RSS 1.0International Telemetering Conference Proceedings, Volume 13 (1977)
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 thirteenth International Telemetering Conference, October 18-20, 1977. The conference, sponsored by the International Foundation for Telemetering, was held at the Hyatt House Hotel in Los Angeles, California.
QUESTIONS?
Contact https://telemetry.org/contact-us/ with your questions about the International Telemetering Conference Proceedings.
Recent Submissions
-
International Telemetering Conference Proceedings, Volume 13 (1977)International Foundation for Telemetering, 1977-10
-
Results of a Q-M/PSK Data Modem Performing in a Hybrid, Voice and Data Mode, Through the ATS-6 SatelliteThe Transportation Systems Center (TSC), under the sponsorship of the FAA, has been involved in the development of advanced voice/data multiplexed modems applicable to ground-aircraft communications via satellite in support of the AEROSAT program. TSC was assisted by the Canadian Ministry of Transport (MOT), Communications Research Center (CRC), in the planning and conducting of recent flight test experiments using the NASA ATS-6 satellite.
-
Sideband Lock SCPDM Modem for Simultaneous Voice and Data CommunicationsA modem technique for simultaneous transmission of voice and digital data is presented. The salient feature of this technique is the use of quadrature carrier multiplexing of a suppressed clock pulse duration modulation (SCPDM) signal with a biphase NRZ data stream. A novel method for separating the voice and data components at the receiver is described. Data bit error rate and voice intelligibility test results are presented and discussed.
-
The Development of a Satellite On-Board MicrocomputerThe paper describes a miniaturized computer for space use that is being developed under a contract from Intelsat. An all CMOS design is used with the corresponding low power and high speed associated with CMOS. Extensive use is made of LSI and the computer is based on the Intersil or Harris 6100 microprocessor. This has the same architecture as the PDP8-E and the extensive range of DEC PDP8-E software can be used. Provision has been made for both serial and parallel input/output ports. A development prototype is described that has serial and parallel ports. The associated memory is expansible up to 32K words in 2K blocks. RAM or PROM can be used or interchanged in blocks of 256 words. A programmable timer is included for real time applications. A bench model of the computer is also described which is made for program development. It is not to the same environmental standards as the development prototype but has the same facilities together with a control panel and provision for a teletype. The use of the Bench Model for software development is described.
-
Processing Radiation Data on Board TIROS-N SatelliteThe function of the data processing unit (DPU) as part of a space environment monitor subsystem is described, with emphasis on special features in the data handling process. Important design goals for achieving DPU performance are outlined. Design implementation to achieve these goals is discussed. Some of the more complex circuits are described in detail as examples of onboard data processing. The packaging approach for effecting savings in weight and power is also presented.
-
An Integrated Error Correcting/Pseudo Random Communication SystemThis paper describes a pseudo random (PN) communication system with an integral error correcting code. The error codes are again based on maximal length sequences and simultaneously provide coding gain with bandwidth expansion. A basic modem starting at 2400 bps data rate and expanded to a 5 Mbps chip rate is described. Theoretical and hardware test results are presented to verify the concepts. Finally, synchronization of this system is discussed. A PN range extension concept is developed which improves the acquisition time with only a trivial increase in system complexity.
-
Double Quadriphase Modulation/Demodulation Technique for Three-Channel Communication LinkA modulation technique for a three-channel communication link is introduced. The structure of the modulator is such as to form an unbalanced quadriphase signal wherein the high rate data stream is bi-phase modulated on the in-phase carrier component, while the sum of the two lower rate signals is bi-phase modulated on the quadrature component of the same carrier. The sum of the two lower signals is, in turn, formed by modulating with the respective data streams the in-phase and the quadrature components of a square wave subcarrier. At the demodulator, the tracking of the carrier and the subcarrier is performed by two independent Costas loops. The demodulation of the high data rate signal is carried out after establishing the carrier reference signal, while the lower rate signals are demodulated after the subcarrier loop recovers the subcarrier. In this paper, the performance of the two loops is analyzed and the expressions for the tracking errors are derived. Finally, a numerical example pertaining to the Space Shuttle-to-TDRS Ku-band link is presented for illustration.
-
Quadrature Modulation Hybrid Voice and Data ModemThe Quadrature Modulation Hybrid Modem is a new system designed to provide voice only, data only, or combined voice and data communication. It provides good voice intelligibility at low values of C/N0 by making use of a quadrature modulation technique which permits essentially nonthresholding demodulation of the voice signal. Power sharing between voice and data signals can be easily changed to accommodate different requirements. Intelligibility tests have been performed and indicate an intelligibility of 90% in the voice-only modem at a value of C/N₀ of 43 dB-Hz, and an intelligibility of 80% in the combined voice and data mode at a value of C/N₀ of 43 dB-Hz with an error rate for data of 10⁻⁵.
-
The Apollo VHF Ranging SystemRedundancy of functions on manned space flights has been an important concept for crew safety. However, a redundant system generally implies doubled weight - a luxury that can not easily be afforded on a spacecraft. The Apollo Command Module- Lunar Module rendezvous mission was performed with the rendezvous radar system. RCA developed a VHF Ranging System, which permitted the voice/telemetry radios to be adapted as a backup for the radar's ranging function at relatively low additional weight. The proven accuracy and reliability of the VHF Ranging System resulted in its selection as the sole rendezvous sensor for subsequent earth orbital manned missions. The constraints imposed by existing radios are discussed, the ranging options and selected implementation are described, and the system accuracy is reviewed.
-
A Satellite Automatic Control SystemThe primary task of existing satellite control centers is to automatically monitor the operational performance of existing satellites and to manually generate control commands so that these satellites remain within specified operational limits. This paper describes some basic characteristics of an existing satellite control center and identifies a method that may be employed to gradually introduce automatic commanding to the facility. Candidate methods of automatic commanding are described.
-
Design Concepts for a Highly Reliable Multimicroprocessor System for Communication SatellitesOver past years, the microprocessors have been used widely and efficiently for many applications. Some of them have become industrial standards, and the question arised how to use them most efficiently for space applications. The paper describes the design concepts which have directed the study and the breadboarding of a trimicroprocessor system and its monitoring software. These concepts have been traded off for reaching a high system overall availability and flexibility. The multiprocessor is organized around C-MOS microprocessors and a time shared/common bus, designed for reliable operations. The monitoring software is especially developed to yield a triple redundancy for critical (i.e. mission success dependent) software functions and to assure the mutual failure independency of the application programs. On board telecommunication satellites, the multiprocessor structure have been found better suited for reliability, probability of mission interruptions and its capability of degraded operation when it was compared to a classical stand by redundant monoprocessor array. At the end of the year, the triprocessor system will be integrated into a satellite attitude control simulator for a system closed-loop test with an air bearing table and actual satellite equipments.
-
Some Operational Considerations in Deploying Anti-Jam CommunicationsOperational and deployment considerations are described to enhance the performance of jam resistant communications. The potential different ground propagation characteristics of spread spectrum and CW type waveforms are used to the advantage of the communication system. Emphasis is placed on the use of tactical relay to continuously optimize against the jammer. Tactics such as spoofing are described as a technique in confusing the intelligent jammer. The objective of this paper is to illustrate how anti-jam communications with nominal AJ performance improvement can effectively be employed in a ground environment. These include the brute force and the so-called intelligent or sophisticated jammer. For many years the utilization of anti-jam communications has been stifled in anticipation or the optimum solution against the optimum jammer. When evaluating a "one on one" scenario where the jammer is dedicated to jamming a specific link there is an unending subset of tradeoffs of optimum techniques to consider. However, when the jammer is trying to disrupt communications along a broad geographical axes. the techniques of jamming and communicating should be based on more general operating conditions. The ground communications environment in the presence of ground-based jamming presents the greatest opportunity for improving performance as a function of propagation anomalies and the use of relay. Airborne terminals within line of sight of the jammer have the most severe jamming environment. Ground based terminals generally will have an advantage of terrain against the ground based jammer. Those links that exhibit poor communications margin should always have the option of an alternate route in a jamming environment. The alternative to an alternate route is to provide excessive performance margins for worst case analysis. Unfortunately there is a significant cost factor associated with this latter approach. An important element of the scenario is the concept of position location. The use of position location and reporting equipment enables the apriori determination of appropriate links by different classes of users. As an example an aircraft can maneuver close to a ground terminal for communications to utilize the advantage of range ratio. This can be done in the worst case of a close Air Support Mission where the FO must provide voice or digital data to direct a strike at several mobile targets. At high altitudes the AC may be jammed but at low altitude the link may be viable. At low altitudes the aircraft A-G link will be constrained to a small geographic area and must therefore know which area to cover. The use of GPS can also be enhanced at low altitudes against the ground based jammer if acquisition of the GPS signal can be speeded up. The use of a digital matched filter (DMF) for CA code acquisition can provide this capability.
-
ECM/ECCM Effects on Voice TransmissionsAn evaluation methodology for conventional and ECCM voice communications is presented, wherein intelligibility of the received message rather than error rate or signal-to-noise ratio is the quantity measured. This allows the engineer to include the psychoacoustic phenomena of a human listener in his system design considerations. Analyses have been performed which allow transformation of speech articulation test results into data more meaningful to the communications engineer. Since message intelligibility is established after baseband reconstruction of the voice signal, this method is universally applicable to most voice transmissions. It is insensitive to the nature of the medium, modulation, and interference sources. Examples are presented showing applications of these guidelines to the design of frequency hopping radios. Tests run on a simulator confirm the analyses. A sample tape is available to demonstrate some of the effects.
-
Pseudo-Random Code Sidelobe CancellerDuring acquisition of direct sequence pseudo-noise signals, time sidelobes are produced at the correlator output which will degrade detection performance. These sidelobes may be the result of additive noise, channel distortions, deliberate jamming or the non-ideal correlation function of truncated code sequences. In order to minimize these sidelobes, special codes can be selected based on their low sidelobe levels, or some special sidelobe reduction or cancellation algorithm may be devised. A sidelobe cancellation algorithm for use with LSI correlators has been simulated. Segments of a maximum length code word as well as a totally random bit stream were tested. The simulation results show that the largest sidelobes are reduced by a small amount; however, the majority of the sidelobes are reduced by as much as 6 dB. Consequently the false alarm rate for a particular threshold setting may be reduced. A compatible technique for the derivation of a CFAR reference from the same correlator was also successfully simulated.
-
JTIDS Modular Design to Use SAW DevicesThe Joint Tactical Information Distribution System (JTIDS) concept is designed to integrate the military's needs for communication, navigation and identification equipments into a cost-effective avionic suite. A key element to be used in achieving these goals is the surface acoustic wave (SAW) bandpass filter...in the form of a bandwidth selectable module. In order to satisfy the JTIDS requirements of today, as well as the Tactical Information Exchange Systems (TIES) of the future, it is necessary to utilize state-of-the-art SAW resonator/filter designs ... in conjunction with more conventional SAW bandpass filter technology. It is this approach that will make possible the quality performance required in a small, low cost module.
-
Multiple Access Methods in Commercial Communications SystemsTime division and/or code division multiple access techniques based on spread spectrum modulation and demodulation technology have found wide application in military systems. These techniques also offer advantages for use in systems that allow for large numbers of users in civil communications systems. This paper considers spread spectrum multiplexing as a technique that allows time division multiplexing multiple access to communications networks. It also provides for multiple networks to operate in the same band through code division multiplexing.
-
Experimental Comparison of Pulse Code Modulation Codes for Magnetic RecordingThe bit error probability (BEP) versus signal-to-noise ratio (SNR) was experimentally determined for Non-Return-to-Zero-Level (NRZ-L), Bi-Phase-Level (BIΦ/-L), Delay Modulation (DM) and Miller Squared (M²) codes for a bandpass channel. This was done by passing the data through a 400 Hz to 500 kHz Bessel bandpass filter and linearly adding noise. The power spectral density of the noise was shaped to match the noise out of an analog magnetic tape recorder running at 30 inches per second (in./s). This provided a simulation of an optimum wideband 2.0 MHz tape recorder running at 30 in./s (no flutter, tape dropouts, etc.). The bit rate, pattern, and code to be tested were then selected. The SNR was varied until the bit error probability was approximately 10⁻⁶ With a commercial Pulse Code Modulation (PCM) bit synchronizer with a "good" dc restorer and a pseudo-random pattern at 1.0 megabits per second (Mb/s) (33.3 kilobits per inch (kb/in.) equivalent packing density), NRZ-L had a 4 dB SNR advantage over DM and a 14 dB advantage over BIΦ/-L for a BEP of 10⁻⁶ through the bandpass channel. At 1.5 Mb/s, NRZL had a 6 dB advantage over DM and a 10⁻⁶ BEP was not achievable with BIΦ/-L coding. For a synchronizer with no dc restoration NRZ-L had only a 1 dB advantage over DM at 1.0 Mb/s and also only a 1 dB advantage at 1.5 Mb/s. M² gave the same results as DM for pseudo-random data. However, M² was relatively insensitive to patterns while DM and NRZ-L required a higher SNR with a "good" dc restorer and lost synchronization completely with no dc restorer for worst case 16-bit repeating patterns.
-
A-M/AGC Weighted Pre-Detection Diversity CombiningA method has been proposed for improving the performance of automatic gain control (agc) weighted diversity combiners in the presence of fast fading radiofrequency (rf) signals by use of the amplitude modulation (a-m)(detected linear intermediate-frequency (i-f) envelope) in addition to the agc voltage to weight the combiner. Also suggested was a method for selecting the channel with the best signal-tonoise ratio (SNR) by use of the a-m and agc voltages. Experimental hardware has been constructed for evaluation of three configurations: an a-m/agc weighted combiner; an a-m/agc based selector; and an a-m/agc combiner/selector where the criterion for combine or select is determined by the phase error between the two channels. An experimental study was also conducted of the phase-locked loop (PLL) to determine the best configuration and parameter values for the combiner application (where relatively large phase errors are permissible). Data were taken under laboratory and operational (Vandenberg Air Force Base) conditions and are compared with data taken with a commercial agc weighted combiner.
-
Review of Microstrip Antenna Development at the Pacific Missile Test CenterPacific Missile Test Center personnel have been conducting theoretical and experimental studies on microstrip antennas since 1965. A number of operational microstrip antenna systems have been developed. This report reviews development efforts at Pacific Missile Test Center on types of microstrip antenna elements used in these operational systems. Results of near field probing of different microstrip antenna elements are presented. These results are used as a basis to discuss microstrip antenna electrical characteristics such as orthogonal current oscillation, orthogonal charge oscillation, dipole moment of charge distribution oscillation, dipole moment of charge distribution rotation, far field radiation patterns, polarization, etc. Application of microstrip arraying techniques on thin flexible substrates that can be readily mounted conformally to the exterior surface of a missile without missile disassembly is discussed.
-
Telecommunication Applications for CTD DevicesA relatively new type of component, the CTD (Charge Transfer Device) is now available to the commercial market. After five years in the development lab, these parts are finding their way into many applications including telecommunications. This paper will give a brief overview of the device theory and discuss three particular devices: 1) a transversal filter, 2) a Binary Analog Correlator, and 3) chirped transversal filter used to implement a Discrete Fourier Transform.
