This paper reports a novel, cost effective, and compact ultra-wideband (UWB) antenna for applications in an unlicensed-frequency band of 3.1-10.6 GHz. To achieve the UWB operation, a novel concept of annular shapes, circular slot combinations, and partial ground is employed. Furthermore, the proposed antenna with novel configuration occupies an attractive size of only 18×12 mm2 which allows compatibility with portable UWB application devices. This flower-horn shaped UWB antenna is printed on a cost-effective FR-4 substrate, which exhibits a dielectric-constant of 4.4 and a loss-tangent of 0.019. The fabricated prototype is experimentally tested, and measured results validate the design approach of presented UWB antenna. The measured results confirm its UWB characteristics covering 3.1-11.2 GHz with S11 ≤ -10 dB. Also, a maximum peak-gain of 5.05 dBi at 9 GHz and a minimum radiation-efficiency of 94.35% are noted in the full operating-band. A good agreement has been obtained between the simulated and measured results in terms of reflection-coefficient, gain, radiation-efficiency, radiation patterns and group delay which confirm the suitability of suggested small printed antenna for the intended UWB applications.