5G stands for 5 th generation network. It allows to connect people, machines, objects, etc. this paper will be talking about the design of a simple rectangular microstrip patch antenna for Ka bands and mmW applications at 35 GHz as operating frequency with dimensions 4.4 x 3.05 mm2 and we got after simulation some parameters such as bandwidth equals to 4 GHz, 5.3 dB as Gain, 6.5 dB as Directivity, 1.9 as VSWR (Voltage Standing Wave Ratio). Then, we have tried to improve those parameters by doing another design known as U slot antenna and we have achieved, bandwidth equals to 3 GHz, 6.08 dB as Gain, 7.16 dB as Directivity, 1.3 as VSWR. The proposed antenna has been made using FR4 material for substrate and has successfully improved the values of parameters because efficiency is 85% and is suitable for 5G applications.