Metamaterial-based frequency reconfigurable microstrip antenna for wideband and improved gain performance

A metamaterial-based frequency reconfigurable microstrip antenna is proposed with wideband tuning range and enhanced gain. By co-designing the main reconfigurable microstrip patch unit and the upper-layer located reconfigurable negative-permeability-metamaterial resonant loop, the gain of the resultant proposed antenna is readily improved. The wideband reconfigurability of the microstrip antenna and the metamaterial unit is realized by tuning the capacitance values of the varactor diodes through altering their bias voltages. Furthermore, the effect of different number of reconfigurable metamaterial units on the gain of the proposed antenna is extensively explored, which shows the radiation pattern is largely improved since the electromagnetic energy is more concentrated and directed. Finally, the proposed antenna is fabricated and measured. The experimental results demonstrate that the operating range of the proposed antenna is within 8.6-10.3 GHz, and the reflection coefficient is less than -10 dB, and the gain is above 6 dBi. The radiation efficiency of the antenna is above 85%. The electrical size of the antenna is 0.58 lambda(0) x 0.58 lambda(0). As expected, the proposed antenna has the main advantage of enhanced gain performance, while performing comparable frequency tuning range.