• IF DBPSK Modems Design for Command Link and Telemetry Systems

      Hsu, Cherng-Shung; Liang, Junn-Kuen; Lu, Fu-Chao; Chung Shan Institute of Science and Technology (International Foundation for Telemetering, 1986-10)
      In this paper, the 70 MHz IF differential binary phase shift keying (DBPSK) modem is designed and implemented. At the transmitter, the data are first differentially encoded, and then sent to the binary phase modulator, which is followed by a delicatedly designed band pass filter to suppress the undesired sideband spectrum. At the receiver, the DBPSK signal is coherently demodulated by a Costas loop which is carefully analyzed and designed in this paper. In order to maintain the overall loop gain within a desired range for keeping a better loop performance, an IF preconditioning AGC (Automatic Gain Control) circuit is added in the demodulator to keep the IF amplifier output level almost constant even at low signal to noise ratio. In order to improve the false lock due to the data sideband, especially for low rate modems, and to enhance acquisition, a modified Costas loop and an automatic sweep search acquisition circuit are included in the demodulator. Besides the carrier recovery, the bit rate clock must be recovered from the received DBPSK signal. Instead of serial processing, i.e., clock recovery comes after carrier recovery, a parallel processing of the received DBPSK signal is employed, i.e., clock recovery is parallel to carrier recovery. In other words, the carrier and clock recovery circuits independently process the same received DBPSK signal at the same time. The advantages obtained from the parallel processing are faster overall system acquisition and reduction of information loss. The recovered clock is derived from a bandlimited DBPSK signal by an envelope detector followed by a phase-locked loop (PLL). The key features of this suboptimum clock recovery circuits are simplicity and low cost for practical hardware implementation. An example for modem design will be given and the modem will be implemented and then tested. Parameters selection and hardware implementation of important building blocks in the modem circuit are all given careful consideration. Furthermore, the block of the IF AGC, modified Costas loop scheme and sweep search circuits will also be described with emphasis on their key functions. Finally, the bit error rate performance of the experimently implemented modem will be tested and presented.

      Eccles, Lee H.; Muckerheide, John J.; Boeing Commercial Airplane Company (International Foundation for Telemetering, 1986-10)
      The Experimental Flight Test organization of the Boeing Commercial Airplane Company has an onboard data reduction system known as the Airborne Data Analysis/Monitor System or ADAMS. ADAMS has evolved over the last 11 years from a system built around a single minicomputer to a system using two minicomputers to a distributed processing system based on microprocessors. The system is built around two buses. One bus is used for passing setup and control information between elements of the system. This is burst type data. The second bus is used for passing periodic data between the units. This data originates in the sensors installed by Flight Test or in the Black Boxes on the airplane. These buses interconnect a number of different processors. The Application Processor is the primary data analysis processor in the system. It runs the application programs and drives the display devices. A number of Application Processors may be installed. The File Processor handles the mass storage devices and such common peripheral devices as the printer. The Acquisition Interface Assembly is the entry point for data into ADAMS. It accepts serial PCM data from either the data acquisition system or the tape recorder. This data is then concatenated, converted to engineering units, and passed to the rest of the system for further processing and display. Over 70 programs have been written to support activities on the airplane. Programs exist to aid the instrumentation engineer in preparing the system for flight and to minimize the amount of paper which must be dealt with. Additional programs are used by the analysis engineer to evaluate the aircraft performance in real time. These programs cover the tests from takeoff through cruise testing and aircraft maneuvers to landing. They are used to analyze everything from brake performance to fuel consumption. Using these programs has reduced the amount of data reduction done on the ground and in many cases eliminated it completely.

      McConnell, John B.; Baker, Robert L.; Flowers, Harold; Western Space and Missile Center; ITT-Federal Electric Corporation (International Foundation for Telemetering, 1986-10)
      The Western Space and Missile Center (WSMC) plans to precisely synchronize remote instrumentation site timing on the Western Test Range (WTR) using Global Positioning System (GPS) equipment being developed for Tri-Service range applications. This paper describes background information, current WTR timing capability, remote site synchronization requirements, a proposed GPS timing system configuration, and testing approach.

      Cox, Timothy F.; Stanford University (International Foundation for Telemetering, 1986-10)
      Power spectra of M-ary, or multi-level, PCM/FM are calculated for a limited selection of baseband pulse shapes and deviation ratios. Parameter values, such as number levels, symbol rates, and deviation ratios, are determined for those cases in which the corresponding spectra fit into 1, 3, and 10 MHz bandwidth channels. The IRIG specifications are used to produce the spectrum occupancy values from the normailized power spectra densities.

      Skinner, Patrick J.; Ford Aerospace & Communications Corporation (International Foundation for Telemetering, 1986-10)
      Modernizing labor intensive Remote Tracking Stations (RTS), increasing individual station capacity, and providing interoperable links between three separate Air Force satellite networks are the objectives of the Automated RTS (ARTS) program now half way to completion.

      Kurisu, Kurtis Lee; Aerospace Corporation (International Foundation for Telemetering, 1986-10)
      The Space-Ground-Link-Subsystem (SGLS) has been providing Telemetry, Tracking, and Commanding (TT&C) services to the Air Force Satellite Control Facility (SCF) since the late 1960’s. The current transmitter system is comprised of a 10 kW travelling wave tube (TWT) and associated equipment. As solid state technology matures, it is now appropriate to consider alternative approaches. Solid state offers the potential advantages of improved reliability, graceful degradation, high efficiency, and lower life cycle costs. This paper addresses the current status of solid state multi-kilowatt systems development. The present state of solid state power transistors and low loss power combiners are at a stage where high power S-band CW transmitters are possible. The advantages and disadvantages of the state of the technology are discussed as are the practical considerations for integration into SGLS systems applications.

      Wait, D. F.; Baird, R. C.; Daywitt, W. C.; Newell, A. C.; Perera, S.; Repjar, A. G.; CyberLink Corporation (International Foundation for Telemetering, 1986-10)
      The National Bureau of Standards (NBS) has investigated the calibration and measurement support requirements of millimeter wave satellite systems such as MILSTAR. Essentially three new measurement problems arise because of operating in the upper SHF and EHF frequency ranges. First, without adequate methods to measure the atmospheric loss, the accuracy of EIRP measurements in the 20 GHz to 45 GHz range can be no better than 0.5 dB to 3 dB (depending on frequency and antenna elevation angle). The atmosphere absorbs and scatters radiation traveling through it, both reducing the magnitude of and depolarizing a received signal. Second, standards, measurement support services, and some measurement techniques are not presently available from NBS and they are needed to support millimeter wave antenna gain and thermal noise measurements. Of special concern are the effects of connectors and adapters, since they can introduce significant errors into mm-wave measurements. Theird, if the sun and/or moon are to be used for measuring earth terminal G/T, earth terminal antenna gain, or satellite effective isotropic radiated power in the millimeter region, they need to be appropriately characterized at those frequencies. The sun and moon are only useful as measurement sources for antenna systems with gains less than about 50 dB, but most MILSTAR systems are expected to fall in this category.

      Munson, Robert E.; Ball Aerospace Systems Division (International Foundation for Telemetering, 1986-10)
      Microstrip antennas are ideal for telemetry applications, especially when a low profile thin conformal antenna is desirable. This paper discusses omni wraparound, directional fixed beam, and conformal electrically scanned microstrip antennas.

      Calvez, Cliff A.; Deputy Commander for Network Development and Integration (International Foundation for Telemetering, 1986-10)
      This paper presents an architectural overview of the Air Force Satellite Control Facility (AFSCF) with emphasis on the on-going development effort of the AF Satellite Control Network (AFSCN). The AFSCF originated twenty-seven years ago, and has evolved into a global satellite service network. This worldwide network is composed of twelve RTSs, located at seven geographically dispersed locations, and a Satellite Test Center (STC) at Sunnyvale, California. The AFSCF provides real-time telemetry, tracking, and commanding (TT&C) service to Department of Defense (DoD) spacecraft and launch vehicles. To cope with the projected operational workload and to reduce life cycle costs, the AFSCF began a major effort several years ago to modernize the Network. The two programs, (Data Systems Modernization and Automated Remote Tracking Station) in this effort will bring about major changes in the Network’s current configuration and operations concept. Another program, the development of the Consolidated Space Operations Center (CSOC), also introduces major changes to the network architecture. Additionally the formation of the USAF Space Command has profound impacts on the AFSCN and its development effort. With these changes, brought about in response to changing DoD space support requirements, the AFSCF network has grown through expansion and modernization of its tracking, data processing, and communication capabilities. This paper discusses the past, the present, and the impending changes to the AFSCN as it continues to evolve in support of the DoD space programs.

      Hoefener, Carl E.; Wells, Lawrence; Interstate Electronics Corporation (International Foundation for Telemetering, 1986-10)
      GPS will provide a very attractive means to track kinetic energy weapons in space for the Strategic Defense Initiative programs for system test and evaluation. However, the small size and very high dynamics of these vehicles complicate the use of GPS. This paper considers these issues and suggests a solution.

      Ricci, Fred J.; RAMCOR, Inc. (International Foundation for Telemetering, 1986-10)
      With the advent of higher and higher data rates and signal processing requirements for onboard satellite processing, the need for a faster computational capability has grown well beyond the capabilities of existing space-qualified computers. This has become a major technical issue in the design of next-generation satellite systems for commercial and military use. As a matter of fact, it is becoming a major issue in the Strategic Defense Initiative (SDI), the development of the MILSTAR Satellite System, and in future infrared (IR) and radar satellites/platforms. Future platforms will require larger onboard processing systems than are currently in use in order to satisfy their data processing and commandand-control communications requirements. The platforms of tomorrow will be very sophisticated and therefore expensive. For such systems to have acceptable life-cycle costs, they must be produced from highly reliable hardware that will operate in space for system design lifetimes of up to 10 years. This paper will summarize the processing needs of onboard systems and present a specific example of the design of a VLSI/VHSIC processor for an onboard satellite controller in an airborne platform.

      Kumar, Rajendra; California State University (International Foundation for Telemetering, 1986-10)
      A new least squares algorithm is proposed and investigated for fast frequency and phase acquisition of sinusoids in the presence of noise. This algorithm is a special case of more general adaptive parameter estimation techniques. The advantages of the algorithms are their conceptual simplicity, flexibility and applicability to general situations. For example, the frequency to be acquired can be time varying, and the noise can be non-gaussian, nonstationary and colored. As the proposed algorithm can be made recursive in the number of observations, it is not necessary to have a-priori knowledge of the received signal-to-noise ratio or to specify the measurement time. This would be required for batch processing techniques, such as the Fast Fourier Transform (FFT). The proposed algorithm improves the frequency estimate on a recursive basis as more and more observations are obtained. When the algorithm is applied in real time, it has the extra advantage that the observations need not be stored. The algorithm also yields a real time confidence measure as to the accuracy of the estimator.

      MILWAY, WILLIAM B.; HQ, USATECOM (International Foundation for Telemetering, 1986-10)
      The use of some type of target as an aiming point has been an essential part of weapon system testing since the beginning of history. Today, with the complex arsenal of high technology weapons used by the Army, the need for targets is critical. There is currently a shortfall in the performance that can be obtained from existing targets. The development of new and improved targets and target control systems will be a high priority task in the next decade.

      Cumming, Colin J.; Hoy, Leslie D.; Frontier Engineering, Inc. (International Foundation for Telemetering, 1986-10)
      This paper describes a microprocessor based multi-channel signal analyzer system for use with telemetry system pre- and post detected video signals. In the application described here, the system software is configured to simultaneously analyze up to 16 telemetry signals, compute an estimate of the SNR for each, and then select the best for output to real time recording equipment. The SNR is estimated by comparing the total signal energy with the signal power observed in an unused portion of the signal spectrum. The signal analysis filters are fully programmable over a range of 10 KHz to 2 MHz and may be set up to analyze a wide variety of telemetry formats. The microprocessor system also supports printed output of signal status and remote programming.

      Mohanty, Nirode; The Aerospace Corporation (International Foundation for Telemetering, 1986-10)
      The performance is presented of a spread spectrum communication system utilizing binary phase shift keying (BPSK), differential binary phase shift keying (DBPSK), and 8-ary frequency shift keying (FSK) signals in the presence of partial band jamming noise and tone noise. A combination of coding, interleaving, and diversity techniques provides the best antijamming capability.

      Bokulic, Robert S.; The Johns Hopkins University (International Foundation for Telemetering, 1986-10)
      The noise performance of the sawtooth phase detector when demodulating a sinusoidal subcarrier plus direct data modulation is studied. At predetection signal-to-noise ratio (SNR) levels of about 10 dB or more, significant improvements in the postdetection SNR of the subcarrier can be obtained using the sawtooth detector rather than a linear multiplier. Below predetection SNR levels of about 10 dB, significant improvements can still be obtained; however, a threshold occurs and the performance degrades until leveling off at 3.2 dB worse than that of a linear multiplier. The predetection SNR level where the sawtooth detector performance becomes worse than that of a linear multiplier depends upon the subcarrier and direct data modulation indices. Performance curves are given between predetection SNR levels of -20 dB and +20 dB for various values of subcarrier modulation index and direct data modulation index.

      Lee, Lester H.; Recortec, Inc. (International Foundation for Telemetering, 1986-10)
      Description of various off-line magnetic tape cleaning techniques and testing process to measure defects of tape before using it for tape recording applications. Discussions are made on the type of cleaning methods and also the ways and means to achieve better evaluation results.
    • Review of Spectrum Support Information for U.S. Air Force Telemetry Equipment Development and Procurement

      BARNES, LARRY; U. S. Air Force Frequency Management Center (International Foundation for Telemetering, 1986-10)
      This paper presents a review of spectrum support information as it pertains to the development and procurement of U. S. Air Force Telemetry Equipment. Highlights of this review include: Definitions of terms used in this paper that are peculiar to spectrum management; frequency bands encouraged by the U. S. Air Force for Telemetry Equipment Development and Procurement for use in the United States including station, channeling, and bandwidth information; frequency bands discouraged by the U. S. Air Force for Telemetry Equipment Development and Procurement for use in the United States; summary of Telemetry Equipment Electromagnetic Compatibility (EMC) Parameters required when requesting certification of spectrum support in the United States; and finally a summary of telemetry equipment EMC standards associated with the certification of spectrum support in the United States.

      McConnell, John B.; Hoefener, Carl E.; Western Space and Missile Center; Interstate Electronics Corporation (International Foundation for Telemetering, 1986-10)
      The NAVSTAR Global Positioning System (GPS) allows extremely accurate global determination of time as well as position and velocity. Currently, the DoD test and training ranges of the United States are working towards using GPS to obtain position and velocity information and recently attention has been given to using GPS for precise range timing. This paper provides background information, discusses the advantages of using GPS for range timing, and describes two timing system configurations using Tri-Service GPS range equipment.

      Krishen, Kumar; Erwin, Harry O.; Johnson Space Center (International Foundation for Telemetering, 1986-10)
      This paper presents a review of the ranging and tracking systems/techniques used in the past NASA programs. A review of the anticipated requirements for future rendezvous and docking operations is also presented as rationale for further development of the technology in this area. The first American rendezvous in space was between Gemini VI-A and Gemini VII and took place on December 15, 1965. The Gemini vehicles were equipped with a noncoherent pulse radar. The target vehicle carried a transponder to assist the radar in target acquisition. Angle tracking was accomplished by the phase-comparison monopulse technique. In the Gemini, Apollo, and Skylab programs, the rendezvous and/or docking were manual operations supported by radar measurements and visual observations. The Shuttle rendezvous radar is a Ku-band, pulse-Doppler radar which doubles as a communications transceiver. This radar is not accurate enough to support close-in stationkeeping or docking. An automatic soft-docking capability has been established as a requirement for future space operations. Millimeter wave and laser radar systems have shown promise in satisfying the needed accuracy requirements and size constraints (for space applications) compared to the microwave systems for proximity attitude, position and velocity measurements. A review of these systems and their capabilities is presented in this paper. Rather than developing a separate sensor to satisfy the requirements of each new spacecraft, a hybrid design is proposed for a versatile system which can satisfy the needs for different spacecrafts and missions.