Consider a half-wavelength microstrip patch antenna at resonance on an electrically thin substrate (thickness a small fraction of a wavelength).
The radiated power is dependent on the voltage at the end of the patch and the patch width and is independent of the substrate thickness. If we hold the patch width and voltage constant and decrease the substrate thickness we increase the stored reactive power, hence increase the Q and decrease the bandwidth. To understand the basic relationship between the radiated power and the voltage/patch width, look up the 2 slot model of the patch.
I couldn't find a simple paper explaining it, but this would be a start:
Microstrip antenna technology
Carver, K.; Mink, J.;
Antennas and Propagation, IEEE Transactions on
Volume: 29 , Issue: 1
Digital Object Identifier: 10.1109/TAP.1981.1142523
Publication Year: 1981 , Page(s): 2 - 24