Abstract: This paper proposes a novel approach to reduce size and increase the impedance bandwidth of microstrip UWB (Ultra-Wideband) antenna, when using a thick substrate, so that it can be used for WPAN application, especially for mobile and portable devices.The application of gap-coupled capacitive feeding mechanism for achieving UWB with microstrip antenna has also been proposed.. The proposed antenna is capable of operating over a bandwidth (6.4GHz-10.4GHz) as allocated by FCC (Federal Communications Commission), suited for an UWB (Ultra-Wideband) application. Although coaxial probe feed is one of the most popularly used feeding mechanism for thick substrates, but the inductance of the probe might create an impedance mismatch, which needs to be compensated by introducing a capacitive feed strip.