This paper introduces a novel four-port multiple-input multiple-output antenna constructed with a conical surface geometry that surmounts the constraints of prior models intended for ultrawide-band applications, such as missile guidance applications. Each orthogonal element spans a stepped rectangular patch fed by a tapered microstrip line, offering polarization diversity. This structure shrinks the dimensions of the antenna to 42 × 42 mm2. A minuscule pair of non-driven elements on the rear Reflective surface functions as a decoupling element Mediating adjoining ports to further boost functionality. Curiously designed in the shape of a windmill and spinning cross, the tapes elevate the isolation. The proposed dual-band monopole antenna was designed on a compact FR4 substrate with a permittivity of 4.4 and a thickness of only 1 mm. Measurements revealed an impressive impedance bandwidth from 3.5 GHz to well beyond 16 GHz along with isolation exceeding 20 dB between the two ports. The envelope correlation was a negligible 0.0002 while diversity gain reached a hearty 10 dB across the band. Group delay differed by less than 1 ns throughout. Though other designs may perform better regarding one or two of these metrics, our antenna achieves a deft equilibrium of bandwidth, size, and isolation unlike anything yet reported. While demonstrating quite pleasing quasi-omnidirectional radiation over its broad operational range, making it well-suited for an array of emerging wireless applications, notably in minimized gadgets, a more nuanced evaluation of its design is still warranted to realize its potential for the networks of the future fully.