Variations of Compact Rectangular Microstrip Antennas Using Defected Ground Plane Structure

Abstract

Abstract The defects in the form of slots have been employed in microstrip antenna either on the patch or the ground plane to yield frequency reduction. However, the reported work does not provide any comparative study that highlight upon the frequency and cross-polar level reduction achieved using these various shape slot/defects. This paper provides a thorough comparative study for different compact variations of microstrip antennas obtained using various shape slots on the ground plane. Amongst all, the optimum results are obtained for the bowtie-shaped slot on the ground plane, which offers cross-polar level reduction by 30 dB with a frequency reduction of 21%. The study also reveals that the slot on the ground plane offers better results against the slot on the patch in terms of frequency and cross-polar reduction. This kind of comparative study is not available in the literature and thus this is the novelty in the present work. An empirical formulation for the resonant length at the fundamental mode frequency for different shapes of slot/defect is proposed. The frequency calculated using them closely matches with those obtained using the simulation.

Keywords

• Compact Microstrip antenna
• Defected ground plane structure
• Impedance bandwidth
• Resonant length formulation
• Cross polar radiation