Miniaturized Dual-Band CPW-Fed Annular Slot Antenna Design With Arc-Shaped Tuning Stub

The design of a miniaturized dual-band CPW-fed annular slot antenna with arc-shaped tuning stub is proposed. The proposed feeding structure, which includes the arc-shaped tuning stub and a 50- transformer, is connected to the extremity of the CPW fed-line, achieving the dual-band input impedance matching. The return loss of the proposed design exhibits that two wide operating bands are over the bandwidths of 30.8% and 24.0%, respectively. By modifying the angle of the arc-shaped tuning stub, the first-higher order resonant mode can be shifted to the lower frequency band to combine with the fundamental mode of the annular slot, achieving the broadband operation with the bandwidth of 3048 MHz (78.4%). Moreover, the miniaturized design indicates an embedded strip is protruded from the ground plane into a slit, revealing the center frequencies of two resonant bands from 2752 to 1738 MHz (size reduction 60%) and 5022 to 3760 MHz (size reduction 44%), respectively. Two resonant bands of the prototype show the broadside radiation patterns with the maximum peak antenna gains of 3.8 dBi and 5.1 dBi, respectively.