Miniaturization of UHF Antenna Using a Capacitive Hat and Parasitic Ring

This paper presents a design approach to achieve the operational frequency ranging from 40MHz to 160 MHz with VSWR ≤ 3 and 5 dBi realized gain in prefixed antenna size of 30 cm width and 100 cm height. A body of revaluation (BoR) monopole antenna was optimized with respect to lowest frequency (f_low) for the specified parameters resulting in lowest achievable frequency of f_low = 50.21 MHz. To improve f_low, capacitive hat and parasitic ring are used without changing surface profile of the BoR monopole, resulting in f_low = 40 MHz.