Title page for ETD etd-12102012-171705


Type of Document Master's Thesis
Author Kumar, Akshay
Author's Email Address akshay2@vt.edu
URN etd-12102012-171705
Title Measurement of Antenna Performance in Analog LMR Systems Using PL Tone Analysis
Degree Master of Science
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Ellingson, Steven W. Committee Chair
Beex, A. A. Louis Committee Member
Clancy, T. Charles Committee Member
Keywords
  • Antennas
  • Antenna performance
  • in-situ measurements
  • LMR systems
  • RF SNR
  • Public Safety Radio
Date of Defense 2012-11-30
Availability restricted
Abstract
We are interested in measuring the in situ antenna performance in analog land mobile radio (LMR) FM systems. The gain (efficiency and directivity) and self-impedance of an antenna sufficiently characterize its performance and a number of traditional methods exist to measure these quantities. However it is hard to do antenna gain measurements using these methods. Furthermore, it turns out that volumetric antenna gain measurements are not quite relevant for understanding in situ performance. In this thesis, we present a novel approach for directly measuring the in situ performance of antennas in analog LMR systems. The procedure involves receiving an FM signal simultaneously using the antenna under test (AUT) and a reference antenna. Both received signals are demodulated to audio using separate but identical receivers. Then a convenient method for characterizing the audio signal quality is to analyze the private line (PL) tone. The PL tone signal-to-noise ratio (SNR) is calculated by measuring the power of the tone relative to the sub-audio noise power. The PL tone SNR for both antenna systems is compared as it provides a ``bottom line'' evaluation of the antenna performance. The audio SNR can also be mapped to RF SNR using a theoretical method. From simulation and experimental studies, we conclude that the RF SNR estimated using this technique is within 0.5 dB of the actual value for RF SNR values between +3 and +36 dB. Finally, we demonstrate this procedure in actual in situ LMR antenna measurements.
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