High Gain and Low Grating Lobe Electrically Large Array Antenna by Using Fabry-Perot Cavity

In this paper, a high gain and low grating lobe electrically large array antenna is proposed by using Fabry-Perot cavity (FPC). The feeding array antenna is composed by elements with electrically large property (ELP) based on TM30 mode. The FPC between a ground plane and a single-layer partially reflecting surface (PRS) made by substrate with arrays of square metal patches printed on both the top and bottom surfaces is used here to narrow the beamwidth of element patterns, thus the large grating lobes of array caused by large element spacing can be avoided. By analyzing the parameters of PRS unit cell, suitable cell spacing is determined. Finally, a 2 × 2 array was fabricated and measured to validate its effectiveness. Measurements demonstrate that the gain of the array can reach up 20.9dBi at the center working frequency. When the element spacing is 1.47λ0, the maximum grating lobe level at 21GHz is only -15.5dB.