Designing Microstrip Ring Resonator

Hello Experts,
I want to design a Microstrip Ring resonator on Ansoft HFSS; using Roger duriod 5880 substrate for my project
εr=2.2,
tand=0.0009,
Zo=50 Ω,
h=787um,
t=17.5um
at 1GHz,
What are the basic formulas for the MS Ring-resonator; I have found some literature on MS-line, but did't get for MS-Ring resonator,
How we can calculate mean radius, coupling gap, couplers length and what will be the dimensions of Microstrip structure (its length and width).
Can anyone help me by sharing; Basic Designing steps & formulas even with related literature, tutorial or sample-design sot it will be more helpful to me

Thanks guys!

The book that you have to read is: Microwave Ring Circuits and Related Structures, by Chang, Hsieh.

Thanks Vfone; using this i got mean radius but still i haven't know how to calculate the Coupler's width and its length? also its coupling gap?
Actually Im using ring of 1mm width with mean radius = 35mm; any suggestion?

On the net you can find a lot of equations for coupled lines or gap capacitors.

http://qucs.sourceforge.net/tech/node79.html

Have to know that, usually the range value of a gap capacitor is somewhere between 0.05pF and 0.5pF