RSS 1.0International Telemetering Conference Proceedings, Volume 05 (1969)
ABOUT THE COLLECTION
The International Telemetering Conference/USA (ITC/USA) is dedicated to the promotion and stimulation of technical growth in telemetering and its allied arts and sciences. It is the premier annual forum and technical exhibition providing telemetry specific short courses, technical papers from professionals and students, and exhibits of the industry’s leading companies. ITC/USA is sponsored by the International Foundation for Telemetering (IFT), a non-profit corporation dedicated to serving the technical and professional interests of the telemetering community.
This collection contains the proceedings of the fifth International Telemetering Conference, September 15-17, 1969. The conference, sponsored by the International Foundation for Telemetering, was held at the Sheraton Park Hotel in Washington, D.C.
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International Telemetering Conference Proceedings, Volume 05 (1969)International Foundation for Telemetering, 1969-09
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Telemetry-Scoring ReceiversIn order to provide high accuracy telemetry and miss distance data in the 2200-2290 MHz band, improved receiver sensitivity and exceptional frequency stability are required. The higher receiver sensitivity is required due to extended range requirements with an antenna as small as possible. The exceptionally high frequency stability arises from the fact that typical deviations in center frequency during an intercept is in the order of a few KHz out of 2250 MHz. If the frequency stability problem is not handled properly, this information can be distorted to the point of uselessness. Another problem area that arises as a by-product of stability is phase noise in the local oscillators that degrade the output SNR of a quieted receiver. The solutions to such problems are described in the following sections along with the compromises required for operation on board ship.
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A Phase-Locked UHF Telemetry Transponder for Missile Scoring ApplicationsThe Phase-Locked UHF Telemetry Transponder described in this article is part of the recently conceived Cooperative-Doppler Missile Scoring System. This system obtains the doppler curve of a missile relative to its target, without the use of special scoring equipment in the missile. This is accomplished through comparison of the telemetry information from the missile with a transponded signal from the target aircraft. The transponder is housed in the target aircraft and is responsible for transponding PAM/FM modulation from the telemetry band (2200-2290 MHz) to the scoring band (1760-1850 MHz), while preserving the phase of the modulation during the frequency translation. In order to accomplish this, true phase demodulation of the PAM/FM signal has been achieved through utilization, of the phase-lock technique. Included in this article is an analytical discussion of the phase-lock loop design with derivations of the closed-loop transfer function and response bandwidth; Root-Locus analysis; Bode diagram; and dynamic range and phase response considerations.
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Frequency Diversity for UHF TelemetryThis paper describes the function and design of the CV-2138 (XAN-1) UHF Down Converter developed at the Naval Avionics Facility, Indianapolis, Indiana. This unit is part of the Navy's Tartar, Terrier, Talos missile UHF telemetry/miss-distance information (MDI) system AN/SKQ-2 (XAN-1) now under development at this Facility. The converter, a dual-channel unit, receives signals in the 2200-2290 MHz and 1760-to-1850 MHz bands, and produces IF's of 240-330 MHz and 110-200 MHz respectively. The 1960 MHz local oscillator (LO) frequency, common to both channels, is supplied from a single source.
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Frequency Diversity for UHF TelemetryThe use of frequency diversity to allow substantial airborne antenna simplification for L and S band telemetry is described. The system is particularly useful on large, spin stabilized vehicles where omni-directional antenna coverage is required. Typical antenna patterns with and without diversity are presented. A systems block diagram showing dual receivers and diversity combiner is also described. A weight tradeoff is presented for diversity versus non-diversity, with vehicle diameter (at the antenna location) as the variable. It is shown that, at S band, for diameters in excess of about 5 in., frequency diversity represents a favorable approach.
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Digital Time-Base Error Compensator for Wideband Telemetry Recorder/ReproducersAn advanced development model of a telemetry predetection recording error compensator was designed to reduce flutter and time displacement errors in magnetic tape instrumentation recorder/reproducers so that the final intra-channel timebase error (TBE) does not exceed ±0.1 μsec. The device will operate with recorder/reproducers having bandwidths up to 1.5 MHz and as much as a millisecond of TBE. The incoming waveform is sampled, digitized, and stored in a memory on a recorded pilot tone at a rate determined by the flutter, using phase-lock techniques. Subsequent readout of the memory, composed of MOS shift registers, at a synchronous rate, produces a replica of the playback waveform with wow, flutter, and TBE significantly reduced. This technique offers the following advantages over other approaches: direct delay/BW trade-off (i.e. , 1 msec TBE correction at 120 ips, 2 msec TBE correction at 60 ips, etc.), small size, lightweight, low power requirements, and extensive use of MOS and IC devices, amenable to future LSI construction.
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UHF TM System Coverage Predictions Over WaterA portable telemetry receiving station was desired for use in testing a family medium range surface-to-air missiles. It was recognized that the crucial item in a lightweight portable telemetry system at this time is the telemetry receiving antenna. This is a result of the following facts: (1) the amount of transmitter power available from the missile at UHF is limited due to component capability, (2) the amount of power radiated by the missile in a given direction varies widely due to missile antenna pattern lobing, (3) the beam of the receiving antenna is narrow and the antenna size is correspondingly large if the antenna is designed to have sufficient gain to compensate for the reduced dipole aperture at UHF , and (4) the increase in performance possible by reduction of system noise figure is both expensive to obtain and difficult to justify in a noisy shipboard RF environment. An analysis was made of the portable telemetry system including the shipboard antenna and RF path in order to predict the range of coverage as various system parameters differ. This paper details some of the results of this system coverage analysis.
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The High Speed Tape TransportThe Newell tape transport principle is used in instrumentation recorders to currently provide upwards of 56 minutes of recording with 15 MHz bandwidth. Bandwidth several times as wide are definitely feasible. The main characteristic of the tape transport is that it permits precise tape handling at speeds up to several thousand inches per second. The paper discusses the results of research on the basic transport system: the phenomenon of progression at the capstan-tape interface, the mechanism of tape flow to and from the reel and around the capstan. The behavior of capstan tires at high speed and the dynamic response of tapes are discussed. The paper is based on considerable experimental data. Several models of high speed machines are shown.
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Filtering Effects in a Spread-Spectrum Telemetry SystemBinary antipodal direct-sequence biphase modulation is employed (for the purpose of interference reduction) over a channel disturbed by white noise and an "external" coherent sinusoidal interference. Before these are added, the signal suffers distortion in the form of linear filtering whose effects are to be determined. The receiver is a coherent "rematched filter" (matched to the distorted signal). The mean and variance of the detection variable are expressed as an output SNR (signal to noise ratio). The variance is the sum of three components: due to noise, external interference, and self interference. Concise formulas for the first two contributions are developed. The third is approximated and found to be quite small in many cases of interest. Results are applied in the case in which the filter has a bandpass characteristic and external interference is dominant. With fixed signal power entering the filter, there is an optimal chip rate above which filter distortion effects increase faster than process gain; the optimal chip rate is approximately equal to the filter noise bandwidth B (Hertz). For an ideal bandpass filter and a single pole bandpass filter, the optimal chip rates are 1.0B and 0.95B, respectively.
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Apollo ExtraVehicular Communication Telemetry SubsystemThe original Apollo Space Suit Communications System (SCC) was designed to accommodate one Extravehicular Astronaut. Early in 1967, NAS.N established a requirement for an extravehicular Communications System (EVCS) which would enable two astronauts to simultaneously explore the lunar surface. Included in this requirement was a telemetry subsystem to monitor the performance of the portable life support system (PLSS), space suit performance and body functions of each astronaut while on the lunar surface. This paper reviews the EVCS telemetry subsystem design including electrical and functional capability, packaging techniques, reliability and configuration control programs utilized in meeting the stringent requirements of a miniature, high reliability, man-rated electronic system for space applications.
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Low Cost Water Quality Monitoring by Radio TelemetryA radio telemetry water quality monitoring system has been designed and constructed at the Utah Water Research Laboratory (UWRL). The system consists of a central base station at the laboratory and remote field stations located in the river to be studied. The remote field stations operate in the stand-by mode until interrogated from the central base station. Each station is capable of monitoring dissolved oxygen (D. O.), hydrogen ion concentration (pH), electrical conductivity, and temperature. Other variables could be monitored by using appropriate sensors. The prime features that characterize the UWRL system are low cost and relatively small size. These are both realized through the use of printed circuit boards and integrated circuit amplifiers. The remote station is small enough to be portable and can be installed either permanently or temporarily at almost any river location with a minimum of effort. Such a system, costing about $3,000 per field site, will make feasible the monitoring of water quality at points which previously were uneconomical to investigate.
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Doppler Jitter Versus Digital Error RateIn the design of digital communications systems, the error rate is the criterion which is invariably emphasized. In many digital systems, however, there is relative motion between transmitter and receiver which must be controlled by making use of Doppler frequency information. A coherent digital system is herein modeled, in which the trade-off that exists between Doppler measurement capability and subcarrier demodulation error rate is quantitatively presented. System parameters which effect only one of the two above criteria are initially optimized. The dependence of performance on the remaining system parameters is then analytically and graphically presented.
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Evaluation of Protective Masks by Use of Radio TelemetryA telemetering system developed to enable research and development personnel to evaluate physical performance aspects-of US Army protective masks on a quantitative basis is described. Respiration, acceleration, and temperature data generated by a subject wearing a mask can be monitored simultaneously at a point remote from the mask wearer. The system operates in the 216-235 MHz telemetry band using an FM/FM mode. Data transmission in excess of 1/2 mile (via ground wave) has been obtained without experiencing signal deterioration. Data generated can either be recorded directly on a strip chart recorder, magnetic tape recorder or both simultaneously. Data recorded on magnetic tape can be analyzed by use of an Analog Computer. Measurements obtained using this equipment compare in accuracy with that obtained through use of conventional laboratory instrumentation.
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Biotelemetry of EKG Signals Within a Small, Closed ChamberA requirement arose for reliably telemetering EKG data from personnel within a closed metallic chamber to a receiver also located within the chamber. Although there is much information in the literature on biomedical telemetry, it generally deals with propagation of telemetry signals in the clinical laboratory or the field; little, if any, pertains to the problem at hand. Analysis of the environment showed that mathematical prediction of the propagation characteristics of the chamber would be difficult, if not impossible, due to its odd interior configuration. An empirical approach was taken. Several system approaches were considered; an FM/AM system and an FM/FM system were built and each evaluated in the actual environment. Data are presented on test results. A successful system is discussed, including a description of the receiving antenna network employed to ensure reception of the transmitted signals regardless of the location of personnel within the chamber. Conclusions regarding the chamber characteristics are given.
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Wideband Fiberoptic Analog Information LinkA high frequency data transmission system which is unaffected by high energy electromagnetic fields is described. The system utilizes a gallium arsenide (GaAs) infrared light emitting diode as the transmitting source, a glass fiber optic light guide as the transmitting medium, and a photomultiplier tube (PMT) as the optical receiving sensor. The photomultiplier output is displayed on a real-time wideband oscilloscope where it is permanently recorded on film. The overall system concept was chosen and each major component type was evaluated for optimum performance in this application. It was determined during the feasibility phase of the program that cryogenic cooling of the GaAs diode would be necessary to obtain high frequency response and high signal to noise ratio (SNR). Liquid nitrogen (LN₂) was chosen as the cryogen due to its low temperature, low cost, availability, and relatively long holding time. The described system results in a 40-ft fiber optic, analog data link with a frequency response of 80 MHz and a dynamic range of 32 db. The system is not susceptible to electromagnetic fields.
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Why Data System StandardsThis paper discusses some ideas about data system standards which have been developed at the Goddard Space Flight Center (GSFC) of NASA over a period of about nine years, mainly as the result of experience gained in using the Space Tracking and Data Acquisition Network (STADAN), a collection of tracking, command, and telemetry stations for ground support of scientific satellites. The authors have found that the purposes and uses of data system standards are often misunderstood. To aid in clarifying this situation, they have described the growth and current implementation of the working approach to standards at GSFC. This approach is conditioned by the operating environment and by a number of administrative decisions, which are discussed. The areas included in the existing GSFC standards and some of those planned for future coverage are described, and some considerations bearing on the feasibility of combining GSFC and other data system standards are examined.
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Performance of Partially Coherent Binary ReceptionThis paper considers the performance of a partially coherent detector of phase-shift keyed (PSK) modulated binary data, where the receiver's phase reference is noisy and derived from the carrier component of the received signal by means of a narrow band tracking filter (phase locked loop). The statistics of the detector output are derived and the bit error probability is graphically illustrated as a function of the data channel signal to noise ratio, the signal to noise ratio existing in the phase lock loop bandwidth and the phase lock loop bandwidth to bit rate ratio. The results obtained for the single channel partially coherent detector are used to derive the performance of binary data detection after maximum ratio diversity combination of the two video signals, each of them being demodulated by partially coherent detectors.
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A New Bandlimited M-ARY Non-Coherent Telemetry SystemIn this paper new M-ary non-coherent signal structures that require less transmission bandwidth than conventional FSK are presented. A method of synthesizing these signal sets by the use of frequencies or tones is given. In order to evaluate system performance, an approximation to the error probability for large signal energy-to-noise spectral density ratio is derived. Using this formula certain signal structures are evaluated for M = 8, 16, and 32. It is shown that for error rates of less than 1 x 10⁻³, the signal structures that reduce the transmission bandwidth by 25% are within 1 dB of the corresponding FSK signal set. Thus these signal structures provide an efficient method of communication when the bandwidth is constrained to be less than required for the transmission of FSK.
