Electrically Small Patch Antenna Loaded with Metamaterial

In this paper, the authors present a new planar metamaterial loaded electrically small microstrip patch antenna. The rectangular microstrip patch antenna is loaded by metamaterial using planar square spilt ring resonators (SRRs). The unloaded rectangular microstrip patch antenna resonates at 23 GHz, whereas after loading it by metamaterial, the same antenna resonates at 9.51 GHz. In loaded condition, the resonant frequency of rectangular microstrip patch antenna reduces due to magnetic coupling. The dimensions of the antenna structure are 0.161 lambda x 0.192 lambda. Using the Chu limit, the size of the antenna comes to ka = 0.775, thus, satisfies the condition of an electrically small antenna (ka < 1). The antenna exhibits an impedance bandwidth of 512 MHz at a resonant frequency of 9.51 GHz. The calculated radiation Q(rad) is 18.86 which is larger than Q(chu) minimum, that is Q(chu) = 3.43. The gain and directivity of this antenna structure are 3.2 dBi and 7.8 dBi, respectively. The proposed antenna structure is simulated on a dielectric substrate with coaxial fed without incorporating any additional matching network.