Browsing by Author "Barts, Robert Michael"

Now showing 1 - 3 of 3
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    Statistical modeling and simulation of mobile satellite propagation
    Barts, Robert Michael (Virginia Polytechnic Institute and State University, 1988)
    Land mobile satellite systems that are currently being designed for implementation in the next decade will need to operate in the presence of propagation effects such as vegetative shadowing and multipath that will cause signal fading. This paper discusses the statistical modeling and simulation of the land mobile satellite fading environment. Simple models are developed to approximate the complex analytical expressions for the fade distributions. The Average Path Model, which relates the physical parameters of the vegetation along the path to the propagation model parameters, is verified and shown as a useful model for estimating the propagation parameters. Discrepancies between the VT Propagation Simulator and the analytical models are resolved and results comparing secondary fading statistics from the simulator to measured data are given. Results of a study using the propagation simulator to simulate spatial diversity to combat vegetative fading are given.
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    Stub loaded helix antenna
    (United States Patent and Trademark Office, 1999-11-16)
    A helical antenna having stubs spaced along the helix curve length and extending toward the central axis of the helix, such that the performance characteristics of the antenna, such as gain and circular polarization, are maintained while the size of the antenna--diameter and length--are reduced.
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    The Stub Loaded Helix: A Reduced Size Helical Antenna
    Barts, Robert Michael (Virginia Tech, 2003-10-20)
    This dissertation details the development of a novel reduced size axial mode helical antenna called the Stub Loaded Helix (SLH). The SLH achieves a significant reduction in helix size, both diameter and length, compared to the conventional axial mode helix antenna with only small compromises in performance. The SLH achieves this entirely through the use of a unique geometry. The performance characteristics of the SLH are explored through the use of computer simulations using NEC (Numerical Electromagnetics Code) to study the effects of design parameter variations. Based on those simulations, design guides are developed. The numerical simulations are verified though measurements of experimental prototypes. The program of experimental prototypes included the development of an appropriate impedance matching network for the SLH, which is also detailed.