Design of 2.5GHz and 24GHz Microstrip Antenna Arrays Using FR4 Substrates

The purpose of this thesis is to develop a 24 GHz antenna array using FR4 substrate in order to minimize the production cost. The 24 GHz antenna array will be applied in the automotive collision avoidance radar. The use of 2.5GHz antenna array is to verify the sequentially rotating array architecture. According to the frequency modulated continuous wave radar, increasing the operating bandwidth can improve the radar range resolution and speed resolution. The array element is a truncated microstrip antenna. The sequential rotation and phase feed antenna array is then applied to improve the axial ratio bandwidth and broadband impedance matching. The antenna array uses circular polarization in order to reduce the secondary reflection interference. λ/4 and 3λ/4 microstrip lines are used with proper feed lines to give a compact 2×2 sequential phase feed structure and reduce the side lobes. Two sequentially phase feeds are utilized to design a 4×4 24 GHz antenna array to increase the gain and reduce the 3dB beam width. Antenna arrays are measured using the far-field antenna measurement facility in EM group. The 4×4 antenna array gain is about 7.6 dB with 22° for 3dB beam width to indicate FR4 substrate can be applied in a low cost 24GHz car collision avoidance radar.