Clutter cancellation

Clutter is defined as echoes from hills, buildings, masts, sea, and noise as marks in the image caused by electronics of the equipment. The goal of clutter cancellation is to remove clutter without destroying rain data.

To illustrate a Doppler filter, we study speed spectra of a bin. That is, Doppler speed of each sample, horizontal axis being speed (towards or away from radar, 0 in the middle). If all samples indicate no speed we know the target is not moving. However, even antenna movements gives some speed. And there are cases when it is raining at the hills.

The next image shows a Doppler spectra from a bin, which contains clutter (speed near 0) and rain moving toward the radar (big hump on the left) as well as some noise (small humps everywhere, seen alone on the right). To find the right settings for the Doppler filter, we can move the red lines closer to each other (less rain data is destroyed) or further from each other (more clutter is canceled).