Antenna Factor Calculations And Deviations

In recent years, the use of a term called "Antenna Factor" in EMC and spectrum pollution work has become very important. There has been a great need for measuring field intensity and/or power density as accurately and conveniently as possible.

Classically in RFI/EMI measurements, the use of antenna factors is very common. These antenna factors were, by definition, the conversion of two-terminal receiver voltages to field intensity. This is a very convenient term, particularly when expressed in decibels, and the receiver measures in dB above 1µ volt. Historically, antenna factors were supplied by equipment manufactures, or in some cases, designated in military specifications. In many cases, these factors were used incorrectly because the user did not understand fully the mathematical significance of the antenna factor. It is the purpose of this paper to establish the relationship of antenna factor and antenna gain.

Antenna gain is a common term utilized by antenna design engineers as well as communication electronic system designers. The gain is the ratio of the power density produced by antenna, at a certain range in a certain direction, to the average power density at that range.

The recent deployment of computer controlled receiving systems with analysis capable capabilities has added a new need for examining the antenna factor. The desired data output from such systems is usually a field intensity expressed in volts per meter as a function of frequency. From the standpoint of strictly application of antenna factors it would seem an easy test to store the antenna factor as a “look up table” in the computers core memory; however as we shall see, it may not necessarily be the most cost effective or the best utilization of computer memory.