A dual-band wideband circularly polarized (CP) microstrip antenna is proposed for sub-6G application. The antenna consists of an upper L-shaped radiator and two circular strips on the ground. This produces the right-handed circular polarization (RHCP) in the Wi-Fi (2.4-2.48 GHz) and n77 (3.3-4.2 GHz) band with the help of two circular strips at the left and right corners on the lower ground. The antenna occupies a small radiating area of 45×45×1.0 mm3. The measured results show wide -10 dB reflection coefficient bandwidths of 46.4%（1.82-2.92 GHz）and 40.5% (3.15-4.75 GHz). The 3-dB axial ratio bandwidths of the antenna are 25.1% (1.88-2.42 GHz) and 40.6% (3.20-4.83 GHz). The measured peak gains are 4.8 and 7.5 dBi at the lower and higher bands, respectively. Therefore, the proposed antenna in this study is suitable for the dual-band wideband CP antenna as a reference.