Page 43 - Fundamentals of Radar Signal Processing

FIGURE 1.3 One-way atmospheric attenuation of electromagnetic waves.
(Source: EW and Radar Systems Engineering Handbook, Naval Air Warfare
Center, Weapons Division, http://ewhdbks.mugu.navy.mil/)

Lower radar frequencies tend to be preferred for longer range surveillance
applications because of the low atmospheric attenuation and high available

powers. Higher frequencies tend to be preferred for finer resolution, shorter
range applications due to the smaller achievable antenna beamwidths for a
given antenna size, higher attenuation, and lower available powers.
Weather conditions can also have a significant effect on radar signal
propagation. Figure 1.4 illustrates the additional one-way loss as a function of
RF frequency for rain rates ranging from a drizzle to a tropical downpour. X-
band frequencies (typically 10 GHz) and below are affected significantly only

by very severe rainfall, while millimeter wave frequencies suffer severe losses
for even light-to-medium rain rates.