Does a positive definite and radial function imply its Fourier transform is nonnegative?

• Bochner's theorem： In order that a function $$f:\mathbb{R}^d\rightarrow \mathbb{C}$$ be positive definite and continuous, it is necessary and sufficient that it be the Fourier transform of a nonnegative finite-valued Borel measure on $$\mathbb{R}^d$$.
But I have no idea to prove the Fourier transform of $$f$$ is positive. Any suggestions would be welcome! Thank you！