Theory of Open Loop Resononator

I am currently designing a narrow band filter using Open Lopp Resonator. But unfortunately i didnt get any material on the theory of Open Loop Resonator. Please give me any link or data regarding design of open loop resonator....

http://www.eps.hw.ac.uk/~ceejh3/Jour...%20filters.pdf

In the linked overview, you'll find a basic desription of open loop resonators respectively filters starting on page 13. The paper linked by ckshivaram is dedicated to the more specific topic of slow wave filters.
http://maxwell.uwaterloo.ca/~myu/pub...color-Hong.pdf