Delay-DPC

Before the signals from the different antennas can be combined in any of the back-ends, they have to be delay corrected to compensate for the different travel time of the radio frequency signals reaching the antennas due to the relative location of the antennas and the length of optical fiber between the antennas and the correlator, called the geometric delay and fixed delays respectively. This unit compensates these delays. The unit also samples the given data from the ADCs by writing the data into the memory with Nyquist sampling rate ($32/2^n$ MHz, where n=0 to 7) which is twice the bandwidth selected for the baseband output signals. Since the geometric delay changes with the source hour angle, the unit updates this differential delay periodically.