A new frequency reconfigurable unequal U-slot antenna is presented in this paper. The U-slot antenna loaded with two lumped variable varactors is capable of 6 different frequencies switching between 2.3 GHz and 3.6 GHz. The small slots in the ground plane are employed for the biasing circuit to minimize the parasitic effects towards the performance of the antenna. It is found that the unequal U-slot fed by an L-shaped feed line can reduce 30% of the size of the conventional U-slot antenna. Moreover, the proposed antenna offers stable radiation characteristics for each operating frequency in the tunable range. The antenna offers a gain of 4.5 dB in average. The designs are verified through both numerical simulations and measurements of an experimental prototype. Details of the antenna designs and measured results are presented and discussed.
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