narrow band bandstop filter with high rejection

I am now designing a bandstop filter with the requirement:
pass band: DC-868;882-2500MHz
reject band :870-880MHz
rejection: 80dB.
I have followed the method of filter bible. A main stripline.
every 1/4 lamda I place a resonator coupled to the stripline.
the resonators are coaxial resonators. and I strictly calculate the
differenctial coefficient of reactace of each resonator over frequency.

But the result greatly dissappointed me.the reject band is too wide.
and the 868Mhz and 882MHz points are all in reject zone.

any tuning can not change the situation.

I guess that perhaps it is beacause of the Q factor of each resonator is too low.
so each reject peak is not so sharp.and then s21 is not sharp.

who can give me any advices?thanks

Liu Yun