monopole antenna using CST

hye..my monopole antenna is designed with 2.45GHz. the width is 3mm and the length is 56.44mm.My problem is i can't get the resonant frequency 2.45GHz and the surface current seems radiate only a half way on monopole antenna.can someone help me how to exact equation for monopole antenna and the weird surface current..

First of all, the length of the monopole should be equal to lamda/4 which is equal to 29.5mm at 2.45 GHz. How did to get the value of 56.4mm and do you have a ground plane beneath the monopole antennna ?

hye sv..thanks for reply..actually i using h=lamda/4 which give a result height=30.6mm.but i'm confused when i substitute the epsilon 4.7 into lamba equation, i got 56.44mm for full wavelength.after that,i run a simulation using cst and i dont get the resonant frequency and my total radiation is -20db.i dont know what is wrong with my design.