13. Linearity

A major disadvantage of the active antenna is that no spatial filtering can be applied to the incident signal before it enters the module. The radiating element functionally has a very open radiation pattern (the beam is formed only after the signals have passed through the modules) and picks up signals from all directions.

The receive channel in each module must therefore be dimensioned for the full dynamic range of all incident signals, without creating intermodulation between signals.

The analysis prior to defining the linear dynamics of the receiving channel involves :

• identification of the nature of the signals likely to be picked up during normal operation of the antenna, whether they are echoes of the transmitted signal or signals of various external origins. Their amplitude, frequency...