...
The design supports a future option to apply delays to each signal path to point the telescope to a specified correlation pointing centre. When that mode becomes available, it will involve the integer sample component of the required delays being applied at the time the using whole-sample shifts as the sub-observation data is assempledassembled, and with the residual fractional delays being applied within the FX engine. The required fractional delay values for each signal path (on 5 ms resolution) are passed to the FX Engine via the prepended metadata block written to the input ring buffer. Delays are applied by multiplying the frequency-domain samples of each sub-block by a phase gradient, whose complex gain values are taken from a pre-computed look-up table to increase speed.
...