This block corrects for the gain difference among the interleaving sub-RF-ADCs. Any residual difference results in spurious signal at +/-fin + (k/N)*Fs, where Fs is the sample rate of the RF-ADC, N is the number of sub-RF-ADCs, and fin is the frequency of the input signal. The GCB requires the presence of an input signal. The minimum power of this input signal is -40 dBFS. Signal bins at f = k*Fs/(2N) are ignored and do not count towards the signal power. This block should be in the freeze mode whenever the input signal power drops below -40 dBFS for longer than 100 μs.