• 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.
    • 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.
    • 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.
    • 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.
    • Flight and Laboratory Testing of a Double Sideband FM Telemetry System

      Richardson, Robert B.; Harney, Paul F.; NASA Flight Research Center (International Foundation for Telemetering, 1968-10)
      This paper discusses the NASA Flight Research Center's laboratory and preliminary flight evaluation of a double sideband suppressed carrier constant-bandwidth telemetry system that will be used as an airborne high-frequency data recorder. Some practical limitations are illustrated, and laboratory and flight-test results are compared. No attempt is made to compare this system with systems using other forms of modulation. Results obtained using an RF link are compared with magnetic tape recording of data. Calibration requirements are included for each 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.
    • High Reliability Tape Recorders for Satellite, Aircraft & Drone Applications

      Wiig, Selmer; Santee, Robert; Lucas, E. D., Jr.; Borg-Warner Controls; Best Electronics (International Foundation for Telemetering, 1968-10)
      A new series of magnetic tape recorders has been developed and flight tested, offering a much higher reliability figure and somewhat improved performance over previous design, especially in terms of long life. Featured is a transport design having only seven moving parts, as compared with three or four times that many in conventional tape recorder mechanisms. Details of this design are described indicating how it is possible to achieve an operating life of 16,000 hours of continuous service in satellite applications. A comparable electronic advance has been in digital record-reproduce techniques where Borg-Warner Controls engineers have developed bit dejittering and servo speed control circuitry that makes possible transmission of recorded PCM or other digital data at high data rates with an essentially jitter-free output from reproducer to telemetry transmitter.
    • A High-Rate Telemetry System for the Mariner 1969 Mission

      Tausworthe, R. C.; Easterline, M. F.; Spear, A. J.; California Institute of Technology (International Foundation for Telemetering, 1968-10)
      This presentation deals with a multi-mission deep-space telemetry system, its rationale, analysis, development into hardware, and its subsequent planned application to an actual spacecraft mission whose preparation is now in progress. The spacecraft system encodes raw binary data into a comma-free, bi-orthogonal code which antipodally modulates a square-wave subcarrier, which in turn phase-modulates the downlink carrier. There is no separate signal for subcarrier, word, or symbol sync; all transmitted sideband power is thus available for data transmission.
    • International Telemetering Conference Proceedings, Volume 04 (1968)

      International Foundation for Telemetering, 1968-10
    • 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.