Frequency-tunable open-ring microstrip antenna using varactor

In this paper, the varactor-loaded open-ring microstrip antenna is proposed. To overcome the inherent characteristics of narrow bandwidth of the open-ring microstrip antenna, the varactor is positioned on the edge of the ring. The frequency is tuned by controlling the DC voltage connected to the varactor. For the simulation model, instead of the real varactor, the discrete capacitor is used. The return loss (S₁₁) from the simulation shows that the resonant frequency is lowered by increasing the capacitance value. This frequency-tuning technique could be used in the many applications such as the frequency-reconfigurable small antenna.