3. Spatial filtering and auto-adaptive antennas

3.1 Context

The aim of all imaging methods, whether linear (convolution-based) or high-resolution, is to give the user as faithful an image as possible of his electromagnetic (or sound) environment. However, among the signals present in this environment, some are useful and sought-after, while others are useless or even harmful if they can interfere with the reception of the former: natural or artificial interferers. In radio communications, intermodulation with interfering signals can be considered interference.

The aim of spatial filtering is to modify the antenna's characteristics according to a criterion for optimizing the useful signals: the antenna is no longer a passive organ that is expected to be transparent and faithful, but plays an active role....