Functions on the real line with nonnegative fourier transforms

Unlike an integrable function on the unit circle which has the nonnegative Fourier coefficients and is square-integrable near the origin, an integrable function on the real line which has the nonnegative Fourier transform and is square-integrable near the origin is not always square-integrable on the real line. We give some examples, and consider an additional condition which guarantees the global square-integrability. Moreover, we treat an analogous problem for an integrable function on the real line which has non-negative wavelet coefficients of the Fourier transform and is squareintegrable near the origin.