Planar ultrawideband antennas with improved realized gain performance

The design nuances and associated performance characteristics of two printed planar ultrawideband (UWB) antennas are reported. The designs achieve improved broadside-realized gains, particularly at the high-frequency side of the UWB band. An arc-shaped slot is etched into the radiating patch of a standard compact elliptically shaped UWB monopole antenna. The resulting parasitic element is engineered to produce its fundamental resonant mode in such a manner that a more compact overall design is realized and the broadside-realized gain in the upper UWB frequency range is improved while maintaining impedance matching without any significant changes to the original design parameters. In agreement with simulations, a 61.7% reduction in size from previous designs is demonstrated with more than a 6 dB increase in the realized gain near 10 GHz. To further improve its high-frequency characteristics, a multimode-resonator filter consisting of a single-wing element is combined with the slotmodified UWBantenna. The filter is first designed, fabricated, and measured to demonstrate that it produces the predicted appropriate transmission characteristics throughout the UWB band. The design integration of this compact filter is then presented and the resulting performance characteristics of the overall antenna system illustrate its advantages. The simulated and measured results are in good agreement. They indicate that the integrated design possesses sharp frequency cutoffs at both edges of the UWB passband, as well as strong upper stop-band attenuation. As a consequence, a 2.12 dB further increase of the broadside-realized gain values is demonstrated near 10 GHz.