Design of a Low-Profile Broadband Rectangular Slot Antenna with Dual Resonances

In this paper, a low-profile broadband rectangular slot antenna with dual resonances respectively centered at 1.56 GHz and 1.8 GHz is proposed. A rectangular
$\lambda/4$
slot is etched on a flat conductive plate, which helps to obtain the broadband operation by choosing a proper slot structure and feed position. Dual resonances can be seen as the superposition of a
$\lambda/4$
slot mode and a dipole mode. For the final antenna design, simulated
$\vert \boldsymbol{S}_{11}\vert$
below -10 dB is from 1.37 GHz to 2.03 GHz (42.3%), and the maximum gain of 4.3 dBi and 4.9 dBi can be obtained at 1.56 GHz and 1.8 GHz, respectively.