UltraWide Band Monopole Patch Antenna for Multiple Resonance

Hi every one, I have one question about UWB.
I want to ask that why there are multiple resonance in UWB monopole patch antenna with a finite ground plane? What is the purpose of finite ground plane? What is the reason that we get multiple resonance? Any link, suggestion, answers will be very helpful.
THANK YOU.

The radiation pattern for the monopole antenna is strongly affected by a finite sized ground plane while the impedance of a monopole antenna is minimally affected. You can get lots of information from journals at IEEE Xplore.