Now showing items 50-69 of 97

• #### A NEW ORTHOGONAL MULTIPLEX SYSTEM

The basis of mathematics which can form a telemetering system is orthogonal functions. Three kinds of orthogonal functions are used up to now. First of them is sine and cosine functions. Second one is block pulse functions. The third one is walsh functions. Their corresponding systems are FDM, TDM and SDM. There are also other orthogonal sets which can form telemetering system, such as Legendre polynomials and Hermite polynomials. Hewever. They are too complex for engineering practice. Except these functions mentioned above, is there any other orthogonal functions which is suitable for engineering practice? In this paper we presented a new type of orthogonal functions. Its construction is similar to Walsh functions. The amplitudes of the functions are +1, -1 and 0. In the sence that they close the gap between walsh functions and block functions, it is called Bride functions. The definition and properties are discussed in more detail here. The construction of system is also similar to that of SDM.
• #### A NONMYSTICAL TREATMENT OF TAPE SPEED COMPENSATION FOR FREQUENCY MODULATED SIGNALS

In this paper, the problem of non-constant tape speed is examined for frequency modulated signals. Frequency modulation and demodulation are briefly reviewed. Tape speed variation is modeled as a distortion of the independent variable of a frequency modulated signal. This distortion produces an additive amplitude error in the demodulated message which is comprised of two terms. Both depend on the derivative of time base error, which is the flutter of the analog tape machine. The first term depends on the channel’s center frequency and frequency deviation constant as well as flutter, while the second depends solely on the message and flutter. The relationship between the additive amplitude error and manufacturer’s flutter specification is described. Relative errors and signal-to-noise ratios are discussed for the case of a constant message to gain insight as to when tape speed variation will cause significant errors. An algorithm which theoretically achieves full compensation of tape speed variation is developed. The algorithm is confirmed via spectral computations on laboratory data. Finally, the algorithm is applied to field data. The reference is a temperature signal which is a non-zero constant, and the message is a pressure signal. The spectrum of the uncompensated message is clearly contaminated by the additive amplitude error, whereas the spectrum of the compensated message is not. Incorporation of this algorithm into the data-playback/data-reduction procedures is shown to greatly improve the measurement signal accuracy and quality. The treatment is nonmystical in that all derivations are directly tied to the fundamental equations describing frequency modulation and demodulation.
• #### AN OVERVIEW OF CONFORMAL ANTENNA DESIGN TECHNIQUES USEFUL FOR TELEMETRY APPLICATIONS

Several conformal antennas useful for telemetry applications are described. These antennas make use of dielectric-loaded cavity, edge-slot, microstrip, and dielectric rod radiator design techniques. Critical design parameters, modes of radiation, and theoretical considerations are discussed, as well as intrinsic properties and characteristics of the dielectric materials used. Experimental data relating to impedance, gain, polarization, and bandwidth are given. Also presented are prototype telemetry antennas and performance characteristics. The conformal antennas are flushmounted and designed as an integral part of the body structure. These antennas are electrically small and compact, occupying minimial space. They can be designed efficiently for operation in the telemetry frequency band to produce the desired radiation pattern coverage. Simplified construction and low cost are among the other advantages realized.
• #### PERFORMANCE OPTIMIZATION OF PCM/SCO TELEMETRY SYSTEMS

These hybrid TM system design procedures indicate how PCM channel performance comparable with that obtainable from an optimally designed PCM/FM transmission system may be obtained even though numerous subcarrier channels are included in the system. Optimal design goals are those that permit satisfactory telemetry system operation with a minimum of transmitted power. By careful control of the transmitter modulation levels and the use of predetection filtering during playback, a lowering of the PCM channel’s threshold, equivalent to at least quadrupling the transmitter power over conventional practices, is obtained. This report briefly discusses the design objectives of FM/FM and PCM/FM systems followed by a more detailed discussion of hybrid systems using FM subcarriers above the PCM signal on the baseband. A simplified, but comprehensive, discussion of FM sidebands is presented in the appendices to aid in understanding the limits and restrictions in this hybrid TM system design procedure.
• #### PHASE AND FREQUENCY TRACKING CONSIDERATIONS FOR HETERODYNE OPTICAL COMMUNICATIONS

In heterodyne optical communications, phase or frequency tracking is generally needed to avoid performance degradation when signaling in the presence of laser frequency jitter and Doppler shifts. This paper examines a phase-lock loop approach for BPSK and two forms of frequency tracking for MFSK. Using a statistical model for laser frequency instability, the performance of these schemes is calculated by a linear analysis of the tracking loop in the small-error regime.
• #### PLANETARY SOIL WATER ANALYZER (PSWA) PROTOTYPE

A microprocessor-based differential scanning calorimeter is being designed for eventual use in planetary soil water analysis. The uniqueness of this effort is in the use of the microprocessor as an integral section of the system control loops, instead of as merely an auxilary processor of output data. The use of differential scanning calorimetry is advantageous in determining water content of soil samples. The basic idea is to use two matched ovens, one with a soil sample included. The average temperature of the ovens is forced to track a desired programmed temperature (normally a slow ramp) with one control loop, while a second control loop forces the oven temperatures to be equal, even during a transition. The power necessary to keep the temperatures equal is monitored, containing information as to the transition energy, and thus the water content at programmed water transition temperatures. This approach uses the microprocessor to close both of the loops, taking oven sensor temperatures as an input, and providing power duty cycles as outputs. In actuality, two microprocessors are used - a slave to accumulate and process sensor information, and a master to generate the loop control, output data control, and temperature program control. The PSWA performance is compared to a state-of-the-art commercial instrument using analog loop control. The major advantage of the microprocessor loop control utilized in the PSWA is the capability of remote operation, including remote alignment and adjustment. Further advantages include accommodation of oven changes with software reprogramming, a flexible single oven capability, correction for system nonlinearities using software, and auto gain and auto zero control for the sensor circuitry. The analog loop control approach has somewhat better sensitivity, resolution, and noise performance. The current phase of the development of the PSWA is a feasibility study and circuit design, performed for the Planetary Geology Program Office, NASA Headquarters. The next developmental phases would include breadboarding, software design, testing, and evaluation. In conclusion, this instrument is a significant advance in the state-of-the-art for automatic water measurements, and will be of great value in further planetary exploration.
• #### POLARIZATION DIVERSITY CAPABILITY THROUGH SAMPLING AT THE RF LEVEL

Novel RF circuitry for selecting the stronger of two telemetry signals (RHCP or LHCP) is presented. Polarization diversity capability with uninterrupted data flow can be achieved without using two expensive single channel data receivers and a diversity combiner. In certain dedicated systems only a single AM/FM receiver is required. This paper describes the RF signal processing and logic circuitry of a developed system and describes how it is applied in a lightweight polarization diversity single channel monopulse tracking system.
• #### POWER COMBINING AND SIGNAL ROUTING IN THE GALAXY TT&C EARTH STATION

This paper describes the signal routing and power combining function of the C-band uplink frequency signals in the Galaxy TT&C earth station.
• #### POWER EFFICIENT OPTICAL COMMUNICATIONS FOR SPACE APPLICATIONS

Optical communications technology promises substantial size, weight and power consumption savings for space to space high data rate communications over presently used microwave technology. These benefits are further increased by making the most efficient use of the available optical signal energy. This presentation will describe the progress to date on a project to design, build and demonstrate in the laboratory an optical communication system capable of conveying 2.5 bits of information per effective received photon. Such high power efficiencies will reduce the need for photon collection at the receiver and will greatly reduce the requirements for optical pointing accuracy, both at the transmitter as well as the receiver. A longer range program to demonstrate even higher photon efficiencies will also be described.
• #### PRESAMPLING FILTERING, SAMPLING AND QUANTIZATION EFFECTS ON THE DIGITAL MATCHED FILTER PERFORMANCE

Due to the increased capability and reduced cost of digital devices, there has recently been a growing trend to digitize the matched-filtering data detector in the receiver. Comparing with an idealized integrate-and-dump analog matched filter, the digital matched filter (DMF) requires more Eb /No in order to achieve the same bit error rate performance because of the presampling filtering, sampling, and quantization effects. This paper analyzes the performance degradation resulting, separately and jointly, from these three effects. Quantitative results are provided for commonly chosen sets of design parameters. For a given performance degradation budget and complexity limitation, these results could be applied to choose the optimum DMF design parameters including the presampling filter bandwidth, the sampling rate, the number of quantization bits, and the spacing between adjacent quantization levels.
• #### PROCESSOR TECHNOLOGY OFFERS UNREALIZED FLEXIBILITY IN TOMORROW’S TELEMETRY GROUND STATIONS

Today’s state of the art in semiconductor technology coupled with innovative computer architecture techniques can provide tomorrow’s telemetry industry with advanced ground station capabilities. Computer systems have traditionally been used to process all of the telemetry data. As data transmission speeds increase, the computer system can no longer handle real time processing so preprocessors are being used to handle the additional computational requirements. An alternative approach is to embed special purpose processors into applicable elements of the front-end equipment. These processors can be optimized for the function they are to perform, which prevents under utilization of processing power and enhances the flexibility and performance of the front-end element. These special purpose processors take up little real estate when implemented with todays LSI and VLSI semiconductors. The modules which are ideally suited for this type of technology are serial data correlators, decommutators, real time data correction, engineering units conversion, quick look display, data simulation and many special application modules. These processing elements provide the building blocks for a very powerful, cost effective family of modular telemetry and communications products for the 80’s and beyond.
• #### PROGRAMMABLE TELEMETRY TEST SYSTEM

The U.S. Navy has traditionally operated several missile ranges around the world. However, as the exercises it conducts require greater areas and improved security, it has taken the more ambitious exercises to open ocean, away from ranges. Portable shipboard Telemetry Receiving Systems are designed based on similar methods to those used by range system designers. However, the portable field station must be very small (less then 600 lbs) and system designers are hard pressed to include sophisticated hardware to offset the lower performance of light weight front ends. After the design stage, it is always found that no further weight or volume may be allocated to test equipment. The result has been to practice exercising the live round (missile) for the purpose of testing the ground station. This Test System was designed to meet a need for a portable system to test shipboard telemetry systems used for evaluating performance of missile systems in the surface missile fleet. The technical information presented describes the capabilities of a small test system that is programmable to accurately simulate any missile in the current Navy inventory. It provides test and calibration signals so that telemetry system status may be verified, giving the field operator unprecedented confidence in the station’s condition. The Programmable RT Test System is a product of Navy’s Engineering Initiative Program which supports limited engineering efforts designed to enhance service to the fleet.
• #### PULSE CODE MODULATION TELEMETRY

This paper discusses the performance of pulse code modulation/frequency modulation (PCM/FM), pulse code modulation/phase modulation (PCM/PM) and phase shift keying (PSK) in the “real-world” of range telemetry. The topics addressed include: 1. Radio frequency (RF) spectra 2. Bit error rate (BER) versus pre-detection signal-to-noise ratio (SNR) 3. Peak carrier deviation 4. Premodulation and receiver predetection filtering 5. PCM codes 6. Magnetic recording The purpose of this paper is to provide the reader with information needed to choose the best modulation method, PCM code, premodulation filter bandwidth and type, receiver settings, and recording method for a particular application.
• #### RADSCAN A NOVEL CONICALLY SCANNING TRACKING FEED

This paper presents a description of RADSCAN, a novel conically scanning tracking feed which has only one moving part and utilizes a solid state optical commutator for reference. The feed operates continuously from 1435 to 2400 MHz thereby covering all the existing telemetry bonds in addition to the proposed new bond from 2300 to 2400 MHz. The performance of RADSCAN is compared to that obtainable with the single-channel monopulse technique.
• #### RANGE STANDARDS PANEL DISCUSSION

The Telemetry Group (TG) of the Range Commanders Council is the primary means of exchanging telemetry technical and operational information and coordinating and standardizing systems, techniques, methods, and procedures. The TG is concerned with such telemetry gathering instrumentation as airborne sensing devices and modulation and multiplexing equipment. In addition, the group monitors developments in telemetry processing and storage systems and special display devices. The group is also responsible for writing and updating the Telemetry Standards Document and a series of five volumes on Text Methods for Telemetry Systems and Subsystems.
• #### REAL-TIME DATA DISPLAY FOR AFTI/F-16 FLIGHT TESTING

The overall objective of the advanced fighter technology integration/F-16 (AFTI/F-16) advanced development program is to demonstrate, separately and in combination, advanced fighter technologies to improve air-to-air and air-to-surface weapon delivery and survivability. Real-time monitoring of aircraft operation during flight testing is necessary not only for safety considerations but also for rapid preliminary evaluation of flight test results. The complexity of the AFTI/F-16 aircraft requires an extensive capability to accomplish real-time data goals; this paper describes that capability and the resultant product.
• #### RECOVERY OF PCM TELEMETRY DATA IN THE PRESENCE OF INTERFERENCE SIGNALS

PCM data is recorded on magnetic tape on-board the Space Shuttle during flight. After the vehicle has landed these tapes are played back into a laboratory tape recorder and copies or dubs are made. PCM data from the vehicle is also recorded during manufacture and preflight testing and dubs of these tapes are made. Signals from other electronic equipment at the recording site can be picked up and mixed with the PCM data. This can cause dropouts (loss of data) during playback. The low frequencies are easily removed by filtering but higher frequencies that lie in the same range as the data cannot be removed by filtering. Methods for dealing with this problem have been worked out with some success. The work has just started. Some of the results are described here.
• #### A REVIEW OF THIRTY YEAR’S DEVELOPMENTS AND RESEARCHES ON UNCODED QPPM SYSTEMS

In recent years the researches and applications of QPPM systems in telemetry have drawn much attention, but there are still some problems to be clearified and solved. In this paper we reviewed the classical literatures on un-coded QPPM systems which were published in the past thirty years. After analysing the conclusions and related derivation presented in these publications, we got: 1) M.J.F, Golay and JRA Jacobs stated that the QPPM’s efficiency ß may indefinetely approach Shannon theoretical limit with as small error probability as desired as soon as one can appropriately choose the parameters of the system. In our opinion, this conclusion cannot hold true. In fact, the efficiency curve ß = F(α) of QPPM is only similar in form to the Shannon theoretical limit and there is still a large difference. 2) In past 30 years Golay and the others analysed merely the relation between the word error probability PWE and the efficiency ß , They didn’t study the relation between the bit error probability PBE and ß . Some authors regarded QPPM’s PWE as being equal to other digital system’s PBE, and concluded that QPPM is better than the other systems. We consider that this is not appropriate. 3) In order to remedy the untouched problem, we derived the relation PBE =F(α) of QPPM system. As it is seen from these relation curves that the required α of QPPM is 4.CdB~4.4dB more than the ß of coherent detection PSK system when PBE=10^-4 and α varries from 2 to 100. (ie. the efficiency of QPPM is worse than PSK.)
• #### S-BAND ACQUISITION AND TRACKING SYSTEM (SATS), WSMR SYSTEM FOR SPACE SHUTTLE ACQUISITION

The requirement for WSMR to independently acquire and track the NASA Space Shuttle presented WSMR with one of the basic problems associated with missile and air defense systems - acquiring and maintaining a precision track of an incoming target. The popular solution is to use two radars--a broad beam for acquisition and a narrow beam for precision track. The WSMR solution is the S-Band Acquisition and Tracking System (SATS) which uses two existing passive telemetry trackers (J-10 and J-67) in conjunction with WSMR precision track radars. The existence of an S-Band transmitter in the Shuttle made the use of the Telemetry trackers possible.