The reason for the extremely narrow
bandwidth of the patch antenna is its ground plane.
Whenever you place a ground plane close to a radiating
system, the bandwidth goes down. You can see this
by checking any antenna book, when they compute
the equation for the dipole impedance above a ground
plane: there is a graphic that shows in the x-axis
the distance from the gnd plane (related to the
wavelength, it is normalized) versus the impedance.
You ll see that for small distances the derivative
of the impedance is very high, which means, very
small changes of frequency result in great changes
in the impedance, i.e., the bandwidth is narrow.
I am pretty sure balanis book contains this picture.
For the way to excite this other mode in a patch
antenna, I sincerely do not know. I dont remember
having seen this before in the literature.