In order for a narrowband phased array to be coherent channel to channel, what is the maximum timing jitter that can be tolerated between channels? I assume there can be a constant timing error between channels because this can be calibrated out, but randomly varying timing errors between channels are another matter.
From a naive mathematical perspective, I would assume the channels need to be synced to a small fraction of the wavelength of the carrier (i.e., within a few degrees of phase error at most). This would make it increasingly difficult to build phased arrays at higher frequencies (even ignoring the size and spacing of the antenna elements!). At 5 GHz for example, the time jitter between channels would have to be less than 5 picoseconds (9 degrees phase error) under this assumption.
Is there something I'm missing, or hardware tricks people employ to get around this that I'm not understanding?