Review of compact broadband circularly polarized microstrip antennas

In this paper, various compact techniques to reduce the size of the microstrip antennas (MSAs) for circular polarization (CP) have been explained. Square, circular and triangular shapes are used for size reduction. For compact operation square with four slots, corner truncated square MSA with bent slots, circle with cross-slot with peripheral cut and equilateral triangle with slits etc. are used. A square ring is fed at two orthogonal feed points with an offset polarizer inside the ring to realize compactness of 40%. Modified square MSA with four bent slots has a reduction of 52%. Circular MSA with cross-slot and peripheral cuts has a size reduction of 20%. Triangular with bent slots has a size reduction of 40%.