Call number: LD2668 .T4 1931 P41

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper analyzes the feature of frequency stability and modulation of airborne telemetry transmitters. According to the characteristic of telemetry information transmission, several methods for frequency stabilization and modulation are briefly compared. Emphasis is given to discuss frequency dividing phase- locked frequency modulation and on-off keying modulation and FM/on- off keying double modulation. With the view of raising frequency stability and modulation sensibility, extending the linear range of modulation, the contradiction between frequency stabilization and modulation should be coordinated properly. In addition, a compatible method between conventional telemetry channel and super fast signal telemetry channel is introduced. A satisfactory result has been acquired with those views and methods used in engineering application.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 92-93). Also available via the Internet.

F.P. Zaffarano and W.C. Galloway. / "May 1, 1947." / Bibliography: p. 28. / Army Signal Corps Contract No. W-36-039 sc-32037.

A power system should always operate in a balanced and stable condition at its designed frequency. Any significant upset of this balance will produce a change in the power system frequency. It is the responsibility of the monitoring and protective devices to detect and restore the system to the equilibrium operating condition at the nominal frequency as soon as it is practical to do so. An accurate measurement of both frequency deviation and rate of change of frequency will greatly facilitate the restoration process. In this thesis, a recursive algorithm for precise frequency and rate of change of frequency measurement is presented. The algorithm consists of three major steps. First, a rough frequency estimation for a data window is computed using a second order least error square approximation on the phasor angles of the input waveform. Then, a resampling based on the rough frequency estimation is carried out, followed by another second order least error square approximation to obtain the final results. The results of simulations using this approach are provided. / Master of Science

M. S.

Quadrature amplitude modulation (QAM) is a highly bandwidth efficient transmission technique for digital communications. It makes use of multiple signal phase and amplitude levels to carry multiple bits per symbol. This requires accurate and robust carrier phase and frequency estimation in the receiver. / Thesis (PhDElectronicEngineering)--University of South Australia, 2002

This thesis proposes a method and develops a mathematical model for determining the effects of hydro power plants&rsquo / governor settings on the Turkish power system frequency. The Turkish power system suffers from frequency oscillations with 20 &ndash / 30 seconds period. Besides various negative effects on power plants and customers, these frequency oscillations are one of the most important obstacles before the interconnection of the Turkish power system with the UCTE (Union for the Coordination of Transmission of Electricity) network. Taking observations of the system operators and statistical studies as an initial point, the effects of hydro power plants&rsquo / governor settings on the Turkish power system frequency are investigated. In order to perform system wide simulations, initially mathematical models for two major hydro power plants and their stability margins are determined. Utilizing this information a representative power system model is developed. After validation studies, the effects of hydro power plants&rsquo / governor settings on the Turkish power system frequency are investigated. Further computer simulations are performed to determine possible effects of changing settings and structure of HPP governors to system frequency stability. Finally, further factors that may have negative effects on frequency oscillations are discussed. The results of study are presented throughout the thesis and summarized in the &ldquo / Conclusion and Future Work&rdquo / chapter.

Terahertz (THz) heterodyne receiver systems are required by NASA to monitor gas concentrations related to the Earth's ozone depletion. To this end, NASA needs compact, solid state, tunable THz local oscillators. THz LOs have been developed using three means: 1) All-electronic LOs using mixers in combination with Gunn oscillators, 2) Hybrid Photo-electronic LOs using a cw analog of the Auston switch, and 3) All-photonic THz LOs using coherent sources, such as vapor lasers or solid-state Quantum Cascade Lasers, and down converting lasers using nonlinear crystals. In this dissertation, we began with two frequency stabilized Nd:YAG lasers, locked to a common reference cavity, as a starting point to having a stable input into a nonlinear optical frequency conversion system. Following this, we explored the nonlinear crystals useful for THz generation, and the phasematching schemes that could be employed by each. We concluded by settling on highly insulating III-V semiconductor crystals as the proper choice of nonlinear element, and put together a new phasematching method that is most useful for them.

This thesis presents a novel approach for a power system to find a practical power flow solution when all the generators in the system have hit their real power output limits, such as some generator units shutting down or load outages. The approach assumes the frequency of the system is unable to be kept at the rated value (usually 60 or 50 Hz) and accordingly, the generator real power outputs are affected by the system frequency deviation. The modification aims to include the system frequency deviation as a new state variable in the power flow so that the power system can be described in a more precise way when the generation limits are hit and the whole system is not operated under the normal condition. A new mathematical formulation for power flow is given by modified the conventional power flow mismatch equation and Jacobian matrix. The Newton – Raphson method is particularly chose to be modified because Newton – Raphson method is most widely used and it is a fast convergent and accurate method. The Jacobian matrix will be augmented by adding a column and a row. Matlab is used as a programming tool to implement the Power Flow for Long Term Frequency Stability (PFLTFS) method for a simple 4-bus system and the IEEE 118-bus system. And PSS/E Dynamic simulation is used to verify the steady state solution from PFLTFS is reasonable. The PSS/E Dynamic Simulation plots are used to analyze the long term frequency response. The PFLTFS method provides a technique for solving an abnormal state system power flow. From the results we can conclude that the PFLTFS method is reasonable for solving power flow of a real power unbalanced system.