noise performance in terms of the signal structure. Finally the noise performance of this technique is compared with several other techniques which are currently used to synchronize baseband PCM signals.
    • 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.
    • 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.
    • 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.
    • 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.
    • Output SNR of an FM Discriminator with Non-Ideal Limiting

      Schilling, D. L.; Refi, J. J.; Polytechnic Institute of Brooklyn; Bell Telephone Laboratories (International Foundation for Telemetering, 1968-10)
      The effect of abrupt-limiting on the output of a frequency discriminator has been treated thoroughly by Middleton. This paper considers the case of smooth band-pass limiting both for the simple differentiator and for the balanced discriminator. The error function is used as a model for the smooth limiter. The idealness of the limiter is related to the quantity "μ" - the limiting hardness. The analysis reveals that for a balanced discriminator, the output signal-to-noise ratio can be made largely immune to changes in "μ". However, for the unbalanced discriminator, the signal-to-noise is not only appreciably "μ" dependent, but also a function of carrier frequency.
    • A PCM-Telemetry System for Sounding Rock Payloads

      Hommel, R.; Deutsche Versuchsanstalt für Luft- und Raumfahrt e.V. (International Foundation for Telemetering, 1968-10)
      Complex sounding rocket payloads require on-board data processing and channel capacity which frequently exceed the capability of the standard FM-FM-telemetry system. To obtain the full benefit of the accuracy and information density of sounding rocket experiments a PCM-telemetry system has been developed which provides sufficient flexibility in the choice of channel number, bit rate, time resolution, and accuracy. A first version with Bo channels for scientific data, and 62 channels for technical data will be flown on board of five Black Brants from the Esrange in Kiruna.
    • Performance Characteristics and Specification of PCM Bit Synchronizer/Signal Conditioners

      Peavey, B.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1968-10)
      The PCM BR Synchronizer/Signal Conditioner, hereafter called "synchronizer," plays a vital role in telemetry data recovery, and is perhaps the most important and complex component of telemetry data processing systems (DPS). The synchronizer, being the "front end" of the system, makes an irrevocable decision as to the binary value of each data bit, and provides the fundamental timing signal (clock) for the entire DPS. Thus, the performance characteristics of the synchronizer substantially determine the system's capabilities, and it may be said that the system is as good (or bad) as the synchronizer. This paper presents and discusses test data obtained on synchronizers available to date, and used at Goddard Space Flight Center (GSFC) and its satellite tracking and data acquisition network (STADAN) stations. Performance characteristics such as bit synchronization (bit sync), bit sync acquisition, tracking, bit error rate, and intersymbol interference have been measured with respect to split-phase (SP) and NRZ-L input signals between 500 bps and 300 Kbps, perturbed by "white" Gaussian noise plus jitter. The effect of tape recording and band limiting of these signals on synchronizer performance is also discussed. It is shown that bit error rate alone does not "tell the whole story" about synchronizers, particularly when operating with low (less than 7 dB) SNR's plus jitter. The test data indicate that there is no single synchronizer excelling in all respects. For example, a synchronizer which operates well down to SNR of -3 dB has inferior acquisition, and slippage characteristics when jitter is added to noise. Generally, the performance threshold for random jitter (defined later) is at SNR greater than 10 dB. Some synchronizers seem to perform better with SP than NRZ-L signals, and vice versa. Finally, discussed and suggested are definitions of performance parameters which would uniformly and unambiguously describe and specify synchronizers. A lack of precisely defined and measurable performance parameters and characteristics has caused misinterpretation and misunderstanding of specifications presented by both vendor and customer.
    • Performance of a Bandwidth Limited PCM/PSK/PM Telemetry System

      Miller, G. E.; Jennings, V. A.; The Boeing Company (International Foundation for Telemetering, 1968-10)
      This report investigates the use of coherent and non-coherent FM/PM detectors as applied to recovery of PCM telemetry data. Given a PCM Manchester II encoded FM carrier, a theoretically perfect bit detector was derived. A laboratory prototype was built and evaluated under simulated threshold conditions. Agreement with theory was obtained within 1.50 db, using a coherent demodulator without a limiter stage. Amplitude and phase characteristics are shown in addition to the filter circuit and component values. Several commercial demodulators are compared against the theoretical model. The results of the comparisons are discussed, and recommendations concerning deficient areas are submitted.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • RF Telemetry from a High Speed Subterrain

      Caffey, T. W. H.; Hale, W. R.; Sandia Corporation (International Foundation for Telemetering, 1968-10)
      The telemetry of the deceleration loading upon a vehicle which deeply penetrates the earth at high speeds is described. The technique consists of using a single-channel, narrow-band FM transmitter to drive a magnetic dipole so that RF communication with above-ground receivers is provided. A 260-kHz, 340-watt system with a 2-kHz bandwidth is described along with design considerations. The reduction of the conductivity along the signal path by the penetration tunnel with consequent signal enhancement is discussed.
    • Rician Intersymbol Interference in Frequency Shift Keying

      Vencill, J. J.; McDonnell Douglas Astronautics Company (International Foundation for Telemetering, 1968-10)
      Many communications links involve a reflected signal which is Rician in nature. In troposcatter systems, this reflection constitutes the entire received signal while in communications between satellites or aircraft, such a reflection from the surface corrupts the direct signal. Other such situations involve low elevation tracking or intentional coherent jamming. This paper derives the bit error probability for a non-coherent binary FSK link in this environment for any order of diversity and any ratio of specular to diffuse reflection assuming orthogonal signalling frequencies, matched filter detection and perfect bit synchronization. The interfering signal may represent the same datum as the direct signal (Mark-Mark interference) or, for delays longer than a bit period, the interference may appear in the opposite receiver channel from the direct signal (Mark-Space interference). Results are stated in terms of the direct signal energy to noise density ratio and factors determined by the geometry of the situation; the ratio of direct signal to interfering power, the ratio of specular to diffuse reflected power and the relative carrier phases of the direct signal and the specular reflection in the Mark-Mark case. These geometric parameters are most conveniently treated separately from the modulation and detection problem.
    • The Signal-to-Noise Ratio Estimation Techniques for PCM Signals

      Sos, John Y.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1968-10)
      Reliable estimation of signal-to-noise (S/N) ratio in a demodulated PCM telemetry signal can be useful in evaluating the performance of the complete telemetry link, including its signal detection and data processing portions. This paper describes three potentially practical methods developed at Goddard Space Flight Center for estimating the S/N ratio in a PCM signal. One method referred to as "spectral null" method uses spectral characteristics of PCM' signals to estimate the S/N ratio, the other two use statistical properties of the signal, i.e., its mean value and variance. These two methods are known as "variance estimations and "null zone." The implementation of each method is discussed. The spectral null method takes the least amount of equipment, but is more difficult to calibrate and operate over a wide range of bit rates, than the other two systems. All three approaches, however, are uncomplicated enough to be included into almost any existing PCM data handling system. An analysis of the performance characteristics of each system is made. It is shown that the variance estimation method is the most versatile. It can reliably estimate the S/N ratio to within 1.5 db over a range of S/N ratios from 0 db to +10 db. (The S/N ratio is defined as the ratio of signal energy per bit/noise power density.) Under certain conditions all three methods can provide estimates to within 1 db, especially over a S/N ratio range from +3 db to +10 db.
    • 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.
    • The Small Astronomy Satellite (SAS) Program

      Townsend, Marjorie R.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1968-10)
      One of NASA's newest Explorer class satellite programs, the Small Astronomy Satellite (SAS), will provide much-needed information in the most recently studied fields of astronomy, X-ray, Gamma-ray, UV and IR. This paper will describe the basic spacecraft functions with emphasis on its key feature, the SAS control system, as proposed for early sky surveys, and the changes needed in it for later flights which will require a pointing capability of one arc-minute or better. Its flexibility and versatility for application to many different types of astronomy experiments will be examined.