A brain tumor is defined as a mass of tissue formed by an accumulation of abnormal cells within the brain. This paper proposes a high gain ultra-wideband (UWB) reflector array antenna for cancer detection. Introduction of the copper reflector with ideal distance contribute to increasing the proposed antenna gain. The antenna is printed with 4×1 copper radiating patch array properly connected with quarter wave transformer transmission line associated with a copper parasitic element for the front side. The patches comprise of four identical circulars with a diameter of 15 mm. Parasitic element is placed on very close to feeding line with the gap only 0.2 mm. Each quarter wave transmission line has its own specific wide dimension for 50Ω, 70.71Ω and 100Ω to ensure equal current distribution towards all four patches could be realized. Quarter-wave transformers of 70.71 Ω are used to have an ideal match between the 100 Ω lines and the 50 Ω lines. The high gain antenna is essential in a human microwave detection system for penetrating the multilayer structures by enhancing the focus of the electromagnetic energy into the desired structure. The antenna with reflector recorded wider bandwidth; 1.6 GHz-10.8 GHz associated with higher gain ranged from 3.2 dB until 14.1 dB compared with an antenna without reflector operated from 2.2 GHz to 10.8 GHz with lower gain ranges of 2.1 dB to 10.2 dB.
