A low-cost patch array antenna for a high-sensitivity electromagnetic (EM) sensor is presented. The operating frequency band of the antenna is 24.05-24.25 GHz. Array structure is the symmetrical pattern by Chebyshev polynomial, and the feed point is located in the middle of the array. Also, the gain of the array antenna can be increased by controlling the inclined angle of the side wings, which are metal plates connected with the antenna ground plane. It was confirmed from the measurement results that the proposed antenna structure is very efficient to realize the high-gain performance in conformal size without variation of sidelobe level and return-loss characteristics.