The authors describe a low profile CPW and microstrip-fed half-circle planar monopole antenna with dual rectangular slit, which has similar radiation pattern properties for Ultrawideband applications. In this case, the inserted dual slit on the monopole also leads to enhancing the wide band impedance. The inserted dual slit on the monopole and feeding structures (CPW-fed and microstrip-fed with a dual open-stub) also leads to reducing antenna size and enhancing wideband impedance matching characteristic. The antenna has a low profile of 24mmX 30mmX1mm. The measured bandwidth is from 2.92GHz to 11.7GHz for the return loss less than -10 dB. The proposed antenna also has a peak gain of 4.5dBi.
Ultrawideband (UWB) antenna designs have been increasing substantially since 2002, when the Federal Communication commission(FCC) allowed use of the 3.1-10.6GHz band for UWB communication. In modern wireless communications, miniature antennas are desirable for portable devices as the space available for installation of antennas is limited. The printed antenna is definitely a good choice because of its numerous features, such as light weight, low profile, conformal to the mounting structure, and adaptive to mass production. Actually, the microstrip-fed printed monopole antenna[1,2,3] and a shunt-stub microstrip-fed[4] and slot antenna[5] can achieve wide impedance bandwidth characteristics, respectively. The coplanar waveguide(CPW)-fed [6,7] planar monopole antennas have especially received more attention than others due to its easy realization and simple structure. But the configuration studied in Refs.2, 3, 5 and 6 occupied relatively large area, which may not meet with the requirements for low profile and low cost.
In this article, we investigated a low profile CPW and microstrip-fed half-circle planar monopole antenna with dual rectangular slits, which has a similar radiation pattern property. In this case, by using a microstrip-fed with a dual-stub and a CPW-feed to excite the monopole, the proposed antenna presents a good impedance matching in a wide frequency band. And inserted dual slit on the monopole also leads to enhancing wide band impedance and reducing the antenna profile. The measured bandwidth is from 2.92GHz to 11.7GHz for a return loss of less than -10 dB. The proposed antenna has a high peak gain and low profile characteristics. The calculated and measured results for the ultra-wideband performance and the experimental radiation patterns and gain are also presented.