System and method for detecting a weak signal in a noisy environment

Systems and methods are disclosed for computing a power spectral density of a signal. One such method computes a Fast Fourier Transform (FFT) of a first signal segment and an FFT of a second signal segment. The first and second segments are adjacent and non-overlapping in time, and the second segment follows the first. The first FFT is multiplied by a complex conjugate of the second FFT. A first complex value is computed from this first product. An FFT of a third signal segment is computed. The second and third segments are adjacent and non-overlapping in time. The third segment follows the second segment. The second FFT is multiplied by a complex conjugate of the third FFT. A second complex value is computed from this second product. The first and second complex values are added, and the power spectral density of the sum is computed.