A new defected ground structure (DGS) with tunable working frequency and reconfigurable bandwidth is proposed in this paper. The prototype combines the conventional DGS with T-shaped patch featuring narrow bandwidth and two such units located symmetrically featuring wide bandwidth. The proposed structure is designed, simulated and measured. By embedding two reversely-set PIN diodes and four varactors, the proposed structure achieves a narrow bandwidth with a tuning range of 21.1% and a wide bandwidth with a tuning range of 24.6%. In comparison, the bandwidth (-10 dB) is about 13.6% for the narrowband state and 49.2% for the broadband state, where an approximately 4-times extension is obtained.
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