RAdio Detection and Ranging (RADAR)
What is Radar?
Radar Classification
Radar Equation
Radar Noise and Clutter
Radar Jamming
Radar Frequency Bands
Penetrating
Ground Penetrating Radar (GPR)
Synthetic Aperture Radar (SAR)
InSAR
Lecture Summary

1) Surface Clutter – Ground or sea returns are typical surface clutter. Returns from
geographical land masses are generally stationary, however, the effect of wind
on trees etc means that the target can introduce a Doppler Shift to the radar
return. This Doppler shift is an important method of removing unwanted
signals in the signal processing part of a radar system. Clutter returned from the
sea generally also has movement associated with the waves.
Volume Clutter – Weather or chaff are typical volume clutter. In the air, the most
significant problem is weather clutter. This can be produced from rain or snow
and can have a significant Doppler content. 
3) Point Clutter – Birds, windmills and individual tall buildings are typical point
clutter and are not extended in nature. Moving point clutter is sometimes
described as angels. Birds and insects produce clutter, which can be very
difficult to remove because the characteristics are very much like aircraft.