A Novel Design Method of C-Shaped Slots for Reconfigurable Band-Notched UWB Antenna

A novel design method of C-shaped slots with adjustable effective lengths to achieve reconfigurable band notches in ultra-wideband antennas is proposed in this paper. Its novelty lies in using C-shaped slots to design specific band notches and electrical switches to enable performance reconfiguration. Specifically, the lengths of the C-shaped slots corresponding to the desired band notches are first established, and then PIN diodes are placed at the appropriate locations to connect the C-shaped slots at the same end, thereby overlapping them. Controlling the ON/OFF state combinations of PIN diodes can adjust the effective lengths of these C-shaped slots. As a design example, two PIN diodes are incorporated into a circular patch antenna to form three C-shaped slots with different effective lengths. Simulation results show that by changing these PIN diode state combinations, the proposed antenna can reconfigure between UWB (2.89–15 GHz) and three specific single-band notches: the S-band (2.74–3.36 GHz), the WiMAX band (3.45–3.97 GHz), and the C-band (4.47–4.98 GHz). Throughout the entire operating band, it can also sustain favorable radiation patterns (“8”-shaped in the E-plane and omnidirectional in the H-plane) and steady gain (up to 4.8 dB). The measured results of its prototype agree well with the simulated ones. Furthermore, the band-notched mechanism reveals that various ON/OFF state combinations change the effective lengths of the C-shaped slots and reverse the direction of surface currents on both sides of these slots, thereby suppressing electromagnetic wave radiation.