This study employs characteristic mode analysis to investigate a defected ground antenna for multiband applications. The antenna structure incorporates three U-shaped slots in the ground plane, forming a defected ground structure. The microstrip line is exclusively present on the front side plane. The antenna is printed on a substrate made of a ceramic-filled PTFE composite with a size of 20 mm × 21 mm × 0.76 mm and a dielectric constant of 3. The proposed antenna is analyzed using the characteristic mode analysis based on the method of moment and simulated by an electromagnetic simulator based on the finite element method. A multiband antenna is fabricated and tested to validate the proposed antenna performance. The simulation and measurement results reveal that the antenna exhibits good input impedance bandwidths of S11 ≤ - 10 dB that extend from 2 to 12 GHz with three bands around the operating frequencies (2.96, 6.06, and 8.03) GHz.
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