Radomes are generally made of dielectric materials which are characterized by their dielectric constant, loss tangent, and various other electrical parameters. Dielectric materials have a characteristic impedance of where is the dielectric constant relative to free space. The impedance of free space is .

When an electromagnetic wave in free space impinges upon a dielectric material at normal incidence as shown in Figure 2, the reflection coefficient is . Since is less than , the reflection coefficient is negative which means reflected wave is 180° out of phase with the incident wave. When the wave hits the free space boundary on the other side of the dielectric, the numerator reverses and . [2]

Figure 2: When an electromagnetic wave hits the dielectric interface, part of the wave is transmitted through the dielectric material, and the rest is reflected.

Several radome configurations are used to minimize RF reflections, including electrically thin, half-wave, A-sandwich, C-sandwich and others [3]. The best configuration for a particular application depends on the mechanical requirements and operating frequency.