A novel dual-band frequency tunable slot antenna with constant frequency ratio

In this paper, a novel dual band frequency tunable slot antenna using varactors is presented. By varying the bias voltage of the varactors, the length of the slot is tuned equivalently, thus both the lower resonant frequency and the higher resonant frequency can be tuned simultaneously with a constant frequency of f₂/f₁. The first resonant frequency can be tuned from 1.36 GHz to 1.52 GHz while the second resonant frequency can be tuned from 2.12 GHz to 2.63 GHz, as shown by measured results. The achievable frequency ratio approximately remains unchanged within range of 1.56 to 1.73 over the whole tunable range. Compared with the higher band tuning range, the lower band frequency can be considered as constant over the whole bias tuning range. The radiation pattern directions approximately remain the same over the whole voltage tuning range for both band.