A compact asymmetrically fed U shape slot antenna for 5G smartphone application is presented. The antenna consists of two major components that are responsible for generating broadband circular polarization (CP) (i) the microstrip patch feed structure employed at the top plane and (ii) U shape slot mechanism employed at the ground plane. The U shape ground radiator is approximately half wavelength slot mode which is responsible for lower band CP operation. The planar monopole structure is formed by the microstrip line feed. This planar monopole is a quarter wavelength mode used for achieving higher band CP operation. By combining these two CP modes generated by U shape slot and port-line structure, a broadband CP antenna is designed. The circular polarization is achieved with lesser complexity in the design structure. To get the practical validation of the simulated design, it is then fabricated and tested for measured results without using power divider. The measured axial ratio bandwidth covers from 2.00 GHz to 6.50 GHz (4.50 GHz) and the -10 dB Impedance Bandwidth (IBW) covers from 1.66 GHz to 8.10 GHz (6.44 GHz) respectively. The isolation between two asymmetric port-lines is greater than 14.5 dB within 3-dB axial ratio bandwidth.