From Radar Design Principles: Signal Processing and the Environment, Second Edition

F. E. Nathanson

J. P. Reilly


Meteorological phenomena have two major effects on radar: the signals are attenuated by clouds, rain, snow, and the atmosphere itself; a relatively large signal is reflected from raindrops, hail, and snowflakes. [1] Attenuation becomes quite significant above X-band (9300 MHz), but backscatter from snow and rainfall generally dominates the detection and tracking problem at frequencies down to L-band (1300 MHz). To compound the problem, the backscatter spectrum from precipitation and chaff is broadened because of wind shear, vertical fall rates, and air turbulence, all of which limit the ability of Doppler processors to separate targets from clutter on the basis of their relative velocities. The backscatter coefficient of chaff dipoles is shown to have much less dependence on the carrier frequency than precipitation echoes, but both have similar amplitude and spectral distributions. The equations and numerical values in this chapter apply to monostatic radars with linear polarization.

[1]For general references see NASA Publications [361] [239] Atlas, "Advances in Radar Meteorology" [25], Battan, Radar Meteorology [48], and Doviak and Zrinc [187].

6.1 Standard Atmospheric Attenuation

Atmospheric attenuation has been treated by L. V. Blake and in NASA publications [2391 [361]. Figure 6.1 from Blake shows the normal atmospheric attenuation through the entire troposphere. The attenuation for a horizontal beam at sea level as a function of range and frequency is shown in Fig. 6.2. Numerous other curves are given in the references. The attenuation coefficient per mile at sea level can...

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Radar clutter is defined as unwanted echoes, typically from the ground, sea, rain or other precipitation, chaff, birds, insects, and aurora [183]. This chapter covers two bistatic clutter topics:...

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