Uniplanar Log-Periodic Slot Antenna Fed by a CPW for UWB Applications

A coplanar waveguide-fed uniplanar log-periodic slot antenna suitable for use in the ultra-wideband radio systems is presented. The in-band impedances and radiation performances are quite stable and satisfactory. A rejected narrow frequency band is further obtained within the wide bandwidth by inserting a pair of metallic stubs into two vertical slots of the proposed antenna. Experimental results reveal that the stub pair provides significant attenuation in the desired notched band but has little effect on the antenna operation outside of the notch. By means of a normalized antenna transfer function, the time-domain characteristics of the proposed antennas are also investigated. The transient responses show that the designs with and without the notched band are both acceptable for the pulsed systems.