Analysis of Antennas as Components of Broadband and Multiband LMR Systems

This paper describes a method for evaluating the performance of antennas for land mobile radio (LMR) in terms of "bottom line" system performance metrics including sensitivity, VSWR, and transmit efficiency. The method accounts for relevant characteristics of the transceiver and the noise environment. The antenna-transceiver interface is modeled in terms of two-port 8-parameters, facilitating evaluation of reconfigurable and non-Foster matching circuits. As an example, the method is applied to a simple system consisting of an ideal thin quarter-wave (at 453 MHz) monopole, 17 ft of RG-58 coaxial cable, and a TIA-603-compliant analog FM transceiver. Among other findings, this example demonstrates that that the useful transmit and receive bandwidths are not necessarily equal, and that the useful receive bandwidth is limited not only by the antenna's impedance bandwidth, but also by receiver's noise figure, and possibly also by environmental noise. Such insights are useful in the development and optimization of antenna technology intended for use with existing LMR systems.