How to make subplot title window wide

Hi,

I'm working with matlab 2017b. I have a figure with a series of 2 subplots : subplot(2,1,1); and subplot(2,1,2)

I'm trying to add a common title to both subplots by using the 'suptitle' function. The title seems to be very narrow. I would like it to be window wide

Any help on how to to this?