This paper presents a circular polarization plane antenna using linearly truncated triplate stripline resonator antenna. Glass-epoxy substrate is used in place of Teflon substrate for low cost fabrication. In spite the electrical dimension differs only √2 (root two), the dimensions of circular disk, its truncation, and feeding lines must be chosen precisely and accurately to get better characteristics of gain 12 dB compared to 10 dB by elliptic resonator with 4-antenna array.