Endfire Antenna Array Using Microstrip-Fed Cavity-Backed Slot Elements

In this communication, an endfire antenna array using series-fed cavity-backed slot elements is proposed with low profile and high gain properties. By adopting the cavity-backed slot element as the radiating element, the antenna array can be partly embedded under the ground plane, which reduces the profile. Fed by an air-substrate microstrip line, the antenna array achieves a moderate phase constant, which leads to an endfire radiation pattern. By optimizing the coupling level between the cavity-backed slot elements and microstrip line, the aperture distribution of the antenna array is improved to enhance the endfire gain. With the overall length of 3.75 wavelength at 4 GHz, the proposed antenna array obtains a measured endfire gain of 11.5 dBi. Compared with the low-profile endfire antennas mounted on the metallic plane, the proposed antenna array has lower profile and higher endfire gain.