design of a bandpass filter

when we design a bandpass filter either interdigital or combline or hairpin using tapped line feed input...since the tapped feed is 50 ohm and resonator impedance is greater than 50 ohm so there is a mismatch in impedance .....whether we can make the resonator impedance also equal to 50 ohm or not? i refered to text book of lancaster and hong and i have the examples also why always the resonator impedance is greater than 50 ohm?

Hi,
Generally your filter impedance should be greater than the feed impedance .any way the impedance will be matched once u change the feed position .See Nadeem paper for mode details .

can u plz send the nadeem paper for me
bcoz i have one basic question for filter why the resonator impedance is high when we go for narrow band filters and why the resonator impedance is low when we go for wide band filter?

hi
the position of feed line gives u the best matching .for band pass filter ushould making coupling betwwen resonator and feed line wekely not strong coupling
best regard