Terrestrial Land Mobile Radio-Antenna Systems-History and Technical Analysis of the Quarter Wave Monopole Over Finite Ground Plane as a Gain Standard
|Publication Date:||1 December 2010|
In the land mobile service there has historically been no clear relationship between the gain of base station antennas and the gain of mobile antennas. A half wavelength dipole has been used as the basis of the base station antenna gain, and a quarter wavelength monopole over a finite size ground plane has been historically used for the vehicular antenna. This makes it difficult, at best, to analyze and predict the coverage of land mobile communications. For some few years recently, the mobile standard was made a half wavelength dipole, but the difficulty of using that standard resulted in universal rejection by the manufacturers of mobile antennas.1
Some measurements and computations have been made to determine the absolute gain of a quarter wavelength over a finite size ground plane, and they show that it is a function of the frequency and size of the ground plane. But the gain of a half wavelength dipole is a constant 2.15 dBi. And this is a comparison made in free space with no reflections such as are found in the practical land mobile application.
This Bulletin will present the history of the antenna gain standard as used in TIA standards and those of EIA, its predecessor. A review will show what has been done to relate the gain of the half wavelength dipole to that of a quarter wavelength monopole over a finite size ground plane for the land mobile service. From that review it will be shown what is needed to accurately analyze communications coverage in the multipath world of land mobile communications.
1 In 2005 known manufacturers of mobile antennas sold in the United States and Europe were asked by TIA Subcommittee TR-8.11 if they used the present TIA Standard for vehicular antennas. That standard was MINIMUM STANDARDS FOR COMMUNICATIONS ANTENNAS, VEHICULAR ANTENNAS, TIA-329-B-1. It is the only one that tried to use a half wavelength dipole as the gain standard, and every manufacturer stated that they did not use it.