Gain Enhancement of Microstrip Patch Array Antennas Using Two Metallic Plates for 24 GHz Radar Applications

In this paper, a method of enhancing gain in a microstrip patch array antenna using two metallic plates for 24 GHz radar applications is presented. A 4 x 1 linear microstrip square patch array antenna covering the 24.0 to 24.25 GHz frequency range and using a shunt-connected series feed network with a tapered power distribution was first designed with a measured maximum gain of 9.8 dBi and dimensions of 30 mm x 12 mm. Two metallic plates were appended along the array axis of the antenna to double the gain in the 4 x 1 array antenna. Effects on performance from varying the tilting angle and length of the metallic plates, such as the input reflection coefficient, the radiation patterns, and gain, were investigated through simulation. Gain enhancement in the 4 x 1 patch array antenna with metallic plates was highest when the tilting angle was around 70 degrees, and gain kept increasing as the length of the metallic plates increased. A prototype of the 4 x 1 patch array antenna was fabricated with plates at a tilting angle of 70 degrees, a length of 50 mm, and a measured maximum gain of 16.8 dBi. Therefore, a gain enhancement of about 7 dB was achieved by adding the metallic plates along the array axis of the 4 x 1 patch array antenna.