We present a novel receiver structure for the detection and parameter estimation of linear frequency modulated signals. The proposed structure is based on the relations between the fractional Fourier transform and the ambiguity function. It has been shown that the optimal ML receiver, which is the peak detector in the ambiguity plane, can be implemented at a reduced search complexity with the proposed method. The proposed method uses two 1-dimensional search operations in two different fractional Fourier domains instead of a 2-dimensional search over the ambiguity plane. The performance of the method is illustrated with an example.