Antenna Measurement Basics

Antenna Measurement BasicsAntenna Measurement Theory
Introduction to Antenna Measurement

1. Basic Concepts
1.1 ELECTROMAGNETIC WAVES The radiation field from a transmitting antenna is characterized by the complex Poynting vector E x H* in which E is the electric field and H is the magnetic field. Close to the antenna the Poynting vector is imaginary (reactive) and (E,H) decay more rapidly than 1/r, while further away it is real (radiating) and (E,H) decay as 1/r . These two types of fields dominate in different regions in space around the antenna. Based on this characterization of the Poynting vector, we can identify three major regions (Figure 1).

Figure 1: Radiating Regions

1.1.1. Reactive Field This region is the space immediately surrounding the antenna. The extent of this region is 0 < r < λ/2π, where l is