A co-planar waveguide-fed symmetrical staircase-shaped ultra-wideband antenna is proposed in this work. This antenna consists of three pairs of rectangular notches, two symmetrical C-shaped slots and two pairs of quarter-circular-ring-slits which are etched on the rectangular radiator and ground plane, respectively. By sequentially inserting three pairs of rectangular notches with proper positions, an excellent impedance bandwidth of 1.55-16.95 GHz (166.51%), i.e., a 10.94:1 ratio bandwidth is obtained. The total volume of the prototype is merely 0.239×0.224×0.004λl3, λl wavelength of the free space at the lowest operating frequency (i.e., 1.55 GHz). As a result, wider impedance bandwidth, fair gain and better impedance matching of the proposed antenna are obtained. It is observed that the simulation results are in good agreement with the measurement results. The transmission line model (TLM) of the proposed antenna is presented, and it shows the antenna behavior based on the effect of each element. It is observed that the characteristics of the TLM model are close to the simulation result using the CST simulator. The prototype is successfully implemented, fabricated, and compared with the experimental results.