Utilization of LC Circuit as Impedance Matching for Spiral Resonator-based Planar Antenna

Some structures of metamaterials frequently implemented for miniaturizing a planar antenna are spiral resonator (SR) and split ring resonator (SRR). In fact, the SR structure has larger reduction factor compared to the SRR structure, however it is difficult to achieve an impedance match between the SR-based planar antenna and its feeding line. In this paper, therefore, a circuit configured by inductors and capacitors, namely LC circuit, is utilized as an impedance matching for SR-based planar antenna. Here, the proposed antenna is intended to operate at the frequency of 3.5GHz for fifth-generation (5G) cellular communication. To obtain a planar shape of LC impedance matching circuit, meandered inductors and interdigital capacitors are utilized as L and C components, respectively. The characterization results shows that the simulated and measured reflection coefficients (S
11
) for the proposed SR-based planar antenna with LC impedance matching circuit have good agreement with each other. In overall, the use of LC circuit as impedance matching can enhance the performances of SR-based planar antenna which are quite significant.