Design of an omnidirectional triple band bent-fork shaped microstrip monopole antenna for multiband applications

The design of microstrip monopole antenna with triple band operation is presented in this paper. In the proposed structure, a novel modified bent-fork shaped radiating element with different arms lengths is utilized in order to generate the multiband functionality, and moreover in order to improve the input matching quality of the antenna at all its various operating bands which are spread in a vast frequency range, a modified stepped feed-line is employed. The measured impedance bandwidth for 10 dB return loss is spread in frequency ranges of 1.7-2.3 GHz (%30.0), 5.1-5.7 GHz (%11.1), and 7.7-8.3 GHz (%7) which is respectively capable of supporting PCS/Bluetooth, WLAN, and X-band applications. The designed antenna has a simple structure with small size of 20×20 mm² while presenting consistent almost fully omnidirectional radiation characteristics at its different frequency bands of operation which is a desirable ability in majority of the related applications.