I have a couple of signals(sinal 1, signal 2, ...).And I have an other signal named signal k .How can I find out that which signal has the least phase shift with Signal k??

my signals: signal 1 , signal 2 , and..... my an other signal: signal k

So now I want to find out the phase shift between (signal 1 and signal k),(signal 2 and signal k), (signal 3 and signal k) and...

In other words,I want to find the least phase shift.

* my signals are in time domain.but maybe you need to transfer them to frequency domain. Thank you so much.