Investigation Into Circular Polarized Response of Square Microstrip Antenna using Defected Ground Structure

A square microstrip antenna with fractal defected ground structure is reported for the circularly polarized response. The reported configuration yields an impedance bandwidth of 30MHz and axial ratio bandwidth of 6 MHz. The gain across the axial bandwidth is varying between 1.7 to 2.2dBi. However, the stated work does not offer a clear insight of antenna functioning with respect to the main aspects of defected ground structure in terms of patch resonant modes, accountable for yielding circularly polarized response. Current manuscript gives an exhaustive investigation using resonance curves and vector current circulations with respect to circular polarization for reported configuration. From parametric investigations done, it is detected that defects created in the ground plane using fractal geometry, which is aligned exactly below the main patch, excites the orthogonal modes TM
⁴⁵
10 , and TM
¹³⁵
01 , that yields circular polarization. Further optimization of the same configuration is done on Arlon yielding impedance bandwidth of 104 MHz and AR bandwidth of 31 MHz.