Inset microstripline-fed circularly polarized microstrip antennas

Circular polarization (CP) designs of inset microstripline-fed microstrip antennas are proposed. Three designs with a single slit, two pairs of slits, and three pairs of slits are experimentally studied. Good CP performances of the proposed antennas are achieved. For the design with three pairs of slits studied here, the center CP frequency is also seen to be lowered by about 33% compared to the case without slits, which suggests that an antenna size reduction as large as 55% can be obtained if the proposed design is used in place of a conventional CP design at a fixed frequency.