See the Python reference of this logic brick in
The Radar Sensor works much like the Near sensor, but only within an angle from an axis, forming an invisible cone with the top in the objects’ center and base at a distance on an axis. It is possible to visualize the invisible cone turning on the Physics Visualization. This sensor is useful for giving bots sight only in front of them, for example.
The Radar sensor cannot detect soft bodies. This is a limitation in Bullet, the physics library used by the Game Engine.
The Radar sensor can detect objects “through” other objects (walls, etc.).
Objects must have Physics “Actor” property enabled to be detected.
See Sensor Common Options for common options.
This field can be used to limit the sensor to look for only those objects with this property.
This menu determines the direction of the radar cone. The ± signs is whether it is on the axis direction (+), or the opposite (-).
Determines the angle of the cone.
Determines the length of the cone. (Blender units).