Full digital automatic gain control device and method

The invention discloses a full digital automatic gain control device and a full digital automatic gain control implementation method. The method comprises the following steps of: detecting a highest significant bit W of an input digital signal h, and determining the direction and the number of bits of shifting operation according to a difference N between the highest significant bit W and a reference value B; carrying out N-bit shift operation on the input digital signal h, and carrying out the N-p bits shift operation on the input digital signal r, wherein the p is a positive integer of more than or equal to 0; performing fast Fourier transform (FFT) on the shifted input digital signals r and h respectively, so as to obtain a frequency-domain digital signal FFT (r) and a frequency-domain digital signal FFT (h) respectively; detecting a maximum value of the frequency-domain digital signal FFT (h), and using the maximum value as an address to obtain a gain coefficient K through table lookup; and multiplying the frequency-domain digital signal FFT (r) and the frequency-domain digital signal FFT (h) by the gain coefficient K respectively to obtain required output digital signals R and H. By the device and the method, the two paths of input digital signals r and h can be adjusted simultaneously, robustness is good, and complexity for implementation is low.