Device and method for adjusting loop filter gain in automatic frequency control

A device and a method for adjusting a loop filter gain in an automatic frequency controller are provided to optimize performance and to maintain a lock state of the automatic frequency controller by varying a total loop bandwidth of the automatic frequency controller according to a velocity variation quantity. A method for adjusting a loop filter gain in an automatic frequency controller includes a velocity measuring unit(151), a loop filter gain control unit(152), and a loop filter gain unit(153). The velocity measuring unit(151) measures a velocity change according to the movement of a terminal. The loop filter gain control unit(152) adjusts a loop filter gain value according to the velocity change received from the velocity measuring unit(151). The loop filter gain unit(153) multiplies and outputs the loop filter gain value received from the loop filter gain control unit(152) by a frequency error value. The velocity measuring unit(151) extracts a Doppler frequency generated according to the measured velocity change.