Gain restoration after Doppler filtering

Automatic gain control in a pulse Doppler radar receiver is provided after Doppler filtering by a gain restoration system which embodies dynamic correction based on variable returns from clutter and targets. The radar uses a digital fast automatic gain control (FAGC) with a technique known as block adaptive signal regulation (BASR). This technique evaluates all the time samples in a range gate before they enter the fast Fourier transform (FFT) circuit. The invention of this disclosure feeds the information regarding the number of BASR shifts, N, forward to the output of the FFT as a function of range gate. In this way the gain-corrected amplitudes are available for target centroiding. The concept of dynamic FAGC correction based upon the amplitude of clutter and target returns avoids the problems encountered when the system is used in an urban area or with a narrow clutter notch filter. In the past, such operation has resulted in a loss of detectability on small targets in the presence of large targets. However, the gain restoration system described herein feeds the information regarding the number of BASR shifts, N, forward to the output of the FFT as a function of range gate.