A Compact Broadband Capacitively-Loaded Antenna for UHF Application

In this work, a modified capacitively loaded antenna has been designed and fabricated. The desired capacitive impedances are achieved by fixing the space between the conductor rings with dielectric materials. Because the performance of the antenna is affected by the thickness of the dielectric rings, Chebyshev function is applied in this study. The antenna input impedance is mainly controlled by the length of the conical matching network, and the additional size reduction can be achieved by current distribution on the antenna. The lowest limit of the operating bandwidth is improved about 80 MHz in the lower frequency region, compared with the conventional antenna. The broadside radiation patterns of the proposed antenna are enhanced. Also, the size of the antenna is less than a third of the conventional antenna. The measured results show that the proposed capacitively loaded antenna can be applicable to wireless communication systems requiring the wideband operation.