Q. Explain Position servo in a radar system?

Figure depicts the essential elements of a position servo system. In a radar system, an electromagnetic pulse is radiated from an antenna into space. An echo pulse is received back when a conductive surface, such as an airplane, appears in the signal path. While the antenna is continuously rotated in search of a target, the antenna is stopped when the target is located.

It is pointed toward the target by varying its angular direction until a maximum echo is heard. The position coordinate θ(t) of the antenna is usually controlled through a gear train by a dc servomotor. The motor torque is varied in both magnitude and direction by means of a control voltage obtained from the amplifier output. The control problem is then to command the motor such that the output θ(t) is nearly the same as the reference angular position θr(t). The closed loop can be controlled by a digital controller.