A study on tuning-stub of slot antenna for ultra-wideband applications

This paper describes the increasing bandwidth of slot antennas with simply microstrip feed line design. The lower edge frequency of the first band depends on antenna size and the bandwidth becomes widen due to tuning stub. The effect of tuning stub can expand upper frequency of bandwidth to higher frequency. The higher frequency is defined by the stub shape, and its parameters are adjusted to match impedance of transmission line with 50 ohms. By properly setting stub size, a wide impedance bandwidth of the proposed antenna can be achieved for ultra-wideband applications. We propose the tuning stub at the end of the microstrip line for extending bandwidth over 8.0 GHz. In this case, an impedance bandwidth of the slot antenna with tuning stub is 8.05 GHz from frequency range 2.73 GHz to 10.78 GHz. This bandwidth coverage the requirement standard of IEEE 802.15a of frequency range from 3.1 GHz to 10.6 GHz of bandwidth 7.5 GHz by The Federal Communications Commission (FCC).